FOR OFFICIAL USE ONLY
Developing a Roadmap for
Improving Water Quality of Lake
Toba Tourist Destination, Indonesia
Final Report – Final Draft
Prepared by Deltares for the World Bank upon the request of Indonesia’s Coordinating
Ministry of Maritime Affairs and the Ministry of Public Works and Housing This work received financial support from Australian Government through the Indonesia Infrastructure Support Trust Fund (INIS TF)
This document has a restricted distribution and may be used by recipients only in the performance of their official duties. Its contents may not otherwise be disclosed without World Bank authorization.
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Key Messages
Tourism is a promising growth sector in Indonesia that can provide inclusive and sustainable
opportunities for economic development. The archipelago is home to one of the most biodiverse
habitats in the world having a rich array of tourism endowments that form the underlying
attraction for visitors. Indonesia has expanded the promotion of its natural resources by
increasing the size of protected areas and attracting more online interest in nature. Despite this,
Indonesia’s tourism industry is not operating at a level consistent with the quality and diversity
of its natural and cultural endowments, with environmental sustainability a key risk factor for
the sector (WEF, 2017).
Four key constraints contribute to Indonesia not fulfilling its tourism potential. These include: (i)
continued poor access to, and quality of, infrastructure and services for citizens, visitors and
businesses; (ii) limited tourism workforce skills and private-sector tourism services and facilities
outside of Bali; (iii) weak enabling environment for private investment and business entry; and
(iv) poor inter-ministry/agency, central-local and public-private coordination and weak
implementation capabilities for tourism development in general, and for monitoring and
preservation of natural and cultural assets in particular.
In response, the Government has launched the Indonesia Tourism Development Priority
Program. For the implementation of the program, the Government has decided to sequence
the development of tourism destinations, starting with three priority destinations: Lombok in
West Nusa Tenggara province; Borobudur-Yogyakarta-Prambanan in Central Java province
and the Special Region of Yogyakarta; and Lake Toba in North Sumatra province. If developed
effectively, these three distinctively different and unique destinations are expected to increase
their combined annual foreign and domestic visitor expenditures from an estimated US$1.2
billion in 2015 to US$1.5 billion in 2021 and US$2.0 billion in 2026 (Horwath, 2017).
The objective of this report is to prepare a Roadmap for Improving Water Quality of Lake Toba
as a Tourism Destination. It provides an understanding of the key drivers of water quality issues
and investment scenarios to reduce nutrient loads into the lake. These are intended to inform
the preparation of an Integrated Tourism Master Plan to provide a stronger framework for
effective and sustainable tourism development.
Lake Toba is the largest volcano tectonic lake in the world and one of Indonesia’s priority
tourism destinations. However, Lake Toba is largely a destination for local tourism with
declining appeal. With improvements in accessibility, recreational activities and environmental
sustainability, Lake Toba can become an attractive destination for a much wider variety of
domestic and international visitors.
The water quality of Lake Toba is under threat from eutrophication. Science informed policy
measures have established the desired lake quality as oligotrophic. However, the current state
is mesotrophic for phosphorous and chlorophyll. This leads to local effects such as algal blooms
that harm the tourism sector. This eutrophication is mainly driven by residues from aquaculture
(68% of total phosphorous load and 76% of total nitrogen). Other contributors include livestock
(19% of phosphorous and 5% of nitrogen) and domestic wastewater (11% of phosphorous and
15% of nitrogen).
Aquaculture production is far in excess of the legally established carrying capacity. Whole lake
estimates based on numerous scientific studies have established the carrying capacity for
aquaculture at 10,000 tons. While aquaculture is a relatively recent economic activity in Lake
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Toba, the rapid expansion of large commercial ventures and local producers since the 1990s
has resulted in thousands of floating fish cages in the lake, with 2015 production estimated
around 85,000 tons. Not all aquafarms are operating within the legal framework with poor inter-
ministry/agency, central-local and public-private coordination and weak implementation
capabilities for monitoring and preservation undermining the natural and cultural assets of Lake
Toba.
A compartmentalized approach to modelling the water quality of Lake Toba provides new
insights into the functioning and drivers of water quality. Four theoretical compartments have
been defined based on topography and bathymetry. This includes one northern and three
southern compartments. These compartments provide a differentiated assessment of the key
drivers associated with water quality in Lake Toba. These can be further refined based on a
continuous process of improvement informed through better data. Results show that targeted
strategies are required to achieve local impacts and for monitoring and management of water
quality interventions.
While an integrated approach to water management is required for Lake Toba, water quality
cannot be improved without reducing the current production of aquaculture. Four scenarios
have been modelled to compare the impact of low, intermediate and high levels of investment
intended to impact the nutrient loads into Lake Toba. Only by reducing aquaculture in the lake
to a total production level of no more than 10,000 tons per year can water quality in the lake be
expected to recover to an oligotrophic state.
Aquaculture can be reduced mainly by limiting licenses and by improving law enforcement. This
should be supported by training in alternative livelihoods such as organic farming and fisheries.
The estimated total costs over five years would be IDR 9.7 billion (US$ 719,000) under an
intermediate scenario, gradually bringing down fish production, and IDR 34.2 billion (US$ 2.5
million) under a high investment scenario to reach the target of 10,000 tons of fish per year in
2022. Crucial to the success of these measures is the political commitment to change the
licensing structure and implement more stringent law enforcement.
Such a strategy will have different impacts for different districts in Lake Toba, with the districts
benefiting from increased tourism growth and the districts being affected by reduced
aquaculture not always being the same. Similarly, tourism job gains and aquaculture job losses
might be distributed unevenly. The government’s agenda thus requires recognition and
quantification of trade-offs, which can be eased by measures, such as revenue-sharing
arrangements between districts, intensified training opportunities and a phased, rather than
abrupt change of policy.
Nutrient loads can be further reduced through interventions in processing livestock manure and
domestic wastewater management to further strengthen the impact of measures implemented
in the aquaculture sector. The conversion of livestock manure into biogas would require IDR
12.9 billion (US$ 957,000) for five years under an intermediate scenario, aiming for 20%
conversion by 2022 or IDR 18.8 billion (US$ 1.4 million) under a high investment scenario
resulting in 30% conversion.
Implementation of the national sanitation strategies could accelerate the construction of
individual and community-based on-site septic tank systems with positive benefits for longer
term water quality. An intermediate scenario would provide 85% of the population in the
catchment area of Lake Toba with septic tank systems by 2022. This would require an extra
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investment of IDR 694.6 billion (US$ 51.5 million). A high investment scenario would provide
access to centralized sewer-based systems for 31% of the population. Its costs would be IDR
3,866.9 billion (US$ 286.5 million).
The targeted oligotrophic status can only be achieved through an integrated management plan
under a high investment scenario. Total net investment costs for this scenario would be IDR
3,919.8 billion (US$ 290.5 million) for five years. While the biggest impacts would be realised
through improved regulation of aquaculture, the majority of these investments would be in water
supply and sanitation. The impacts of these interventions on nutrient concentrations would be
different for each of the compartments. In the southern part of Lake Toba, the oligotropic state
would be achieved in 2022, except for the smallest and most intensively used compartment
west of Samosir. This part of the lake would stay eutrophic even under high investment
scenarios, unless additional efforts are deployed to reduce nutrient loads from domestic
wastewater and livestock. In the northern part of the lake, concentrations would eventually
reach low mesotrophic levels, approaching the oligotrophic limit of 10 µg per litre. The
intermediate scenario, at a cost of IDR 717.2 million (US$ 53.0 million) for the first five years,
would achieve these results only in 2042. In 2022 the intermediate scenario would not result in
long term oligotrophic state in any of the compartments.
A cost-efficient approach would be a combination of options; selecting high investment
interventions for aquaculture and livestock, combined with intermediate interventions for
wastewater. This combination would cost IDR 747.5 billion (US$ 55.4 million), reducing the
public investment costs by IDR 3.17 billion (US$235 million) as compared to the high
investment scenario, while impacts on water quality would still be high because of the
substantial reduction in nutrients due to aquaculture.
A comprehensive water quality monitoring program is required to assess long term trends in
Lake Toba and to inform an adaptive management approach. This should be based on
collaboration aligned with institutional responsibilities and free open source data sharing. When
combining the existing activities of the main water quality monitoring institutions, a
comprehensive approach can be achieved, including signal, exploratory and statistical
functions. This should include regular sampling and analysing a range of variables for
background monitoring and depth profiles, at no less than forty stations distributed across the
lake. It is estimated to cost a minimum of IDR 20.4 billion (US$ 1.5 million) annually, or IDR
102 billion (US$ 7.6 million) over 5 years. A more aspirational program building on latest
technologies and involving stakeholders is estimated to cost around IDR 92.3 billion (US$ 6.8
million) per year, amounting to IDR 462 billion (US$ 32.4 million) over 5 years.
Sustained political commitment across all levels of government and sectoral coordination
among different stakeholders will be essential to realising the government’s agenda for
improving the water quality and tourism value of Lake Toba. Such an approach needs to be
supported by a water quality and waste load monitoring program. This could continuously
assess the impact of interventions under the Integrated Management Plan and to enable
adaptive actions during implementation. Together, the proposed interventions and monitoring
plan would guide the integrated management of water quality in Lake Toba and support the
contribution of Lake Toba to the economic and social development of Indonesia and serve as
an example for the management of other lake basins.
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Contents
Executive Summary
Acronyms
Glossary
1 Introduction 1 1.1 Background 1
1.1.1 Water quality concerns at Lake Toba 1 1.1.2 Rationale for roadmap 2
1.2 Objective and approach 3 1.2.1 Stakeholder consultations 4 1.2.2 Reference Group 4
1.3 Overview 5
2 Lake Toba as a Tourism Destination 7 2.1 Lake Toba and its surroundings 7
2.1.1 Topography 7 2.1.2 Climate 8 2.1.3 Land-use practises and spatial development 8 2.1.4 Economy 10 2.1.5 Batak culture 14
2.2 Catchment hydrology and functioning of Lake Toba 15 2.2.1 Catchment dimensions and water level 15 2.2.2 Catchment erosion 16 2.2.3 Biogeochemical processes in Lake Toba 17 2.2.4 Residence time and recovery time of Lake Toba 17 2.2.5 Stratification 17 2.2.6 Horizontal lake circulation and zonation 19
2.3 Key factors of Lake Toba water quality problems 22
3 Legal and Institutional Environment 27 3.1 Approach 27 3.2 Standards for monitoring 27
3.2.1 Oligotrophic status and class 1 standard 29 3.2.2 Aquaculture Stewardship Council (ASC) Standards 30
3.3 Institutional arrangements for monitoring 31 3.3.1 Provincial Environment Department – North Sumatra (DLH-SU) 31 3.3.2 Indonesian Institute of Sciences (LIPI) 33 3.3.3 River Basin Operator (PJT1) 34 3.3.4 PT Aquafarm Nusantara (PTAN) 35
3.4 Legal arrangements for water quality management 36 3.4.1 Provincial setting 38 3.4.2 National setting 38 3.4.3 International setting 40 3.4.4 Licensing and permits 41
3.5 Legislation vs implementation 43
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4 Stakeholders and Governance 45 4.1 Approach 45 4.2 Stakeholder mapping 45
4.2.1 Mapping 45 4.2.2 Key stakeholders 48
4.3 Stakeholder assessment 52 4.4 Governance for monitoring and management of Lake Toba 53
4.4.1 Approach 53 4.4.2 Overall SWOT 53 4.4.3 Synthesis 56
5 Drivers and Pressures: nutrient inputs 57 5.1 Approach: the Sumatra Spatial Model 57
5.1.1 Calibration of population growth 57 5.1.2 Load calculations 57
5.2 Assessment of point and non-point sources 59 5.3 Total and relative nutrient loads 64 5.4 Nutrient inputs 70
6 State and Impact: Lake Assessment 71 6.1 Approach 71 6.2 Available data 71
6.2.1 Main data sets 71 6.2.2 Quality of data 72
6.3 Physical and chemical parameters 73 6.3.1 Temperature 74 6.3.2 Dissolved Oxygen (DO) 76 6.3.3 Transparency (Secchi depth) 78
6.4 Nutrients 79 6.4.1 Phosphorous 79 6.4.2 Nitrogen 80
6.5 Organic content 81 6.6 Thermocline depth 82 6.7 Remote sensing insights into water quality dynamics 83 6.8 Hydrothermal stability and mixing events 85 6.9 Trends 89
6.9.1 Present data vs historical data 89 6.9.2 The 2016 anomaly 90
6.10 Lake status 91
7 Future Pressures and Future State 95 7.1 Approach 95 7.2 Input data 95
7.2.1 Population and economic growth drivers 95 7.2.2 Spatial plan 97
7.3 Projections in the Sumatra Spatial Model 99 7.3.1 Population projection 100 7.3.2 Land use change projection 101 7.3.3 Tourism 103
7.4 Nutrient concentration trajectories 103
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8 Response: water quality management 107 8.1 Approach 107 8.2 Aquaculture 111
8.2.1 Investment scenario 111 8.2.2 Impact on nutrients 116
8.3 Managing livestock manure 120 8.3.1 Investment scenarios 120 8.3.2 Impacts on nutrients 122
8.4 Wastewater (domestic and tourism) management 125 8.4.1 Approach and background 125 8.4.2 Investment scenarios 126 8.4.3 Impact on nutrients 130
8.5 Other interventions 134 8.5.1 Pollution in agriculture 134 8.5.2 Solid waste management 134 8.5.3 Erosion reduction 136
8.6 Cumulative impact of scenarios 138 8.6.1 Four scenarios 138 8.6.2 Alternative scenario 144
9 Response: water quality monitoring 149 9.1 Three pillars 149
9.1.1 System knowledge 150 9.1.2 Information needs 151 9.1.3 Technical capabilities 152 9.1.4 Incorproating remote sensing capabilities 152 9.1.5 Requirements 153 9.1.6 Data collection: Common sources of error 154
9.2 Monitoring working group 155 9.3 Monitoring parameters 158 9.4 Investment scenario 161
10 Summary results, conclusions and recommendations 165 10.1 Drivers of lake eutrophication 166 10.2 Status and functioning of Lake Toba 166
10.2.1 Historical and current lake status 167 10.2.2 Lake functioning 167
10.3 Water quality monitoring 168 10.3.1 Data assessment 168 10.3.2 Towards a water quality monitoring plan for Lake Toba 170
10.4 Water quality management 171 10.4.1 Potential of interventions 171 10.4.2 Reducing nutrient loads from aquaculture 174 10.4.3 Managing livestock manure 174 10.4.4 Wastewater management 175 10.4.5 Total investment costs for mitigating measures 176 10.4.6 Mitigation options and effects on eutrophication 178
10.5 Investments for impact 181
11 References A-1
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Appendices
A Stakeholder consultation process A-6 A.1 Reference Group A-6 A.2 Meetings A-7
A.2.1 Stakeholder meetings A-7 A.2.2 Individual meetings A-8
B Detailed description of Lake Toba B-1 B.1 Bathymetry B-1 B.2 Hydrological and administrative boundaries B-2 B.3 Soil B-2 B.4 Climate B-3 B.5 Water level B-5
C Background on functioning of lakes C-1 C.1 Theory of residence time C-1 C.2 Theory of biochemical processes C-1 C.3 Trophic level classification C-3
D Background on DPSIR D-1
E Institutional assessment E-1
F Overview of relevant legislation F-1 F.1 List of laws in English F-1 F.2 List of laws in Bahasa Indonesia F-2
G Water quality data PJT1 G-1
H Methodology of stakeholder assessment H-1 H.1 Theoretical framework H-1
H.1.1 Stakeholder roles and functions H-1 H.1.2 Social network analysis H-3
H.2 Methods and tools H-4 H.2.1 NetMap H-4
H.3 Stakeholder perceptions H-7 H.3.1 Observations from NetMap discussions H-7 H.3.2 Summary of stakeholder comments H-8
I Comprehensive list of stakeholders involved in Lake Toba water quality I-1
J Detailed methodology lake assessment J-1 J.1 Sumatra Spatial Model J-1
J.1.1 Introduction J-1 J.1.2 Land use changes J-4
J.2 Modules and variables J-5 J.2.1 Regional or Socio-economic sub-model J-6 J.2.2 Spatial allocation sub-model J-7
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J.2.3 Postprocessor for space, water and agricultural indicators J-8 J.3 Spatial results by compartment and year J-9 J.4 Calculation of nutrient concentration trajectories J-13 J.5 Comparison to LIPI data J-14
K Available data and their quality K-1 K.1 Data collected from stakeholders K-1 K.2 Completeness of the data sets K-6 K.3 Spatial and temporal distribution of data K-9
L Additional recommendations livestock L-10 L.1 Steps in managing livestock manure L-10 L.2 Promotion of biogas production L-10 L.3 Sustainable manure management L-11
M Background information wastewater interventions M-13 M.1 Background and approach M-13 M.2 Investment scenarios M-17 M.3 Parapat M-21 M.4 Institutional recommendations on wastewater management M-22
M.4.1 General considerations M-23 M.4.2 Policy actions M-23 M.4.3 Technical assistance M-26 M.4.4 Other recommendations M-27
N Other sectors N-1 N.1 Solid waste N-1
N.1.1 Approach and background N-1 N.1.2 Investment scenarios N-5 N.1.3 Conclusions and recommendations N-10
N.2 Erosion reduction N-10 N.2.1 Background N-10 N.2.2 Investment scenarios N-11
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Foreword [Foreword will be added to edited version]
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Acknowledgements This Development of a Roadmap for Improving the Water Quality of Lake Toba as a Tourist Destination is one of a series of products aimed at supporting the preparation of the Government of Indonesia Tourism Development Project. The World Bank team was led by Marcus Wishart (Senior Water Resources Management Specialist), Bertine Kamphuis (Senior Private Sector Specialist), and Amy Chua Fang Lim (Environmental Specialist), included Aleix Serrat-Capdevila (Senior Water Resources Management Specialist), Ivan Lalovic (Remote Sensing and Water Quality Specialist), Fernando Wilhelm (Remote Sensing and Water Quality Specialist), and benefitted from inputs from George Soraya (Lead Municipal Engineer), Evi Hermirasari (Senior Urban Development Specialist), and Muhammad Halik Rizki (Urban Planning Analyst). The analysis and model development were undertaken by Deltares and partners, led by Eline Boelee and included JanJaap Brinkman, Gertjan Geerling, Tineke Troost, Henni Hendarti, Bastien van Veen, Muhammad Fitranatanegara, Christophe Thiange, Rob Uittenbogaard, Bouke Ottow, Simon Groot, Annemiek Mertens (all Deltares), Hanny Chrysolite, Satrio Wicaksono, Arief Wijaya (all WRI Indonesia), Koen Broersma, J Sinarko Wibowo, Arina Priyanka Vedaswari, Hari Meidiyanto, Suhendi, Marco Piët (all Royal Haskoning DHV), as well as Poul Grashoff, Douglas Vermillion, and Robert Belk. The program was implemented under the guidance of Rodrigo A. Chaves (Country Director) and Ganesh Rasagam (Practice Manager) of the World Bank. The roadmap has been prepared upon the request of Indonesia’s Coordinating Ministry of Maritime Affairs and the Ministry of Public Works and Housing. The Coordinating Ministry of Maritime Affairs was led by Ridwan Djamaluddin (Deputy Minister for Infrastructure) and included Rahman Hidayat (Director for Infrastructure of Shipping, Fishery and Tourism) and Velly Asvaliantina (Deputy Director for Marine Tourism Infrastructure). Other Indonesian government agencies participating in the study included: 1. Fauzan Ali and Lukman (Centre of Limnology, Indonesian Institute of Sciences) 2. Rudi Nugroho, Titin Handayani, Nawa Suwedi and Agung Riyadi (Centre of Environmental
Technology, Agency for the Assessment and Application of Technology) 3. Budi Kurniawan (Directorate for Water Pollution Control, Ministry of Environment and
Forestry) 4. Hermono Sigit (Directorate for Watershed and Aquatic Management, Ministry of
Environment and Forestry) 5. Hidayati, Siti Bayu and Fauzi Tarigan (North Sumatra Provincial Environmental Agency) 6. Baru Panjaitan, Novita R and Serepita Sinurat (Basin Management Centre Sumatra II) 7. Arie Prasetyo (Head of Lake Toba Tourism Area Management Authority Board) 8. Raymond Tirtoadi (Centre for Strategic Areas, Ministry of Public Works and Housing) 9. Astria Nugrahany (Perum Jasa Tirta I)
This publication has been funded by the Australian Government through the Department of Foreign Affairs and Trade. The views expressed in this publication are the author’s alone and are not necessarily the views of the Australian Government.
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Acronyms
List of abbreviations, acronyms and Indonesian terms
Abbreviation/
Indonesian term
Meaning/translation
Alusi Tao Toba A local foundation in North Sumatra working mainly in the education
sector
ASC Aquaculture Stewardship Council: Dewan Pengelolaan Budidaya
Perikanan
Asosiasi Nelayan Asosiasi Nelayan/Budidaya: Fishermen Association
ATAB Air Tanah dan Air Baku – Kementerian Pekerjaan Umum dan
Perumahan Rakyat: Ground Water and Raw Water Division under
the Ministry of Public Works and Housing
ATR Kementerian Agraria dan Tata Ruang: The Ministry of Agrarian
and Spatial Planning
Badan Pengelola
GEOPARK
GEOPARK Management Agency
Balai PSDA Balai Pengelolaan Sumber Daya Air: River Basin Organisation (at
provincial level)
BAPPEDA PROV Badan Perencana Pembangunaan Daerah Provinsi: Provincial
Planning Agency
BAPPEDA KAB Badan Perencana Pembangunan Daerah Kabupaten: District
Planning Agency
BAPPENAS Badan Perencanaan Pembangunan Nasional: National
Development Planning Agency
Batak A collective term to identify a number of ethnic groups
predominantly found in North Sumatra
BBWS Balai Besar Wilayah Sungai: River Basin Organisation (at national
level)
BIG Badan Informasi Geospasial: Geospatial Information Agency
BKPEDT Badan Koordinasi Pelestarian Ecosistem Danau Toba:
Coordinating Agency for Lake Toba Ecosystem
Conservation/Environmental Sustainability Authority Lake Toba
BKPM Badan Koordinasi Penanaman Modal: Investment Coordinating
Board
BLH(-SU) Badan Lingkungan Hidup (-Sumatra Utara): Provincial
Environment Agency (- North Sumatra) from January 2017: DLH
BLU Badan Layanan Umum: Public service organization
BMKG Badan Meteorologi, Klimatologi dan Geofisika: Indonesian Agency
for Meteorological, Climatological and Geophysics
BNPB Badan Nasional Penanggulangan Bencana: The Indonesian
National Board for Disaster Management
BOD Biochemical oxygen demand
BOPDT/
BOPKPDT
Badan Otorita Pariwisata Danau Toba/ Badan Otorita Pengelola
Kawasan Pariwisata Danau Toba: Lake Toba Tourism Area
Management Authority, established through Presidential
Regulation 49/2016
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Abbreviation/
Indonesian term
Meaning/translation
BPBD Badan Penanggulangan Bencana Daerah: Local Agency for
Disaster Management
BPDAS Badan Pengelola Daerah Aliran Sunga: Watershed Management
Agency (under KLHK)
BPIW Badan Pengembangan Infrastruktur Wilayah: Regional
Infrastructure Development Agency (Ministry of Public Works and
Housing
BPN-ATR Badan Pertanahan Nasional AgrariaTata Ruang: National Land
Agency, Agrarian and Spatial Planning Ministry
BPPT Badan Pengkajian dan Penerapan Teknologi: Agency for the
Assessment and Application of Technology
BPS Biro Pusat Statistik: Statistics Indonesia
BPS Buku Putih Sanitasi: Sanitation strategy for city or district
BTA 155 Bilateral Technical Assistance 155 (Cisadane-Cimanuk Integrated
Water Resources Development project), embryo of Pola and
Rencana (1985 –1991)
BTPAL Balai Teknologi Pengolahan Air dan Limbah: Organisation for
Technology of Wastewater Treatment (BPPT)
Bupati Head of district
BWRMP Basin Water Resources Management Plan (2001-2004):
Perencanaan Pengelolaan Sumber Daya Air Wilayah Sungai
BWRP Basin Water Resources Planning (1996-2001), later changed to
BWRMP: Perencanaan Sumber Daya Air Wilayah Sungai
BWS-S2
BWS-Sumatera II
Balai Wilayah Sungai Sumatera II: River Basin Organisation -
Sumatra II
CAPEX Capital investment costs
COD Chemical oxygen demand
CSO Civil society organization: Lembaga Swadaya Masyarakat
Daerma A fishermen’s association
Dewan SDA Provinsi Dewan Sumber Daya Air Provinsi: Provincial Water Resources
Council
DGWR Direktorat Jenderal Sumber Daya Air, Kemen (PUPR): Directorate
General for Water Resources under Ministry of Public Works and
Housing
Dinas Cipta Karya
Prov.
Dinas Cipta Karya: Provincial Human Settlements Agency
Dinas Cipta Karya
Kab.
Dinas Cipta Karya Kabupaten: District Human Settlements Agency
Dinas ESDM Dinas Energi dan Sumber Daya Mineral Daerah: Energy and
Mineral Resources Agency
Dinas BINA MARGA
PROV
Provincial Highway Engineering Services
Dinas Kehutanan
Prov.
Dinas Kehutanan: Provincial Forestry Agency
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Abbreviation/
Indonesian term
Meaning/translation
Dinas Kehutanan
KAB
Dinas Kehutanan Kabupaten: District Forestry Agency
Dinas Kesehatan
Kab.
Dinas Kesehatan Kabupaten: District Health Agency
Dinas Lingk. Hidup
Daerah
Dinas Lingkungan Hidup Daerah: District Environmental Agency
Dinas Pariwisata
Prov
Dinas Pariwisata: Provincial Tourism Agency
Dinas Pariwisata
Kab.
Dinas Pariwisata Kabupaten: District Tourism Agency
Dinas Pemukiman
Tata Ruang
Dinas Pemukiman Tata Ruang: Human Settlements Spatial
Planning Agency
Dinas Perhub Dinas Perhubungan: Transportation Agency
Dinas Perijinan Prov. Dinas Perijinan: Provincial Licensing Agency
Dinas Perijinan
Daerah Kab.
Dinas Perijinan Daerah Kabupaten: District Licensing Agency
Dinas Perikanan
Prov.
Dinas Perikanan: Provincial Marine and Fisheries Agency
Dinas Perikanan
Kelautan Kab.
Dinas Perikanan Kelautan Kabupaten: District Fisheries and
Extension Agency
Dinas Pertanian Prov. Dinas Pertanian: Agriculture Provincial Agency
Dinas Pertanian Kab. Dinas Pertanian Kabupaten: District Agriculture Agency
Dinas Peternakan
Kab.
Dinas Peternakan Kabupaten: District Livestock Agency
Dinas PUP or SDA Dinas PU/SDA Provinsi (PU Pengairan): Provincial Water
Resources Service
Dinas Tanaman
Pangan dan
Holtikultura
Dinas Tanaman Pangan dan Holtikultura: Food Crops and
Horticulture Agency
Dir. Jenderal BINA
MARGA
Directorate General Highway Engineering (Ministry of Public
Works and Housing)
Dir. Sungai Pantai
PUPR
Direktorat Sungai dan Pantai – Kementerian Pekerjaan Umum dan
Perumahan Rakyat: Directorate of Coastal River (Ministry of Public
Works and Housing)
Ditjen Perikanan
Budidaya
Directorate General of Aquaculture and Fisheries
DLH(-SU) Dinas Lingkungan Hidup (-Sumatra Utara): Provincial Environment
Department (- North Sumatra)
DMI Domestic, Municipal and Industrial (Water Demand): Rumah
Tangga, Kota dan Industri (Kebutuhan Air)
DMO Toba Destination Management Organization Toba:
DO Dissolved oxygen
DPSIR Driver, Pressure, State, Impact, Response concept
DSS Decision Support System, such as RIBASIM: Sistem Pendukung
Pengambilan Keputusan
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Abbreviation/
Indonesian term
Meaning/translation
DTA (Lake Toba) Daerah tangkapan Air (Danau Toba): Danau Toba Area or catchment area (Lake Toba)
ESDM Kementerian Energi dan Sumber Daya Mineral: Ministry of Energy
and Mineral Resources
Forum DAS Forum Daerah Aliran Sungai: Watershed Forum
Forum Komunikasi
Toba
Forum Komunikasi Danau Toba: Lake Toba Communication
Forum
FEWS/HYMOS Hydrological data processing system based on Flood Early
Warning System/Hydrological Modelling System: Proses Data
Hidrologi berdasarkan Sistem Peringatan Dini Untuk Banjir/Sistem
Pemodelan Hidrologi
FMSB Flood Management in Selected Basins (2004 – 2005):
Pengelolaan Banjir untuk Wilayah Sungai Terpilih
Germadan Gerakan Penyelamatan Danau: Lake Rescue Initiative
GFW Water Global Forest Watch Water
GGN Global Geopark Network
GIS Geographic Information System: Sistem Informasi Geografik
GOI Government of Indonesia: Pemerintahan Indonesia
Harian Analisa North Sumatra-based newspaper
HRM Human Resources Management: Pengelolaan Sumber Daya
Manusia
ICWRMIP Integrated Citarum WRM Investment program: Program Investasi
Sumber Daya Air Terpadu Citarum
IDBP Indonesian Domestic Biogas Programme
IFI International Financing Institution
(PT) INALUM PT Indonesia Asahan Alumunium; a state-owned company in the
aluminium industry (owner of hydroelectric power plant along
Asahan river)
(PT) INHUTANI Perusahaan Umum (PERUM) Perhutani: National Corporation for
Forestry (INHUTANI IV for North Sumatra)
IPAL Instalasi Pengolahan Air Limbah: wastewater treatment plant
IPLT Instalasi Pengolahan Lumpur Tinja: sewage sludge treatment plant
ISO International Organization for Standards
IWRM Integrated Water Resources Management: Pengelolaan Sumber
Daya Air Terpadu
JABO(DE)TABEK Area comprising (Daerah) Jakarta, Bogor, (Depok), Tangerang,
Bekasi
JSM Java Spatial Model: Model Spasial Jawa
Jurung A local fish
JWRMS Jakarta Bogor Tangerang Bekasi Water Resources Management
Study (1991 – 1995): Studi Pengelolaan Sumber Daya Air
JABOTABEK
JWRSS Java Water Resources Strategic Study (2010 – 2012): Studi
Strategis Sumber Daya Air (pulau) Jawa
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Abbreviation/
Indonesian term
Meaning/translation
Kabupaten/Kota District/City, autonomous administrative level within the province
Kantor Pertanahan
Kab./Kota
Kantor Pertanahan Kabupaten/Kota: District/City Land Office
Kecamatan Sub-district
Kelompok
Keagamaan
Religious group
Kel. Sadar Wisata Kelompok Sadar Wisata: Local tourism group
Kel. Tani Kelompok Tani: Farmers group
Kemen. Pariwisata Kementerian Pariwisata: Ministry of Tourism
Kemen. ESDM Kementerian Energi dan Sumber Daya Mineral: Ministry of Energy
and Mineral Resources
Kemenaker Kementerian Ketenagakerjaan: The Ministry of Manpower
Kemendagri Kementerian Dalam Negeri: The Ministry of Internal Affairs
Kemendus Kementerian Perindustrian: The Ministry of Industry
Kemenhub Kementerian Perhubungan: The Ministry of Transportation
Kemenkeu Kementerian Keuangan: The Ministry of Finance
Kemenko Ekonomi Kementerian Koordinator Bidang Perekonomian: Coordinating
Ministry of Economic Affairs
Kemenko Maritim Kementerian Koordinator Bidang Kemaritiman: Coordinating
Ministry of Maritime Affairs
Kemenpan Kementerian Pendayagunaan Aparatur Negara dan Reformasi
Biro: The Ministry of Administrative and Bureaucratic Reform
Kementan Kementerian Pertanian: The Ministry of Agriculture
KJA Keramba Jaring Apung: floating fish cages
KKP Kementerian Kelautan dan Perikanan: The Ministry of Marine
Affrairs and Fisheries
KLHK Kementerian Lingkungan Hidup dan Kehutanan: The Ministry of
Environment and Forestry
Kom. Transportasi Air Komunitas Transportasi Air: Water Transportation Community
Kom. Adat Komunitas Adat: Indigenous Community
Kom. Hutan Komunitas Hutan: Forestry Community
Kom. Pariwisata Komunitas Pariwisata: Tourism Community
Kom. Sungai Komunitas Sungai: River Community
Komisi Irigasi Komisi Irigasi: Irrigation Commission
KPTS Keputusan: decree (decision)
KSM Kelompok Swadaya Masyarakat: Local community support group
KSN Kawasan Strategi Nasional: National Strategic Region (NSR)
KSP Kantor Staff Presiden: President’s Office
KSPPM Kelompok Studi dan Pengembangan Prakarsa Masyarakat; Study
Group and Community Initiative Development
LIPI Lembaga Ilmu Pengetahuan Indonesia: Indonesian Institute of
Sciences
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Abbreviation/
Indonesian term
Meaning/translation
LMA Badan Otorita Pengelola Kawasan Parawisata Danau Toba: Lake
Toba Tourism Area Management Authority (the Lake Management
Authority)
LTEMP Lake Toba Ecosystem Management Plan: Rencana Pengelolaan
Ekosistem Danau Toba
LSM Lembaga Swadaya Masyarakat: Civil Society Organization, Non-
Governmental Organization
MFF Multi-tranche Financing Facility (for ADB loans): Fasilitas
Pembiayaan Multi Tranche
MIS Management Information System: Pengelolaan Sistem Informasi
MOHA Ministry of Home Affairs: Kementerian Dalam Negeri
MPS Memorandum Program Sanitasi: Agreed Sanitation Program
MPW Ministry of Public Works: Kementerian Pekerjaan Umum
N nitrogen
NGB Pangambatan, a location of PT Aquafarm Nusantara
NGO Non-Governmental Organization: Lembaga Swadaya Masyarakat
NRW Non-Revenue Water: water distributed by PDAM, but not paid for
NSR National Strategic Region: Kawasan Strategi Nasional (KSN)
O&M Operation and Maintenance: Operasi dan Pemeliharaan
OPEX Operational expenses, running costs
P phosphorous
Palawija Staple crops other than rice (coarse grains, pulses, roots and
tubers)
PDAM Perusahaan Daerah Air Minum: Regional Water Supply Company
PE Political Economy: Ekonomi Politik
PEA Political Economic Assessment: Kajian Ekonomi Politik
Penambang Galian C Penambang Galian: Mining Company
Perpres Peraturan Presiden: Presidential Regulation
Peternak Livestock Farmers
PHT Panahatan, a location of PT Aquafarm Nusantara
PIU Project Implementation Unit: Unit Pelaksana/Implementasi Proyek
PJT1 and PJT2 Perusahaan Umum (PERUM) Jasa Tirta: National Corporation for
Basin Management (I for Brantas, Bengawan Solo and Toba
Asahan and others, II for Citarum)
PKK Pembinaan Kesejahteraan Keluarga: Family welfare management
PLTA Renun Pembangkit Listrik Tenaga Air: Hydropower plant in the village of
Renun
PMU Project Monitoring Unit: Unit Pemantauan/Monitoring Proyek
Pola Rencana Framework for strategic management plans
PPSP Program Nasional Percepatan Pembangunan Sanitasi
Permukiman: National Accelerated Sanitation Development for
Human Settlements Program
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Abbreviation/
Indonesian term
Meaning/translation
Prov. Provincial
PSDA Pengelolaan Sumber Daya Air: Water Resources Management
PTAN PT Aquafarm Nusantara
PT Jasa Marga A state-controlled toll road operator that constructs and provides
toll road services
PTL-BPPT Pusat Teknologi Lingkungan: Center of Environmental Technology
under BPPT
PU and PUPR Kementerian Pekerjaan Umum Dan Perumahan Rakyat: Ministry
of Public Works and Housing
PusAir Pusat Penelitian dan Pengembangan Sumber Daya Air Kemen
(PUPR): Agency for Research and Development in Water
Resources, under MPW
Pusat Bendungan Pusat Bendungan – Kementerian Pekerjaan Umum dan
Perumahan Rakyat: Center of Dam/Reservoirs under The Ministry
of Public Works and Housing
RBO/RBMO River Basin Management Organization: Balai Wilayah
Sungai/Balai Besar Wilayah Sungai/Balai Pengelola SDA Prov
RBT River Basin Territory: Wilayah Sungai (WS)
Rencana Master Plan for River Basin Management (follow up of Pola)
RMCU Road Map Coordination Unit: Unit Koordinasi Road Map
RIBASIM River Basin Simulation Model, DSS for WR Planning and
Management: Model Simulasi Wilayah Sungai - Sistem
Pendukung Pengambilan Keputusan Rencana Pengelolaan SDA
RPJMN Rencana Pembangunan Jangka Menengah Nasional: National
Medium-Term Development Plan
Sawah Rice field
SDA Sumber Daya Air: Water Resources
Sekr Kabinet Sekretaris Kabinet: Cabinet Secretariat
SH Stakeholder: Pemangku Kepentingan
SKPD Satuan Kerja Perangkat Daerah: Regional Working Unit
SSK Strategi Sanitasi Kota: City Sanitation Strategy
Sumatera Utera North Sumatra
Suri Tani Pemuka A private fish company, part of JAPFA
SWOT Strengths, Weaknesses, Opportunities & Threats: Kekuatan
Kelemahan Kesempatan dan Ancaman
TA Technical Assistance
Tala lata ripe ripe Onshore fish ponds containing fish that are periodically released to
Lake Toba after reaching a certain age and size
TKPSDA Tim Koordinasi Pengelolaan Sumber Daya Air: Basin water
resources management council
TMK Tomok, a location of PT Aquafarm Nusantara
TN Total nitrogen
Toba Pulp Lestari Name of pulp company
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Abbreviation/
Indonesian term
Meaning/translation
Tokoh adat Local leader
Tokoh Masyarakat Public figure
ToR Terms of Reference: Kerangka Acuan Kerja
TP Total phosphorous
USDP Urban Sanitation Development Program: Program Pengembangan
Sanitasi Perkotaan
Unimed Universitas Negeri Medan
Univ. HKBP
Nomansen
Universitas HKBP Nomansen
URI University of Rhode Island
USU Univsitas Sumatera Utara: University of North Sumatra
WALHI Wahana Lingkungan Hidup Indonesia: Friends of the Earth
Indonesia
WISMP Water Resources and Irrigation Sector Management Program:
Program Pengelolaan Sektor Irigasi dan Sumber Daya Air
WLC World Lake Conference: Konferensi Danau se Dunia
WQ Water Quality: Kualitas Air
WQ Roadmap The development of the Roadmap for Improving Water Quality of
Lake Toba as a Tourism Destination
WRD Water Resources Development: Pengembangan Sumber Daya Air
WRM Water Resources Management: Pengelolaan Sumber Daya Air
WS Wilayah Sungai: River Basin Territory
WUA/P3A Perkumpulan Petani Pemakai Air: Water User Association
Yayasan Bina Sarana
Bakti
A foundation that produces organic vegetables
YPDT Yayasan Pencinta Danau Toba: Lake Toba Heritage Foundation
Exchange rate (November 3rd, 2017): IDR 13,495 = US$ 1 (xe.com)
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1 Introduction
1.1 Background
1.1.1 Water quality concerns at Lake Toba
Lake Toba belongs to the largest and deepest lakes in the world. Although the minimum
estimated residence time of the lake is around 80 years1 (Lukman, 2010), there is a concern
about the deterioration of water quality in Lake Toba. Numerous studies have been conducted,
with more recent assessments illustrating that Lake Toba is showing signs of environmental
degradation. Water quality at 22 monitoring locations has deteriorated from “good” in 1996 to
“insufficient” in 2012 with an alarmingly high level of suspended solids and chlorophyll
concentration (DLH-SU, 2017). Unprecedented algae blooms appeared from January to April
2016 for the first time since water quality monitoring started in approximately 1929. This was a
clear manifestation of the presence of higher phosphate and nitrogen levels.
The largest pollutant loads originate from aquaculture, followed by animal husbandry and
domestic waste (including tourism). Several institutes and universities have carried out pollutant
source analyses to understand the pollutant load pathways in Lake Toba and advise the
Government on its carrying capacity. Although these analyses differ somewhat, they all show
roughly the same picture, which has been summarized by the Provincial Environment
Department for North Sumatra (Dinas Lingkungan Hidup-Sumatra Utara, DLH-SU) in its advice
on carrying capacity given to the Minister of Environment and Forestry. The total phosphorous
emissions from aquaculture nearly doubled between 2012 and 2016 (from 1082 tons in 2012
to 2124 tons in 2016; DLH-SU, 2017). In 2016 this contribution was equivalent to the loads of
approximately 2.3 million people. In contrast, the domestic waste pollution load in 2016 of 197
tons, created by a population of 0.5 million people living in the catchment area, was equivalent
to roughly 0.2 million people (because part of the human waste stays behind on the land). This
domestic load has not changed over the years, with agricultural and other pollutant sources
having even smaller contributions.
Local and commercial aquaculture production started in the mid-1990s and has increased
rapidly over the past two decades. Aquaculture started in 1996 in Haranggaol Bay, located in
the northeastern part of Lake Toba, after several years of agricultural crop failures. Following
the example of successful aquaculture in the Jatiluhur reservoir, local Haranggaol farmers
decided to try aquaculture and were soon followed by many other local communities around
Lake Toba. Commercial operations started in 1998 with PT Aquafarm Nusantara (PTAN),
followed in 2012 by PT Suri Tani Pemuka.
The fish cages have been controversial since their inception because of environmental
concerns from local communities, local, provincial and national governments and
nongovernmental organizations (NGOs). These concerns have been aggravated by a series of
sudden and large-scale fish kills. Almost all fish production in Haranggaol Bay was wiped out
in 2004 because of a severe Koi Herpes virus infection. Following this, aquaculture was banned
for two years untill 2006. Another large fish kill occurred in Haranggaol Bay in May 4, 2016
(Danaparamita, 2016), followed by another in Silalahi village. Both fish kills are thought to have
1 Residence time is discussed in more detail in section 2.2.4 and annex C.1.
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been caused by overstocking of the cages. Local NGOs subsequently launched a series of
court cases against the licenses of commercial aquaculture companies operating on the lake.
The Government has issued several instructions in response to the deterioration of water
quality. The Minister of Environment and Forestry issued a letter (menlhk/ppkl/pkl.2/4/2017) on
April 03, 2017 to ask the Governor of North Sumatra to establish the status of Lake Toba as
class 1, oligotrophic (see Annex C.3), with a maximum fish production in floating cages of
10,000 tons per year. This letter was followed by two provincial government decrees issued by
the Governor of North Sumatra on the lake status (no. 188.44/209/KPTS/2017) and re-affirming
the carrying capacity of 10,000 tons of fish production per year for Lake Toba (no.
188.44/213/KPTS/2017).
Pollution from livestock, mainly individually owned, is another water quality concern.
Unmanaged manure partly percolates into the soil and the rest finds its way via surface runoff
and drainage channels into Lake Toba. The same holds true for domestic wastewater. Very
few residents around Lake Toba are connected to a sewer network. Many of the current urban
on-site sanitation facilities do not comply with the definition of a septic tank and are more like
pit latrines, which means that polluted water leaks into the groundwater that in turn drains into
the lake. At times of high precipitation or floods, many tanks overflow.
There are several catchment land use considerations that also have implications for the water
resources of Lake Toba. Deforestation and land conversion have only a limited effect on the
water quality but impact the water resources of Lake Toba’s catchment area. As of November
2017, only two undisturbed forest patches remain, including the upstream forest in the
Sibuatan/Silalahi forest in the north-west of the catchment and the forest patches in the south-
east, including the forest of Taman Eden. The biodiversity in both areas is rich and the upstream
Sibuatan/Silalahi forest is particularly important for the water resources of Lake Toba as it
covers the upstream catchment of a large part of the run-of-river power plant from the Renum
River to Lake Toba. Large parts of the upper catchment of the Renum River have been
converted over the past 10 years. This has resulted in a significant reduction of up to 60% of
the base flow in the Renum River. Both remaining forest patches have no conservation status
and are severely threatened by local encroachment and conversion to agroforestry and timber
production (BWS-S2, see also www.globalforestwatch.org/map).
1.1.2 Rationale for roadmap
The tourism sector in Indonesia is a promising growth sector that can provide inclusive and
sustainable opportunities for economic development. The archipelago is home to one of the
most biodiverse habitats in the world having a rich array of tourism endowments that form the
underlying attraction for visitors. Indonesia has expanded the promotion of its natural resources
by increasing the size of protected areas and attracting more online interest in nature-based
activities. Despite this, Indonesia’s tourism industry is not operating at a level consistent with
the quality and diversity of its natural and cultural endowments, with environmental
sustainability as a key risk factor for the sector (WEF, 2017).
Four key constraints contribute to Indonesia not fulfilling its tourism potential. These include: (i)
continued poor and quality of infrastructure and services for citizens, visitors and businesses;
(ii) limited tourism workforce skills and private-sector tourism services and facilities outside of
Bali; (iii) weak enabling environment for private investment and business entry; and (iv) poor
inter-ministry/agency, central-local and public-private coordination and weak implementation
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capabilities for tourism development in general, and for monitoring and preservation of natural
and cultural assets in particular.
Through the National Medium-Term Development Plan (Rencana Pembangunan Jangka
Menengah Nasional, RPJMN, 2014) 2015-2019, the Government has set several objectives to
increase the role of tourism in the Indonesian economy. In early 2016 President Joko (Jokowi)
Widodo urged his Cabinet to accelerate the development of ten priority tourism destinations,
including Lake Toba. Recognizing the importance of integrated and sustainable tourism
development, the government plans to prepare integrated tourism master plans for each of the
priority tourism destinations, which are intended to provide a strong framework for effective and
sustainable tourism development.
The Government has launched the Indonesia Tourism Development Priority Program. For the
implementation of the program, the Government has decided to sequence the development of
tourism destinations, starting with three priority destinations: Lombok in West Nusa Tenggara
province; Borobudur-Yogyakarta-Prambanan in Central Java province and the Special Region
of Yogyakarta; and Lake Toba in North Sumatra province. If developed effectively, these three
distinctively different and unique destinations are expected to increase their combined annual
foreign and domestic visitor expenditures from an estimated US$1.2 billion in 2015 to US$1.5
billion by 2021 and US$2.0 billion by 2026. Lake Toba can become a more attractive destination
for a wider variety of predominantly domestic and some foreign visitors, particularly short haul
weekenders from Singapore and Malaysia (HHTL, 2017) 2.
1.2 Objective and approach
The objective of the Roadmap for Improving Water Quality of Lake Toba as a Tourism
Destination is to provide an understanding of the key drivers leading to water quality issues
along with costed investment scenarios associated with specific investments aimed at reducing
nutrient loads into the lake. The roadmap is intended to inform preparation of an Integrated
Tourism Master Plan that will provide a framework for effective and sustainable tourism
development in and around Lake Toba.
Safeguarding the water quality of Lake Toba is considered critical to ensuring the best-case
tourism development projections. The development of the Roadmap for Improving Water
Quality of Lake Toba as a Tourism Destination (hereafter “WQ Roadmap”) will provide inputs
to the government planning and budgeting process and to the Integrated Tourism Master Plan
for the Lake Toba tourism destination.
The Roadmap for Improving Water Quality of Lake Toba Tourism Destination has been developed through a series
of deliverables (
Table 1.1) and consultations (Annex A.2). This final report builds on all previous deliverables.
2 As part of the Tourism Development Project preparation, upon the GoI’s request, the World Bank conducted Demand
Assessments, prepared by Horwath HTL (HHTL), covering for each of the destinations: (i) baseline supply and
demand of tourism services; (ii) investment analysis; (iii) future market demand analysis (future visitors and
investors); and (iv) investment needs (destination infrastructure, tourism infrastructure, skills, firm capabilities, and
legal and regulatory environment). The Lake Toba report is available at:
http://bpiw.pu.go.id/uploads/20170302_Lake_Toba_Market_and_Demand_Assessment.pdf
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Table 1.1, List of deliverables
Task Deliverables
1 1. Inception Report/Literature Review
2. Stakeholder Assessment/ Mapping
3. Legal, Institutional and Political Economy Assessment
2 4. Lake and Catchment Assessment
3 5. Recommendations for Integrated Lake Basin Management Plan
4 6. Stakeholder consultations: PowerPoint Presentations and Workshops
1-4 7. Draft Final Report
1.2.1 Stakeholder consultations
The development of the WQ Roadmap followed an iterative process of consultation meetings
with identified stakeholders, coupled with specific analyses and a series of reports. These
reports have been discussed with stakeholders, thus creating a deeper understanding of
stakeholder roles and the legislative and institutional settings. This iterative process of
stakeholder consultation has helped to clarify roles and responsibilities, some of which even
changed during the process.
Pre-identified stakeholders, together with the participants of the Reference Group (sub-section
1.2.2), served as a starting point for the first stakeholder mapping exercises. During subsequent
meetings, the stakeholders themselves contributed to improved understanding of their roles
and responsibilities in monitoring and managing the overall catchment area of Lake Toba.
These consultations helped to complete the inventory of existing legal and institutional
arrangements, and in identifying additional stakeholders, while at the same time facilitating
access to information and data.
In addition to consultation meetings, stakeholders have also been involved throughout the
process through field visits and individual meetings (Annex 0). In some cases, semi-structured
interviews were conducted. These interviews served as a source of information on relevant
issues around Lake Toba and to understand the legislative and institutional settings, as well as
the political economy of the region.
1.2.2 Reference Group
A Reference Group was established by the Coordinating Ministry of Maritime Affairs and the
Ministry of Public Works and Housing to provide feedback and guidance throughout the process
(Annex A). This Reference Group included key experts and managing organizations involved
in environmental monitoring and management of Lake Toba and was the main contact group
to guide and assist in preparation of the WQ Roadmap. The Reference Group helped to identify
the historical and present arrangement of water quality management at Lake Toba and ensured
a comprehensive approach that builds on existing information to provide a solid foundation to
inform the preparation of the WQ Roadmap.
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1.3 Overview
Most chapters (and some sections) start with a description of the approach. Details of the
various tools and theoretical frameworks are included as annexes.
Chapter 2 introduces Lake Toba and its surroundings, the hydrology and functioning of the
lake, and key factors of the lake’s water quality problems.
In Chapter 3, the legal and institutional arrangements related to water quality at Lake Toba are
discussed. First, specific standards and institutions for water quality monitoring are discussed,
followed by the legislation and institutional aspects of water quality management. The chapter
concludes with an identification of various gaps between relevant laws and regulations and
their implementation in practice.
Chapter 4 provides an overview of the stakeholder mapping, followed by a stakeholder
assessment. Subsequently, the findings on the legal and institutional environment and
stakeholders are summarized in an overall analysis of the governance strengths, weaknesses,
opportunities, and threats (i.e. SWOT) for water quality monitoring and management.
In Chapter 5 the key factors causing the present state of Lake Toba are analysed. This chapter
includes a point and non-point source analysis with the Sumatra Spatial Model.
Chapter 6 summarises the present state of the water quality in Lake Toba. The quality of the
available data sets is assessed and subsequently the data have been analysed. Physical and
chemical parameters are discussed, together with an overview of available information on
nutrients, and organic content. Subsequently the thermocline depth is identified as well as
horizontal mixing and trends.
In Chapter 7 the autonomous growth developments are combined with various investment
scenarios to calculate future growth trajectories of the trophic state of Lake Toba. This supports
the identification of initial opportunities for water quality management.
In Chapter 8 responses have been formulated around a water quality management plan.
Interventions to address the most important drivers of water quality (aquaculture, livestock and
domestic wastewater) are elaborated, together with an assessment of the impacts on nutrients.
Contributions from other sectors are discussed as well.
Chapter 9 outlines a proposed water monitoring plan for Lake Toba based on a range of
assumptions that lead to different scenarios.
Chapter 10 summarizes the findings, conclusions and recommendations made in the previous
chapters.
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2 Lake Toba as a Tourism Destination
2.1 Lake Toba and its surroundings
2.1.1 Topography
Lake (Danau) Toba is the largest lake in Indonesia and one of the largest and deepest lakes in
the world (Annex B.1). The lake is about 100 kilometres (62 miles) long, 30 kilometres (19 mi)
wide, and up to 505 metres (1,657 ft) deep, with a volume of 240 km3 (58 cu mi). It is a volcanic
lake formed in the old caldera of the Toba Volcanic Complex situated on the island of Sumatra
along the Barisan Mountain Range (Figure 2.1). To the West lies the Indian Ocean and to the
East the lowlands of North Sumatra stretch out to the Malacca Strait. Steep cliffs, formed by
the caldera, surround the lake at an elevation of 400-1,200m above the lake level. As the
surface water level of Lake Toba lies at approximately 900m above sea level, the steep slopes
and volcanoes around the lake reach up to 2,100m elevation.
Figure 2.1, Topography of the catchment area of Lake Toba.
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The island of Samosir has a tilted surface with a maximum elevation of approximately 1,600m
above sea level or about 700m above the water level in the lake along the northeast side of the
island.
Around the lake to the northwest several volcanoes dominate the landscape. To the south a
larger relative flat valley with an approximate elevation of 1,200m above sea level is dominated
by cultivated land. Clearly visible in Figure 2.1 is the narrow valley to the east where the lake
overflows and discharges into the Asahan River. Here the water level regulation works have
been constructed and further downstream various hydro dams have been constructed. The
surrounding area is flat with the shores only a few meters above the lake surface.
The catchment area of Lake Toba and the Asahan River lies completely in the province of North
Sumatra, with a total of seven kabupaten bordering the lake, and another one (Pakpak Barat)
included in the national strategic region (Annex B.2). The largest populations can be found in
the relative flat areas along the west side of Samosir Island, along the south-east shore of Lake
Toba in Toba Samosir and around Prapat in Simalungun. As a result, most villages (desa) can
be found in those areas.
The soil in the region is typical for weathered volcanic areas and varies between light clay and
loamy sand (B.3). The four main soil types vary from somewhat sensitive to highly sensitive to
erosion (Damage Control Directorate of Aquatic Ecosystems, 2017). The soil type determines
runoff rates in the model (section 6.1).
2.1.2 Climate
The precipitation regime in the region is typical for the humid tropics and is characterized by a
major wet season from August through November and a minor wet season from March to May.
The months in between are transition-months with varying precipitation, never below 50 mm
per month (Table B.2). The average yearly precipitation in the region during the period 2003-
2016 amounts to approximately 2,850mm/year, with significant differences in total precipitation
from year to year. The average temperature is 21.5 degrees Celcius in the period 2006-2016,
and the annual reference evaporation is 1,556 mm (Hargreaves and Allen, 2003; Zomer et al.,
2008). See Annex B.4 for more details on climate.
2.1.3 Land-use practises and spatial development
Samosir Island is largely cultivated with upland plantations. Towards the west shores various
crops are cultivated. To the north are grasslands for cattle. Most tourist accommodations can
be found along the eastern shore and on the peninsula of Tuktuk. Along the cliffs of the caldera
to the east and southeast plantations can be found, while further to the north crops are
cultivated. The area is famous for its coffee plantations. To the west cattle are raised, and there
is a large pig farm. Down the slopes to the Indian Ocean forests are present. In the relatively
flat valley to the south rice and other crops are grown (Figure 2.2). The lake itself is used for
aquaculture with floating fish ponds that can be found all over the lake from north to south
(section 2.1.4).
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Figure 2.2, Land-use in the Lake Toba Catchment area, based on the 2013 dataset from BIG (Badan Informasi
Geofisika). Source of satellite imagery for this and other maps: Esri, DigitalGlobe, GeoEye, Earthstar Geographics,
CNES/Airbus DS, USDA, USGA, AeroGRID, IGN, and the GIS User Community.
In the catchment area of Lake Toba, most of the population (91%) live in rural settlements. Less
than 10% live in urban areas that together occupy 4% of the land. Some 10% of the land is
used as sawah to grow rice, 11% is occupied by plantations and on 27% other agricultural
dryland crops are grown. Aproximately a fifth of the land is covered by forest and another fifth
by shrubs, grassland and other natural vegetation. The various types of land use, as applied to
the Sumatra Spatial Model, are listed for each of the compartments in Annex J.3.
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2.1.4 Economy
Lake Toba and its surroundings provide substantial economic benefits to local people and
commercial enterprises. The average Gross Regional Domestic Product of the 8 districts
around Lake Toba was IDR 8.3 trillion in 2016 (at constant prices of 2010), with an average
growth rate of 4.8% in 2015 (Table 2.2; see also section 7.2.1). The main contributors to the
districts’ economy are agriculture, forestry, and fishing (includes aquaculture as well as
fisheries), together providing the major livelihood for the communities. Table 2.1 presents a list
of commodities produced in the area.
Table 2.1, Main commodities around Lake Toba (Ministry of Public Works and Housing, 2016)
Sector Commodities Location
Food crops and horticulture
Rice, corn, sweet potato, potato, andaliman, orange
Dairi, Simalungun (Haranggao Horison), Samosir (Panguruan, Palipi), Toba Samosir (Porsea, Sigumpar, and others), Humbang Hasundutan (Dolok Sanggul)
Plantation Coffee, incense, sweet skin, clove, candlenut
Samosir, Pakpak Bharat, Humbang Hasundutan, Tapanuli Utara, Karo
Rubber, cocoa, palm oil, tea
Humbang Hasundutan, Simalungun
Aquaculture Fish (Nila, Emas, Mujair)
Farming Pig, chicken, cow, buffalo
Simalungun (Dolok Pardamean)
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Table 2.2, Gross regional domestic product of Toba regencies by sector, based district-level data from the Central Bureau of Statistics, North Sumatra (in million IDR, at constant
price level of 2010).
Karo % Pakpak Barat % Dairi % Samosir % Humbang Hasundutan% Tapanuli Utara % Toba Samosir % Simalungun %
A Agriculture, Forestry Fishing 7,123,559.75 57% 425,784.11 59% 2,617,659.46 46% 1,385,461.90 53% 1,654,889.35 46% 2,431,668.98 48% 1,620,067.80 34% 13,203,969.70 56%
B Mining and Quarrying 30,634.33 0% 288.75 0% 3,727.68 0% 16,417.50 1% 21,046.74 1% 3,762.95 0% 14,008.70 0% 53,954.10 0%
C Manufacturing 387,997.37 3% 1,336.18 0% 18,954.53 0% 14,277.80 1% 56,471.72 2% 101,727.74 2% 524,576.50 11% 2,529,290.10 11%
D Electricity and Gas 11,302.38 0% 1,755.86 0% 5,186.49 0% 1,941.90 0% 3,437.86 0% 5,583.12 0% 4,132.40 0% 19,760.80 0%
E
Water supply, Sewerage, Waste
Management and Remediation Activities 10,217.54 0% 469.50 0% 5,079.92 0% 1,302.60 0% 2,434.12 0% 5,364.68 0% 2,462.40 0% 18,668.60 0%
F Construction 813,954.62 7% 65,821.24 9% 735,019.30 13% 267,911.90 10% 482,624.12 13% 635,966.05 13% 613,835.80 13% 2,037,563.00 9%
G
Wholesale and Retail Trade, Repair of
Motor vehicles and Motorcycles 1,243,155.78 10% 75,475.15 11% 920,838.25 16% 293,781.40 11% 524,852.23 15% 624,827.69 12% 762,992.10 16% 3,194,169.30 14%
H Transportation and Storage 560,896.99 4% 14,499.05 2% 209,413.35 4% 79,487.50 3% 87,213.74 2% 237,197.57 5% 141,297.70 3% 358,667.70 2%
I
Accommodation and Food Service
Activities 305,208.80 2% 16,144.65 2% 173,332.88 3% 127,683.10 5% 114,912.67 3% 112,940.47 2% 139,284.70 3% 205,646.50 1%
J Information and Communication 115,780.93 1% 5,785.70 1% 64,814.89 1% 26,617.80 1% 41,097.12 1% 47,653.29 1% 62,422.00 1% 165,234.50 1%
K Financial and Insurance Activities 159,881.14 1% 6,170.97 1% 115,168.38 2% 24,182.90 1% 41,312.07 1% 79,909.16 2% 81,873.40 2% 229,737.60 1%
L Real Estate Activities 391,078.37 3% 10,675.70 1% 148,766.37 3% 54,336.30 2% 95,420.12 3% 109,492.78 2% 134,491.40 3% 203,716.00 1%
M,N Business Activities 23,210.94 0% 135.23 0% 3,495.11 0% 3,054.50 0% 4,602.02 0% 14,254.06 0% 39,592.70 1% 19,094.30 0%
O
Public Administration and Defense;
Compulsory Social Security 695,684.32 6% 81,059.91 11% 521,808.68 9% 299,786.40 11% 382,968.00 11% 522,284.68 10% 450,008.00 9% 924,458.50 4%
P Education 314,507.22 3% 9,406.44 1% 108,117.93 2% 23,948.70 1% 36,991.10 1% 90,934.77 2% 132,378.60 3% 237,003.70 1%
Q Human Health and Social Work Activities 150,793.34 1% 2,917.53 0% 35,973.86 1% 13,750.20 1% 22,370.10 1% 39,919.53 1% 39,119.80 1% 83,729.00 0%
R, S, T, UOther Services Activities 157,003.60 1% 165.20 0% 1,093.84 0% 1,825.20 0% 5,105.97 0% 6,707.34 0% 7,261.30 0% 23,306.30 0%
Gross Regional Domestic Product 12,494,867.43 100% 717,891.17 100% 5,688,450.93 100% 2,635,767.60 100% 3,577,749.06 100% 5,070,194.85 100% 4,769,805.46 100% 23,507,970.00 100%
Gross Regional Domestic Product of Toba Regencies at Constant Price of 2010 by Industrial Origin (million rupiahs and percentage), 2016
IndustryNo
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Aquaculture is an important economic activity at Lake Toba; floating fish farm ponds populate the lake (Figure 2.3 and Figure 5.1). The aquaculture industry in Lake Toba can be divided into two types:
1. Industrial scale aquaculture by two companies, PT Aquafarm Nusantara and PT Suri Tani Pemuka;
2. Small-scale local aquaculture financed by domestic investors and local fisherfolk themselves.
Together the two commercial companies employ about 4,000 workers and the full production is exported to Europe and the United States. Financial details of the companies are not available to the public. Small to medium scale aquaculture enterprises produce primarly for the local market and are typically owner-operated, providing employment for more than 5,000 people. According to the Directorate General of Aquaculture and Fisheries (Ditjen Perikanan Budidaya, October 2015) there were at least 23,000 floating fish cages (KJA) in 2014. It is estimated (personal communucation Harian Analisa, June 5, 2017) that this amount of KJA provides direct employment to about 11,500 people for an average income of approximately IDR 60 million (US$ 4,450) per person per year.
Figure 2.3, Floating fish farms on Lake Toba (Photo by Aria Danaparamita, 2016).
The fish production at Lake Toba is not systematically monitored and estimates vary between sources and years (Table 2.3). In 2014 the 23,000 KJA were estimated to producing about 96,000 tons of fish, almost all red tilapia (Ditjen Perikanan Budidaya, October 2015). In 2015 the production dropped to about 84,800 tons and for 2016 estimates range from 64,000 to 74,400 tons (Table 2.3).
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Table 2.3, Estimated fish production in aquaculture at Lake Toba (in tons per year).
Producer
Estimated
production
2014
Estimated
production
2015
Estimated
production
2016
Estimated
production
potential
PT Aquafarm
Nusantara
34,000 30,000 30,000-40,000
PT Suri Tani
Pemuka
20,800 4,000 55,000
Haranggoal Bay 30,000 40,000
30,000-50,000
Other smallholders 30,000-50,000
Total 96,000 84,8003 74,400 64,000-96,000
Source Ditjen
Perikanan
Budidaya,
2015
DLH-SU,
2017
Discussions with
stakeholders,
2017
Estimation
2008-2016
Local aquaculture started in Haranggaol Bay around 1996 after several years of
agricultural crop failures due to fungus infections and overexploitation of the soils. The
succesfull introduction of the fish cages in Haranggoal was soon followed by many other
local communities around Lake Toba. Over time, many smallholders experimented with
fish cages at various locations on Lake Toba. Some abandoned their cages within a few
months, others moved their cages around to find the best location, and some aquaculture
farmers successfully produced fish for local restaurants that serve national and
international tourists.
In 1998, PT Aquafarm Nusantara started operation, as part of a joint Swiss
Government/Republic of Indonesia Investment Agreement (BKPM). This initiative was one
of the first pioneering bi-lateral socio-economic and development projects within
Indonesia’s fisheries and aquaculture sector (personal communication with PT Aquafarm
Nusantara, 20174). Following a request by the local government to stimulate the local
economy and employment, PT Suri Tani Pemuka, a national company, started fish
production in 2012 (personal communication with PT Suri Tani Pemuka). The Demand Assessment suggests that in 2015, approximately 7,000 persons worked in the tourism industry. Based on its best-case scenario, it forecasts around 10,000 people employed in the industry in 2026, and 15,000 in 2041. By 2041, spending by visitors to Lake Toba is expected to rise to US$275 million in the best case, from an estimated US$75 million in 2015.5 As Lake Toba will remain predominantly a domestic tourism destination, the majority of this projected spending increase (over 60 percent) will come from relatively lower-spending domestic visitors. Incremental economic impacts from an estimated five-fold increase in foreign visitors will therefore be more limited, reflecting the low starting
3 At the request of the Reference Group, the 2015 production level of 84,800 tons of fish has been used in the
assessment of nutrient loads for 2015 and in baseline scenario A. There was no agreement about the
production level in 2016, but various stakeholders suggested that the local small scale aquaculture production
might be under-estimated. 4 Letter from I Wayan Mudana, Director of PT Aquafarm Nusantara, to Deltares dated July 28th, 2017. 5 HHTL 2017 and World Bank staff estimates.
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level (only 60,000 visitors in 2015). The Lake Toba Tourism Area Management Authority (BOPDT) indicates that many investors have shown an interest in the area around Lake Toba in recent years, mainly with the intention of building hotels (Ratman, 2016; Gumelar, 2017 and Kumparan, 2017). BOPDT expects that after finalisation of road infrastructure, airports and ports, which is expected in 2020, investors will start their development activities. According to the Demand Assessment, the level of private investment in accommodation and other tourism-linked activities is expected to rise from only US$1.5 million per annum in 2015 to over US$15 million by 2041.6
2.1.5 Batak culture7
The hidden wealth in Lake Toba is comprised of non-financial resources including local
skills, trust and know-how, knowledgeable resource persons, and care-based
relationships. Lake Toba is an integral part of Batak history, culture, and spirituality. The
ancestors of Batak people chose Lake Toba as their permanent site for settlement
centuries ago. It was here that their descendants developed into the five ethnic Batak
groups; namely the Angkola-Mandailing, Karo, Pakpak-Dairi, Simalungun and Toba. Until
today, Lake Toba is a unifying point for Batak people who inhabit the surrounding lake as
well as those who migrated to other places.
For traditional Batak people, Lake Toba is valuable and important. In the pre-historic era,
the Batak’ view relies on its surrounding natural and environmental condition. Previously
there were strong beliefs in myths, legends, and historical inheritance through stories
shared verbally (some of which persist until today). One myth of Lake Toba stated that
Lake Toba began with a woman’s sadness over her husband telling their daughter an
important secret from her past, that she was previously a fish. She told her daughter to run
uphill because a huge disaster was about to come. When her daughter left, she prayed.
Soon there was a big earthquake followed by non-stop pouring rain. The whole area then
got flooded and became Lake Toba. The woman turned into a fish again and the man
became the island of Samosir. As such, Lake Toba is considered sacred by Batak people,
and there is plenty of local wisdom associated with Lake Toba.
Traditionally there are certain (unwritten) rules on dealing with waste, fish and the forest,
which need to be respected. In the past, anyone who bathed in Lake Toba and wanted to
urinate must come out of the lake, because of the strong belief that everyone should
respect the Lake. No one dared to throw garbage into Lake Toba. Violation of local wisdom
would have resulted in sanctions from local chieftains. In terms of fisheries, some local
wisdom includes the presence of no-fishing-zones, fish capture quotas (only certain
amount of fish and fish of certain size may be captured), as well as management of tala-
lata ripe-ripe (onshore fish ponds containing fish that are periodically released into Lake
Toba after reaching a certain age and size). The local wisdom to respect Lake Toba was
also extended into the forests surrounding the lake. No one would carelessly cut down
trees in the forests around Lake Toba. This local wisdom is only shared verbally through
word of mouth and not documented in written rules or customary guidelines, making it
challenging to reach new residents around the lake. However, much local wisdom as such
is eroded lately due to the large number of migrants and a change in economic activities.
6 World Bank staff estimates. 7 This section is largely based on Sianipar, 2011.
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2.2 Catchment hydrology and functioning of Lake Toba
2.2.1 Catchment dimensions and water level
The total area of the Catchment (including the lake) is approximately: 3,813km2, of which
the lake surface accounts for more than 1,100 square kilometers. The area around the
lake is very steep and as a result the sub-catchments are generally small (Table 2.4). A
total of 19 rivers drain into the lake, subdivided into 153 sub-catchments (Figure 2.4). The
catchments together provide an estimated at 111 m3/S or 3.5 billion cubic meters to the
lake through inflow.
Table 2.4, Lake Toba sub-catchment dimensions (Source: PU 4/2016)
Sub-catchment Size
Lake Toba 1,130km2
Samosir Island 653km2
Outside lake 2,030km2
Total 3,813km2
In addition to natural inflows from the catchment area into Lake Toba, an inter-basin
transfer from the Renun River was constructed in 1993 to augment water for the Renun
Hydropower Plant (PLTA). This tunnel diverts approximately 8-9m3/s on average and 20-
21m3/s during peak power supply (04:00-08:00hrs and 16:00-23:00hrs) (Figure B.5).
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Figure 2.4, The catchment and sub-catchment areas of Lake Toba.
The only outflow from Lake Toba is in the south-east, and drains into the Asahan River
with water flowing towards the Strait of Melacca. In this river, a regulating dam and several
hydro dams have been constructed. The objective of the regulating dam at Siruar is to
manage Toba outflow to the Asahan River in such a way that the Toba Lake water levels
are within the range required for various uses on site and downstream. Thus, the water
level is kept between 905.25m and 902.50m above sea level. This is done with a release
between 90 and 140m3/s to the downstream Asahan River. Annex B.5 shows the releases
as well as the resulting end-of-month Toba Lake water levels. The water balance for Lake
Toba is summarized in Table 2.5. For the model, an average flow of 110m3/s has been
selected; see Table 7.2 and Table 7.3 that also show the flows between compartments.
Table 2.5, Simplified water balance for Lake Toba
Total for lake
Variables Rate In (Mm3/year) Out (Mm3/year)
Precipitation 2850
mm/year
3,203.4
Evaporation 1556
mm/year
1,748.9
Inflow 56 m3/s 1,762.2
Inter Basin Exchange Renun 8 m3/s 252.3
Outflow (110 m3/s) 3,469.0
Total 5,217.9 5,217.9
2.2.2 Catchment erosion
The conversion of forests surrounding Lake Toba into other types of land use, coupled
with illegal logging and land and forest fires, have contributed to the deterioration in Lake
Toba’s water quality. This is because of the combination of major and minor nutrients,
trace elements, and natural organic compounds released by the erosion of Toba
watersheds that together stimulate algal growth.
The high rate of erosion in the catchment of Lake Toba is characterized by the abundance
of land parcels with very thin soil layers or areas with exposed bedrock, especially in hilly
areas with steep slopes. Approximately 27 percent of the catchment area is composed of
open land, grasses, and shrubs (KLHK, 2017). When the topsoil becomes thin due to
erosion, it is difficult to develop natural forests again. This problem is exacerbated by the
facts that the topography of the catchment is quite hilly with steep slopes and that the soil
types are sensitive to erosion (KLHK, 2017). According to the Minister of Environment and
Forestry, up to 21% of Lake Toba catchment areas have been identified as critical land
(Times Indonesia, 2016). Almost every year forest and land fires occurr, burning scrub and
trees, causing loss of cover vegetation and increasing vulnerability to erosion. Continued
erosion further complicates the growth of new vegetation as the soil layer gets thinner.
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The interactive map of Global Forest Watch (2016) indicates that there has been some
moderate tree cover gain over the past 12 years around Lake Toba. This may be the result
of multiple programs and projects on reforestation and rehabilitation that have been carried
out by different stakeholders. Tree cover loss is also recorded, primarily within and near
the concession areas of PT Toba Pulp Lestari near Parapat and to the west of Lake Toba.
2.2.3 Biogeochemical processes in Lake Toba
In deep lakes, such as Lake Toba, algal growth is typically limited by light. This is because
of the large epilimnion depth over which the algae are being mixed (see Annex C.2 for the
theoretical background on biochemical processes). The peak biomass concentration of
the algal bloom is determined by the availability of nutrients. Nutrient addition from run-off
(land activities) and direct input from aquaculture, can lead to higher nutrient
concentrations in the upper layer above the thermocline. This may thus lead to higher algal
biomass in the event of an algal bloom. Therefore, the hydrothermal stability of Lake Toba
is of major importance. Hydrothermal stratification is a key aspect which is further
discussed in sections 6.6 and 6.8.
2.2.4 Residence time and recovery time of Lake Toba
Residence time, or turnover time, is the theoretical time required to refresh a water body
(Annex C.1). The residence time is calculated by dividing the lake volume by the outflow.
For Lake Toba the residence time is approximately 80 years, because of the lake’s large
water body and the relative small outflow. This means that if Lake Toba becomes polluted
with a soluble toxic element, and the source of the pollution is eliminated, it will take more
than 80 years before the polluted water has left the reservoir and is replace with non-
polluted water. Consequently, changes in water quality may be irreversible as a result of
the long residence time of the water in the lake.
2.2.5 Stratification
Lake Toba is a stratified lake, which means that it is not fully mixed but consists of various
water layers that are characterized by different temperatures and oxygen concentrations.
Stratification is clearly visible in the temperature and oxygen profiles at various locations
in Lake Toba in 1992 (Figure 2.5). The profiles show temperature and oxygen ranges that
fall within the generalized temperature and oxygen ranges as reported for mayor
Indonesian lakes deeper than 100m (Lehmusluoto and Machbub, 1997). The mixing layers
(thermoclines) in these temperature profiles seem fairly large, but slightly more stratified
in the Northern basin.
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Figure 2.5, Thermal profiles of the north and south basins of Lake Toba, indicated in red (Source:
Lehmusluoto and Machbub, 1997).
Lake Toba can be classified as ‘warm monomictic’ based on the generalised relationship
between mean depth, surface area and lake stratification type, (see Figure 2.6; Lewis,
2000. Warm monomictic lakes are lakes that never freeze, and are thermally stratified
throughout much of the year. The density difference between the warm surface waters,
the epilimnion, and the cooler bottom waters, the hypolimnion, restrict lake water mixing
during much of the year. The period of stratification in tropical lakes is typically long, but
the stability of the middle (thermocline) layer is relatively low, and is influenced by wind
and rain events that cause partial mixing (Lewis, 2000). More on assessment of the
thermocline depth in section 6.6.
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Figure 2.6, Generalised relationship between mean depth, surface area and mixing patterns in tropical lakes
(adapted from Lewis, 2000).
2.2.6 Horizontal lake circulation and zonation
Water mixing in Lake Toba is not homogenous and the lake cannot be considered a
homogenous water body. This means that nutrient loading in the north does not
immediately affect nutrient concentrations in the southern part of the lake. Horizontal
circulation patterns are an unknown variable, influenced by flow velocities. Flow velocities
in Lake Toba have been modelled by the Indonesian Institute of Sciences, Lembaga Ilmu
Pengetahuan Indonesia (LIPI) under the influence of real occurring prevailing wind
directions (Figure 2.7; Rustini et al., 2014). The flow velocities are mostly below 0.2m/s,
which is normal for lakes. The resulting horizontal circulation patterns are shown in Figure
2.8. Both examples show cells of circulating water and no clear direction of flow. Northern
and southern parts do not mix intensively. However, current water quality estimates are
based on complete vertical mixing and complete horizontal mixing.
Lake divisions were proposed to explore the implications for water quality dynamics. These
are based on topography, bathymetry, circulation flow directions and velocities (Figure
2.8), and sampling sites (section 3.3) following the advice of Oakley (2015). Three options
were defined for the purposes of the analysis: 1) one compartment, looking at the lake as
a whole; 2) two compartments; and 3) four compartments (Figure 2.9). Future models
could consider additional compartments.
Danau TobaLake Toba
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Figure 2.7, Flow velocities as calculated by modelling Lake Toba (source: Rustini et al., 2014). Orange
indicates 0-0.20 m/s, yellow 0.20-0.40m/s, light green 0.40-0.60 m/s and dark green 0.60-1.00 m/s.
Clearly the outflow of the lake in the south-eastern part is seen, where flow velocities are locally
higher.
Figure 2.8, The circulation pattern in the northern (left) and southern (right) part of Lake Toba as modelled by
LIPI (Rustini et al., 2014). The image shows ‘cells’ of circulating water. The length of the arrows
indicates flow velocity.
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1 compartment – the lake as a whole
2 compartments: north and south lake
4 compartments: 1 northern and 3 southern lakes
Figure 2.9, Possible zonation options for Lake Toba (base maps adapted from Chesner, 2012).Indicative
flows for the whole lake in billion m3/year.
N
S1
S3
S2
N
S
1compartmentWholelake
2compartmentsNorthandSouthlake
4compartments1Northand3Southlake
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2.3 Key factors of Lake Toba water quality problems
The key water quality factors for Lake Toba are assessed following the Driver, Pressure,
State, Impact, Response (DPSIR) concept (Borja et al., 2006, Annex D). On the catchment
level, the drivers, land use changes (being pressures and state) and impacts are shown in
Figure 2.10. Together, these forecast the autonomous growth and investment scenarios
in the model. The main drivers of urbanization are population growth, household size
reduction, economic growth and job growth. The resulting urban area growth can have
serious impacts on the water resources.
Figure 2.10, Drivers of land use change and associated impacts.
In Figure 2.11 and Figure 2.12 an overview is given of all drivers and pressures linked to state and impacts as mentioned in the mechanism of eutrophication as described by Chapman (1996). Also the emission routes to the lake are shown in the links between drivers, pressures and “nutrient loading”.
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Figure 2.11, Schematic overview of drivers, pressures, state and impacts (part of DPSIR) of nutrient related water quality at Lake Toba (left part).
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Figure 2.12, Schematic overview of drivers, pressures, state and impacts (part of DPSIR) of nutrient related water quality at Lake Toba (right part). Inset: Overview of DPSIR.
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The DPSIR scheme identifies point and non-point sources that influence the Lake Toba
environment; these sources are quantified in Chapters 5 and 6. Table 2.6 shows the links
between drivers, pressures, environmental state and impacts for Lake Toba, with a focus on
possible water quality issues.
Table 2.6, Drivers, Pressures, State, Impact and Responses (DPSIR) for water quality in Lake Toba.
Driver Pressure State Impact Response
Agriculture Livestock: manure
management
Nutrient loading by P,
N runoff
Alg
al b
loo
m, T
urb
id w
ater
, Oxy
gen
dep
leti
on
, gas
eru
pti
on
s (p
oss
ibili
ty u
nkn
ow
n)
lead
ing
to p
oss
ible
eff
ects
: -
Dec
reas
e in
sw
imm
ing
wat
er q
ual
ity,
-
Low
er a
qu
atic
bio
div
ers
ity,
sh
ift
in k
ind
s o
f sp
ecie
s,
- Lo
ss o
f n
ativ
e fi
sh a
nd
fis
h p
rod
uct
ion
cap
acit
y,
- Lo
wer
aes
thet
ic v
alu
e.
Measures to reduce livestock runoff
(unknown)
Agriculture Paddy: fertilizer use Fertilizer management program;
WWT irrigation
Agriculture Plantation: fertilizer use Fertilizer management program;
WWT irrigation
Agriculture Other agriculture: fertilizer
use
Fertilizer management program
Aquaculture Industrial scale
aquaculture: feed, fish
faeces, dead fish Nutrient loading by
direct input of P, N
through feed
Limit tonnage produce, improve
Feed Conversion Ratio
Aquaculture Local aquaculture: feed, fish
faeces, dead fish
Limit tonnage produce, improve
Feed Conversion Ratio
Domestic Urban population: organic
waste, faeces, waste water Nutrient loading by
river discharges of P,
N per person day
Centralised Waste Water Treatment
(Domestic)
Domestic Rural population: organic
waste, faeces, waste water
Septic Tank
Forestry Plantation: fertilizer use,
erosion Nutrient loading by
runoff and
subsequent discharge
from rivers of
(natural) emission of
P, N
Waste Water Treatment (Irrigation)
Land cover
(other)
Grass/other none
Land cover
(other)
Shrub none
Land cover
(other)
Forest none
Tourism Tourists in large hotels
Nutrient loading by
emission of P, N per
tourists day
Waste Water Treatment (Hotel)
Tourism Tourists in small hotels and
homes
Centralised Waste Water Treatment
(Domestic)
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3 Legal and Institutional Environment
3.1 Approach
A stepwise approach identified legal and institutional aspects relevant to the monitoring and
management of water quality in Lake Toba (adapted from Fritz et al. 2009, 2014). First the
specific problem is diagnosed, identifying any dysfunctional legal and institutional patterns. This
is followed by an analysis to determine why the observed patterns are present. In the response
chapter (chapter 8) ways forward are then identified. The legal and institutional assessment is
closely linked to the stakeholder assessment (see chapter 4).
Various laws, government regulations, presidential regulations, presidential decrees,
ministerial regulations, ministerial decrees, and governor decrees address water quality in
Indonesia. A list of all relevant laws is presented in Annex F. In most of these, water quality
monitoring and management are considered in unison and a distinction between these two
cannot easily be made in the Indonesian Water Resources Law of 2004. However, for the WQ
Roadmap the two dimensions of water quality monitoring and management have operational
importance. Hence, where possible and relevant these are discussed separately. An overview
of concerns, plans, efforts, and legal and institutional settings is maintained and provided by
the Lake Rescue Initiative (Germadan) for Lake Toba (KLHK, 2017). This has been an
important source of information for this chapter.
3.2 Standards for monitoring
Several standards for water quality apply to Lake Toba and provide legal guidance for
monitoring. In addition to national government legislation in Indonesia (Figure 3.1), voluntary
international standards for aquaculture are applied by commercial ventures.
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Figure 3.1, Overview of official water quality standards for Lake Toba over time, as part of the legal framework in Indonesia.
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3.2.1 Oligotrophic status and class 1 standard
Government Regulation No.82 of 2001 sets the water standard for drinking water in Indonesia.
Following that regulation, the governor of North Sumatra in 2009 classified Lake Toba as Class
1 Raw Water for drinking water through the Governor’s Regulation No.1 Year 2009. The
Governor’s regulation also set the water trophic status of Lake Toba as Oligotrophic. Although
this regulation provides a clear standard for Lake Toba’s water, the water quality of Lake Toba
has deteriorated to mesotrophic for several variables in most compartments (see section 6.10).
Discussion on Toba’s water standards re-emerged in 2017. After several years of intensive
investigation by institutes like LIPI, Environmental Provincial Agency (DLH-SU), PusAir and
several universities, the target water quality standards and required trophic state of lake Toba
were confirmed by the Minister of Environment and Forestry, in her letter on April 3, 2017 to
the Governor of North Sumatra8. The letter indicated that:
• The water quality of Lake Toba should meet class I (raw water for drinking water), as per
the standards set by the Government in 2001 (82/2001), and the classification of Lake Toba
by the Governor in 2009 (1/2009, chapter 5).
• The trophic status of Lake Toba is defined as oligotrophic in the Governor’s Regulation No.1 Year 2009.
• The maximum carrying capacity for fish cultivation in Lake Toba is set at 10,000 (ten thousand) tons of fish per year from fish cages (Keramba Jaring Apung, KJA).
The letter of the Minister of Environment and Forestry was a confirmation of the status of Lake
Toba as well as an instruction on the carrying capacity. This instruction was based on the
various studies mentioned above. The letter was followed by the Governor of North Sumatra’s
Decrees 188.44/209/KPTS/2017 and 188.44/213/KPTS/2017. These decrees made the
instructions on the pollution load and carrying capacity of Lake Toba legally binding. The
decrees also served to instruct the sub-national government officials and district heads on the
water quality maintenance of Lake Toba. The decrees confirmed the Minister’s letter and
passed it on to direct guidance for keeping the nutrient levels near zero. This means that source
pollution control became one of the key parts of the environmental management of Lake Toba.
DLH-SU confirmed this directive with the Governor, and provincial regulations followed the
recommendations by the Minister. However, regarding the limitation of aquaculture, the Ministry
of Marine Affairs and Fisheries would like to communicate further to determine the maximum
production level and look for alternative incomes for fish farmers. No consistent data are
available on the exact fish production over the years, especially because the total production
of local small and medium scale aquaculture is not monitored. Various stakeholders suggested
that the local small-scale aquaculture production might be underestimated. Numbers for total
production vary between 64,000 and 96,000 tons of fish produced per year between 2014 and
2016 (Table 2.3). As there appeared to be consensus9 about the 2015 production level of
84,800 tons of fish, that value has been used in this study. The Ministry indicates that some
time should be given to the investors and proposes a five-year implementation period, ensuring
compliance with the provincial regulations. The Ministry is still in the process of collecting
responses of other authorities mentioned in the letter (i.e. the eight districts around Toba).
8 MENLHK/PPKL/PKL.2/4/2017. The letter was copied to Coordinating Ministry of Maritime Affairs, Ministry of Public
Works and Housing, Ministry of Marine Affairs and Fisheries, and the eight districts surrounding Toba. 9 Among the members of the Reference Group.
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Although the letter of the Minister and the Governor’s Decrees allow for immediate further
action, and although the letter already included the eight districts, the letter was not addressed
to the Minister of Home Affairs. Based on the lessons learned from the past, the involvement
of the Minister of Home Affairs is crucial to provide clear direction to the different districts for
implementation. The roles of these and other governmental and non-governmental
stakeholders are elaborated in the next sections and in chapter 0.
3.2.2 Aquaculture Stewardship Council (ASC) Standards
On top of the oligotrophic status and Class 1 Standard set in the Governor’s Decrees,
commercial aquaculture in Lake Toba abides, voluntarily, by the regulations and principles of
the Aquaculture Stewardship Council (ASC)10. The two commercial aquaculture farms at Lake
Toba, PT Aquafarm Nusantara (PTAN) and PT Suri Tani Pemuka have been certified by the
ASC. This certificate indicates that all fish production activities have a minimal environmental
and social impact. ASC principles focus on: compliance with national and local regulations,
conservation of local habitat and biodiversity, preservation of water quality and water resources,
social responsibility and human welfare.
According to the most recent publication of the ASC Tilapia Standard, V1.1 2017, diurnal
dissolved oxygen fluctuation was selected as a practical parameter for limiting the effects of
eutrophication on a particular water body. However, it was considered necessary to go beyond
an oxygen criterion to protect waters that have low nutrient concentrations and where the
diurnal dissolved oxygen fluctuations are minimal; i.e., oligotrophic systems. To avoid the
excessive loading of nutrient-poor systems, a limit on the total phosphorus concentration in
these oligotrophic receiving waters has been imposed. Additionally, a limit on the concentration
of chlorophyll α has been established to restrain the productivity in these water bodies.
Water quality requirements for ASC with respect to eutrophication:
- The relative change in diurnal dissolved oxygen of receiving waters relative to dissolved
oxygen at saturation for the water’s specific salinity and temperature ≤ 65%
Additional water quality requirements for ASC with respect to oligotrophic receiving waters:
- Maximum diurnal change in percentage of dissolved oxygen is 65%. - Maximum Secchi disk visibility limit is 10 meters. - If Secchi disk visibility is equal to or less than 5 meters then:
o Maximum total phosphorus concentration limit in water is ≤ 20 μg/l o Maximum Chlorophyll α concentration in water is ≤ 4 μg/l
- Maximum amount of phosphorus added to culture system per metric ton of annually produced fish is ≤ 27 kg.
- Maximum amount of phosphorus released from culture system per metric ton of annually produced fish is ≤ 20 kg.
The standards prescribe that measurements shall be taken at the Receiving Water Farm Afar
(RWFA) sampling station. The RWFA is a point where the farm effluent has an influence in the
10 The Aquaculture Stewardship Council is an independent international non-profit organisation that manages the world’s
leading certification and labelling program for responsible aquaculture.
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receiving waters but is not in the immediate outfall/mixing zone. This location would be
downstream in a river, or down the prevailing current pattern in a lake, reservoir or estuary.
Note that, although additional requirements are set for oligotrophic waters, a quantitative
definition of the term ‘oligotrophic’ is not provided in the ASC Tilapia Standard. The
requirements above do imply that water bodies with an average annual Secchi disk visibility at
or above 10 meters are not permitted as receiving waters under the ASC Tilapia Standard
because of their ecological uniqueness and rarity. The implications of this for Lake Toba are
discussed in sections 6.3.3, 6.9.1, 6.9.2, and 8.2.1.3.
3.3 Institutional arrangements for monitoring
Several institutions conduct water quality monitoring activities in Lake Toba. These institutions include a range of public and private institutions with skilled personnel and equipment to monitor the water quality of Lake Toba. Of all the monitoring efforts done, the most important aspect in quality of water sample analysis is the consistency of the laboratory chosen. This allows for a more objective and consistent comparison between samples over time. The four major water quality monitoring institutions are described below.
3.3.1 Provincial Environment Department – North Sumatra (DLH-SU)
The Provincial Environment Department (till 2016 known as BLH, Badan Lingkungan Hidup, the Provinvial Environment Agency) of North Sumatra (DLH-SU) is tasked with the general monitoring role of the lake’s water and provides a signal function. The agency has 22 monitoring locations distributed over the whole lake that have been measured over a period of 10 years with a frequency of once or twice per year.
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Figure 3.2 shows the location of the 22 sampling points in 2016. The choice of monitoring locations is based on the coverage of the larger bays, inhabited coastline and aquaculture locations along the coastline to capture pollutant loads and effects. Overall, the frequency is aimed at monitoring long term trends in lake status (over decades), not short-term changes. DLH-SU focusses on parameters near the shore, as DLH-SU consider these near-shore monitoring points to be connected to local pollutant sources.
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Figure 3.2, Overview of the 22 locations sampled by BLH-SU (currently DLH-SU) in 2016, based on data from DLH-
SU, 2016.
3.3.2 Indonesian Institute of Sciences (LIPI)
As a research institute, LIPI seeks to understand the Lake Toba System for exploratory and scientific purposes. The institute has conducted various measurement campaigns across a range of locations and parameters. It has data of measurements starting in 2009 in which the analysis was carried out in LIPI’s own laboratory. The particular spatial distribution of sampling locations was selected with the aim to cover the deeper central parts of the whole lake to collect useful depth profiles (Figure 3.3). LIPI focuses on characterizing the lake itself by selecting only mid-lake monitoring points. LIPI is developing a 3D hydro-dynamic model for the lake in which the horizontal and vertical circulation is modelled dynamically. Such a 3D model of the lake circulation is primarily for future use, when more data are available to operate and verify the model.
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Figure 3.3, Overview of the 12 stations sampled by LIPI in 2009, based on information from LIPI (2009).
3.3.3 River Basin Operator (PJT1)
Perusahaan Umum Jasa Tirta (PJT) is the national corporation for basin management. PJT1
is the corporation responsible for the Brantas, Bengawan Solo, Toba Asahan and other river
basins. PJT2 is responsible for the Citarum River basin. In Presidential Decree No. 2/2014
(section 3.4.2) the President appointed PJT1 for operational lake management, with a role and
mandate on management of surface water sources in Toba-Asahan. PJT1 collects fees for the
management and monitoring of the lake. PJT1 is planning to build its own monitoring laboratory
near Parapat, North Sumatra to support its lake management efforts. PJT 1 has recently started
monitoring water quality (Figure 3.4; Annex G).
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Figure 3.4, Overview of the sampling locations of PJT1, based on information from PJT 1 in 2017.
3.3.4 PT Aquafarm Nusantara (PTAN)
Aside from monitoring efforts by government institutions, private stakeholders are interested in
water quality data of the lake and have their own monitoring efforts. For example, PT Aquafarm
Nusantara (PTAN), one of the two large aquaculture companies11, needs data for its
Aquaculture Standard Certification (ASC). It therefore needs to understand the effect of
aquaculture activities overtime on the lake system, especially on areas where the activities take
place. They have 4 monitoring locations, three of which are located at the center of fish farm
areas: Panahatan, Tomok and Pangambatan (Figure 3.5). The fourth station is located in the
centre of the lake (CL), and provides a reference as it is assumed not to be affected by the fish
farms. These data have been measured over a period of 10 years with a monthly frequency. At
one of the locations a temperature and oxygen profile is available over the full period. PTAN
uses on-site labs and these are periodically quality-checked by Wageningen University and
Research in the Netherlands. PTAN is focusing on their aquaculture farms and has one
reference point.
11 The other company out-sources water quality monitoring.
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Figure 3.5, Overview of Lake Toba catchment (top) and area with the 4 sites sampled by PTAN (bottom).
Panahatan (PTH), Tomok (TMK) and Pangambatan (NGB) are aquaculture locations (TMK was closed in
2008), CL is a control location in the middle of the lake. The color coding has been consistently applied in all
PTAN graphs.
3.4 Legal arrangements for water quality management
Various laws and institutional arrangements are in place for water quality management at Lake
Toba, at provincial, national, and international levels. The central level provides guidance,
evaluation and monitoring. Each ministry has its own scope, with implementation at the
provincial or district level. The processes that lead to the development of laws and regulations
sometimes overlap, as can be seen in the overview over time in Figure 3.6.
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Figure 3.6, Overview of legislation and formal institutional arrangements on Lake Toba over time. Note that the first fish cages appeared at Lake Toba in 1996.
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3.4.1 Provincial setting
Multiple efforts have been undertaken by different levels of government to protect and
safeguard Lake Toba. At the provincial level, in 1990, the Governor of North Sumatra issued a
Regional Plan with special attention to the protection and management of Lake Toba. In 2003,
through Provincial Regulation No. 7/2003, a provincial spatial plan was developed. Based on
this spatial plan, the Asahan Authority and the North Sumatra Provincial Government
developed the Lake Toba Ecosystem Management Plan (LTEMP) in 2004, which later formed
the basis for the Germadan developed by the Ministry of Environment (BKPEKDT, 2005;
Soeprobowati, 2015).
Law No UU 23/2014 regarding Sub-National Governance is a national level law, giving authority
to the provinvial levels, making them responsible for various basic services. This
decentralization law covers various sectors including Education, Health, Drinking Water,
Drainage, Wastewater, and Solid Waste, to name a few. One of the regulations includes the
Minimum Service Standards, in which the formal document is still a working draft. Based on
this law, district heads (heads of local government) are obliged to reach their target as their key
performance indicator, especially for drinking water and wastewater.
3.4.2 National setting
The LTEMP was one of the key inputs in 2009 for the 1st National Conference of Lakes in
Indonesia, which was organized to save and manage not only Lake Toba but also other
degrading lake ecosystems around Indonesia. The Conference resulted in the 2009 Bali Lake
Agreement, whose aim is to maintain, preserve and restore lakes’ functions based on balanced
ecosystem principles as well as environmental carrying capacity. This would be done through:
1. Management of lake ecosystems,
2. Utilization of lake water resources,
3. Development of lake monitoring, evaluation and information systems,
4. Formulation of adaptation and mitigation steps to prepare for climate change,
5. Strengthening of institutional capacity and coordination,
6. Enhancement of community roles and participation,
7. Sustainable financing.
The Agreement was supported by eight ministries (Environment, Home Affairs, Public Works,
Agriculture, Energy and Mineral Resources, Marine and Fisheries, Culture and Tourism, and
Forestry) and one agency (Agency for the Assessment and Application of Technology, BPPT).
While the ministries formally have a “willingness to collaborate with all parties”; the Agreement
was not legally binding. It included a first set of 15 priority lakes, including Lake Toba. In 2014,
all institutional and legal arrangements were nearly completed for full scale implementation of
the Agreement. The Ministry of Public Works and Housing prepared the draft Government Lake
Regulation (without a number assigned). However, in February 2015 the Water Resources Law
7/2004 was cancelled by the Constitutional Court (order No. 85/PUU-XI/2013). Lacking a legal
basis, the process came to a standstill and the Bali Lake Agreement (including the Germadan)
was not implemented. Consequently, the Lake Toba Ecosystem Management Plan (BKPEKDT,
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2005) was not implemented either, as it did not provide any legally binding implications for the
district and local levels. As a result, the Ministry of Home Affairs never adopted the plan as a
priority program.
In 2008, through the Government Spatial Planning Regulation No. 26/2008, Lake Toba area was named a National Strategic Region (NSR). Presidential Decree No. 2/2014 appointed PJT1 for operational lake management, with a specific role and mandate on management of surface water sources in Toba-Asahan. Both NSR and PJT1 are referred to as “initiative”: NSR because Lake Toba became a strategic tourism area. Also, PJT1, unlike BWS Sumatera II, is profit-oriented and can collect fees. The Decree was followed by two Presidential Regulations: Presidential Regulation No. 81/2014 and Presidential Regulation No. 49/2016. Through Presidential Regulation No. 81/2014 the NSR status was further strengthened and PJT1 was assigned the tasks to:
• manage the catchment area to maintain the sustainability of water resources and minimize
erosion to prevent sedimentation;
• maintain the water quality and manage the land and water contamination; and
• protect biodiversity and a sustainable biological production for local communities.
This Presidential Regulation also gives guidance on fisheries practices (Clause 8 (5) a, b, c, d),
in which aquaculture activities should occur at least 10 meters from the shore. The permits for
aquaculture activities issued by the districts also require the fish cages to be located only in
zones where the water depth is more than 100 meters. Based on this Presidential Regulation,
the Provincial Spatial Plan for North Sumatra (RTRW) has been formulated and was passed
as Provincial Regulation No. 2/2017 on January 13th, 2017 (Bisnis.com, 2017). PT Suri Tani
Pemuka tried to comply and moved the fish cages further onto the lake. However, as the cages
could not withstand the larger wave action further away from the shore, the cages were moved
back. No other efforts to comply have been observed.
In 2015, partly stimulated by the upcoming International World Lake Conference (WLC, Bali
2016) and also to address a large concern regarding the rapid degradation of many lakes in
Indonesia, the Ministry of Environment and Forestry started the Lake Rescue Initiative (or
Germadan) as a follow-up to restart the 2009 Bali Lake Agreement. At the Bali 2016 World
Lake Conference, a priority Lake Program was initiated whereby:
• Ministry of Public Works and Housing made IDR 330 billion (US$ 25 million) available for
the restoration and safeguarding of seven priority lakes, including Lake Toba;
• Ministry of Environment and Forestry issued Germadan Initiative as part of RPJMN 2015-
2019. This encompassed 15 priority lakes, including Lake Toba. The Germadan Initiative
was sent to the Coordinating Ministry for Economic Affairs for implementation.
Germadan Toba attempts to review all the regulations related to Lake Toba and analysed the
gaps in the overall management of Lake Toba, including its surroundings. It offers a set of
recommendations and timeline for different aspects of Lake Toba Management. In terms of
implementation of the recommended actions, so far, the Ministry of Environment and Forestry,
together with the Provincial Forest Service, have implemented a reforestation program. In this
program, members of the community are invited to manage 10 hectares of forest, for which
they get permission to plant 1 hectare with whatever trees they want. Nevertheless, the
stakeholders expressed fears that the Germadan is at risk of becoming yet another review or
planning document with little impact or no implementation because it does not legally bind the
stakeholders mentioned in the document to conduct certain actions.
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Indonesia’s Medium Term National Development Plan for 2015-2019 contains numerous
targets to be achieved by 2019. Few of them include the national target to achieve universal
water and sanitation access. This means 100 percent coverage for drinking water with 15 litres
per capita per day, sanitation, and rehabilitation of up to 5.5 million hectares of critical lands.
Priority is given to improvement of the urban solid waste situation for the period 2015-2019.
These targets act as guidance for management efforts on Lake Toba’s waters as well.
At the national level, several specific ministerial regulations act as guidelines to manage many
aspects of Lake Toba’s water. For example, on water usage, there are Ministry of Public Works
and Housing Regulation No. 9/2015 on water resources utilization and Ministry of Public Works
and Housing Regulation No. 37/2015 on the licensing of water use.
On wastewater, guidelines are provided in the Ministry of Environment and Forestry Regulation
No. 68/2016 on standards of wastewater management and in the Ministry of Public Works and
Housing Regulation No. 4/2017 on domestic wastewater management systems. For
implementation, the Regional Planning Agency and Ministry of Public Works and Housing
assembled working groups to prepare a Sanitation Strategy for Districts and Cities (or SSK).
The SSK prepared by working groups in the Lake Toba area so far only considers domestic
wastewater and does not consider waste from industry or aquaculture. On top of this, the
working groups have established sanitation roadmaps at province and district-level. One of the
requirements to submit a request for funding (sanitation budget proposal), is the establishment
of Local Community Support Groups (or KSM) to encourage local participation. Several of these
community groups already exist in the Lake Toba area. Other active groups at the community
level include Family Welfare Management Groups (or PKK).
The Presidential Regulation No. 49/2016 was issued to accelerate Lake Toba as a tourism
destination. In early 2016 President Joko (Jokowi) Widodo urged his Cabinet to accelerate the
development of the ten priority tourism destinations, including Lake Toba. The Regulation
instituted a new body, the Lake Toba Tourism Area Management Authority. The Coordinating
Ministry for Maritime Affairs is appointed as chair of the board. Presidential Regulation No.
49/2016 provides the Lake Toba Tourism Area Management Authority with (in article 2.2.2) the
authorization to develop a new tourism area of about 500-600 hectares and (in article 2.2.1)
the coordinating role for the area included in the Presidential Regulation 81/2014. This latter
area covers the whole of Lake Toba and its riparian land.
3.4.3 International setting
In 2014, Toba Caldera was designated by the President of Indonesia as a National Geopark of
the Republic of Indonesia with its distinct features as having a caldera of a super volcano and
uniqueness as the largest Quaternary Tectonic-Volcano in the world. The Toba Caldera was
targeted to be part of the Global Geopark Network (GGN) of UNESCO. The Lake Toba Tourism
Area Management Authority and the Executing Agency of Geopark Caldera Toba have
submitted their request for registration and are (as of February 2018) waiting for formal approval
by the GGN of UNESCO. If approved, the Government of Indonesia will be responsible to
maintain the ecological, archaeological, historical and cultural values with respect to local
economic development through conservation, education and tourism.
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3.4.4 Licensing and permits
Based on government regulation no. 69 (2014), any request for water usage of Toba should be
submitted to the Ministry of Public Works and Housing (PUPR). Such license proposals must
include a technical recommendation from the technical agencies at district or provincial level.
All recommendations must be approved by the water resources manager (BWS-S2). Applicants
can start the process by trying to get this recommendation first and then submit the complete
file to the Ministry. The technical recommendation includes technical concerns and considers
issues such as the type of water use, whether it is allowed at all; the location of the intended
water use; how the water will be taken and used; how, in the case of buildings or facilities, these
are designed; whether the intended water use will influence the water balance (neraca); and
what is the current condition of Lake Toba. Based on the technical recommendation, the
Ministry then makes one of three decisions: return the proposal and ask for more required
documents; issue the license (for a maximum of 10 years); or reject the proposal.
Typically, the licensing authority is located at the provincial and district levels. For international
investors, the central level plays a role, though this is a principle permit based on
recommendations from the province or district level. If permit requests are denied at the central
or provincial level, or if the process of technical recommendation takes too long, requesters
apply at the district level. There are no district-level services from the Ministry of Marine Affairs
and Fisheries in all districts, so at this level technical recommendations cannot always be
provided. As a result, despite the guiding rules that the process for issuing licenses should be
the same at all levels of government, permit granting at the district level tends to be more lenient
than at the provincial level.
3.4.4.1 Licensing for aquaculture
Local aquaculture started in Haranggaol Bay around 1996 with support from the local district of
Simalungun. The districts agreed with these new activities as they contributed to reducing the
high unemployment rates in the area. No formal licenses have been issued for the production
locations operated by local communities in Haranggaol Bay or elsewhere around Lake Toba.
However, the total local production potential, based on the number of cages, was estimated at
about 50,000 tons of fish annually in 2015.
Between May 2016 and June 2017, some of the district governments around the lake requested
the local communities to abandon aquaculture, because its foul odours hamper tourism and out
of concern for the water quality. Since then, many local fish cages have disappeared or are no
longer maintained. According to a fish farmers’ association, local aquaculture farmers in
Haranggaol have not received such a request from their local authorities, the Simalungun
district. Since the request of the local district governments, the estimated potential for small
scale production by communities has dropped to around 40,000 tons per year, most of it in
Haranggoal Bay.
Large and foreign commercial fish farms follow different procedures. For PT Aquafarm
Nusantara, being a foreign company, the license agreement was issued in 1998 through the
Investment Coordinating Board (BKPM) (personal communication with PT Aquafarm
Nusantara12). This license allows PT Aquafarm Nusantara to produce 36,000 tons of fish per
year. It is unknown when this license might expire. During the past few years PT Aquafarm
12 Letter from I Wayan Mudana, Director of PT Aquafarm Nusantara, to Deltares dated July 28th, 2017.
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Nusantara voluntarily reduced production to about 30,000 tons because of water quality
concerns based on their own monitoring program and external concerns.
For the domestic company, PT Suri Tani Pemuka, a subsidiary of PT Japfa Comfeed Indonesia,
the main production license is issued under the guidance of the Ministry of Marine Affairs and
Fisheries, but is managed at the provincial level. The license was issued for the period 2012 to
2016 and allowed PT Suri Tani Pemuka to produce 30,000 tons per year. As its licence expired
in February 2016, PT Suri Tani Pemuka is currently applying for a new license (from the Ministry
of Spatial Planning) to comply with the Toba Spatial plan. In 2016 PT Suri Tani Pemuka
produced around 4,000 tons per year but it intends to increase production and grow to the
maximum of 30,000 tons as soon as all licenses have been obtained13.
Both commercial companies, PT Aquafarm Nusantara and PT Suri Tani Pemuka have
requested technical recommendations from BWS Sumatera II to support their licence proposal.
Till now, the requests have been rejected, so from the point of view of BWS Sumatera II, both
companies are currently operating without a permit. Table 3.1 summarizes the available
information on licenses.
Table 3.1, Aquaculture licenses for Lake Toba (in tons of fish per year).
Producer License
period
2012-2016
Sources Licence in
November
2017
Sources
PT Aquafarm Nusantara 36,00012 Letter from
Mr. Mudana,
201712
unknown
PT Suri Tani Pemuka 30,000 Toba
Tilapia,
2016
0 BWS
Sumatera II
Haranggoal Bay 0 Stakeholder
meetings
0 Stakeholder
meetings Other smallholders 0 0
3.4.4.2 Other license requirements
The development of a (major) building, such as a hotel, requires the provision of wastewater
facilities as part of the building permit. Sanitary facilities of buildings are the responsibilitiy of
the district agencies, guided by the Directorate General for Human Settlements of the Ministry
of Public Works and Housing. Recommendations need to be issued by the relevant district level
agencies before the permit to develop the building is issued by the head of the district. The
District Licensing Agency and the District Environmental Agency currently do not systematically
monitor the discharge of wastewater.
The issuance of permits related to hydropower generation is handled by three different bodies.
The Ministry of Public Works and Housing (PP 69/2014, as described above) provides permits
for water usage. The Ministry of Energy and Mineral Resources provides permits related to the
generation of electricity. The Ministry of State Enterprises provides permits for businesses
(Permen PUPR 4/2014). The operation of the turbines for hydropower generation highly relates
to the water level of Lake Toba, so hydropower management would have to adhere to
13 This amount has been used in Scenario B.
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procedures from both the Ministry of Energy and Mineral Resources and the Ministry of Public
Works and Housing.
For any changes in land use, such as the implementation of wastewater infrastructure,
permission is not easily obtained. Much of the land surrounding Toba belongs to local clans or
communities (masyarakat adat) and has cultural significance. Any changes and regulations in
the land need confirmation and approval from all families involved.
3.5 Legislation vs implementation
After the Water Resources Law No.7 Year 2004 was revoked through the Constitutional Court
(Order No. 85/PU-XI/2013), the Lake Toba Ecosystem Management Plan was not
implemented. Currently, the general policy and strategic plans are made by the central level
government, while the implementation of most practical measures is carried out at the district
(or kabupaten) level. This includes the issuing of permits for, for instance, drinking water, waste
water, aquaculture, and land use change.
The cooperation and acceptance of the recommendations by the districts is required for
successful implementation of proposed programs. Since 1998, most of the proposed programs
and interventions lacked this support. The lack of official establishment of procedures and lack
of local linkages, as well as no “active” agreement on the National level with the Ministry of
Home Affairs are the main “dysfunctional features” or “bottlenecks” for the implementation of
different well-formulated and urgently-required programs to safeguard and improve the
environment and water quality of Lake Toba.
Implementation of legislation is also dependent on monitoring and enforcement efforts on the ground. For instance, there is no enforcement or penalty for hotels and buildings that do not have permits or wastewater facilities. Licenses are issued by the District Licensing Agencies with recommendations by the relevant district line agencies. However, because of the lengthy process of the technical recommendations, absence of relevant district agencys and lack of coordination, many hotels and other investors abandon the process. Many hotels surrounding the lake do not apply for permits at all.
The planning and execution of erosion control and reforestation is the domain of the national
and sub-national government agencies of the Ministry of Forestry, implemented through a top-
down approach. Local communities, non-governmental organizations, and members of the
private sector have been involved in restoration and reforestation efforts, although their
work has been limited in terms of scale, funding, and geographic scope relative to the
government’s efforts. Unfortunately, from the government’s side, there are regulations and
actions that could undermine the erosion control and reforestation efforts. For example,
Presidential Regulation No. 49/2016, which was issued to accelerate Lake Toba as a tourism
destination, contains a section about re-zoning. This means that some areas surrounding the
lake, currently classified as “protected forest”, could be converted and used for other purposes
such as tourism in a fast-tracked process. Other threats to the forests near Lake Toba include
legal and illegal logging, as well as uncontrolled burning (see e.g. Hadinaryanto et al., 2014;
Gunawan, 2016; Sitanggang, 2017). If unchecked, illegal logging could greatly undermine the
efforts to restore forests in the Toba landscape.
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4 Stakeholders and Governance
4.1 Approach
The stakeholder mapping and assessment uses the stakeholder roles as recognized by the
Indonesian water laws (Annex H.1.1) and reflects the social network analysis conducted in
2017 (Annex H.1.2). It identifies for each actor involved in monitoring and managing the Lake
Toba Asahan catchment, his or her specific roles, interests and responsibilities. Based on the
result of the stakeholder mapping, different groups of stakeholders were categorised as “co-
knowers”, “co-thinkers”, or “co-operators”.
The stakeholder assessment and mapping was based on the (2013-2015) Basin Water
Resources Management Council (Tim Koordinasi Pengelolaan Sumber Daya Air, TKPSDA)
process, in combination with recent (and on-going) processes. Stakeholders have been
identified in the Germadan Toba (Lake rescue initiative) process of the Ministry of Environment
and Forestry (Kementerian Lingkungan Hidup dan Kehutanan, KLHK), by the Environmental
Sustainability Authority for Lake Toba (Badan Koordinasi Pelestarian Ekosistem Danau Toba,
BKPEDT), by the Provincial Environment Agency (Dinas Lingkungan Hidup, DLH), and as part
of the Urban Sanitation Development Program (USDP). This assessment also builds on the
stakeholder mapping and assessment for the Basin Water Resources Management Plan
(2001-2004, Perencanaan Pengelolaan Sumber Daya Air Wilayah Sungai, BWRMP), which
was verified and updated. Insights from these earlier assessments were used to identify
stakeholders and structure the meetings.
Semi-structured interviews, meetings with the Reference Group, and the wider stakeholder
consultations as part of the WQ Roadmap assignment provided further insights into the views
of key stakeholders (Annex A). Social network analysis was performed as part of these
meetings, resulting in new NetMaps. The NetMap exercises and resulting maps (Figure 4.1
and Figure 4.2) helped identify additional stakeholders and showed which stakeholders play a
key role in water quality monitoring and management at Lake Toba.
4.2 Stakeholder mapping
4.2.1 Mapping
Two meetings were organised to map the stakeholders involved in water quality at Lake Toba
through NetMap analysis (Annex H.2.1): the first in Jakarta, and the second in Laguboti
(Sumatra), with a larger group. The involvement of the reference group in both meetings provided
an opportunity for reflecting on elements of the management of Toba Lake water quality, and
in understanding the dynamics in the management of water quality in Lake Toba without
conducting elaborate questionnaires. The discussion focussed on the key question: “Who
Influences the water quality management of Lake Toba?”
The meetings started with the identification of stakeholders (actors and actor groups), without
referring to ealier mapping processes. This allowed for a strong focus on water quality.
Subsequently, two important flow types between them were defined in relation to Lake Toba
water quality: authority and information (or coordination). In Figure 4.1 and Figure 4.2 these are
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represented in blue arrows for authority and in yellow arrows for information or coordination.
Solid lines represent formal flows and dotted lines point at informal flows. The size of the circle
for each actor illustrates relative influence: the larger the size of the circle, the higher the
influence of this stakeholder on the management of water quality.
Figure 4.1, Social Network Map from the first NetMap exercise on the influence on water quality management in
Lake Toba, as produced with the reference group on May 17, 2017.
The first meeting, held in Jakarta with 27 participants, produced a social network map (Figure
4.1) with a total of 248 connections. Assuming that coordination is a two-way relationship and
authority is a one-way interaction, the total number of linkages would be 496 (the “arrow heads”
in the figure). The map indicates the presence of several hubs that are highly connected and
have significant influence over the network. These hubs include the Basin Management Center
Sumatra II (or BWS Sumatera II), the Coordinating Ministry of Maritime Affairs (or Kemenko
Maritim), the Governor of North Sumatra (or Gubernur SU), the Ministry of Public Works and
Housing – Directorate General Water Resources (PUPR SDA), and the Ministry of Environment
and Forestry (KLHK). These key stakeholders are described in the next section 4.2.2.
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Figure 4.2, Social Network Map from the second NetMap exercise, building on the first NetMap exercise,
produced with more participants at the local level on June 14, 2017.
The 55 participants at the second meeting, held in Laguboti (Sumatra), identified more
local actors, for example traditional leaders. These additional stakeholders and
connections enriched the discussion on the management of Lake Toba. Hence the second
network map (Figure 4.2) shows more stakeholders in the map, with more connections,
especially at the sub-national level. At the second meeting, 389 connections have been
identified. With that coordination displayed as a two-way relationship and authority as a
one-way interaction, the total number of linkages would be 778. Interestingly, the hubs
stayed relatively unchanged even after more stakeholders were added to the map. With
more sub-national actors added to the map, a few new linkages were identified between
the sub-national actors. For example, Bappeda Kabupaten (District Planning Agency)
emerged as a hub for the district agencies. Annex H.3 includes some of the rich
discussions around the maps. Main findings are included in sections 4.2.2 and 4.3, while
the overall analysis of stakeholders and institutions is the scope of section 4.4.
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The NetMap process shows how the various government agencies are not as connected
with other actors (private sector, academia, and local communities), as it should be for
good communication and coordination.
The network map process helped prioritize actions by identifying the actors with the
perceived highest negative influences to the Lake (highest polluters). State actors are not
the only actors actively involved as for instance civil society organizations (CSOs) play a
significant role in shaping the water quality agenda. The net map shows that CSOs are
highly connected with each other and with other types of actors at different levels (national
and subnational). The local CSOs have attempted to influence water quality management
through a range of activities from public education, advocacy, environmental protection
and conservation, to information exchange. Many of the CSOs, such as Yayasan Pencinta
Danau Toba (YPDT), WALHI, Alusi Tao Toba, KSPPM, and local communities,
represented through DAERMA (Local Fishermen’s Association), expressed that often
when their aspirations are not well-received by the district services, they would go directly
to the relevant ministries at the national level.
Targeting actors with the highest negative influence could support lake management
intervention and enhance potential impact.
4.2.2 Key stakeholders
A total of 91 stakeholders were identified during the NetMap exercises. This number is an
under-representation of the actual number of stakeholders involved. For instance, certain
district level agencies were listed only once to represent all eight districts surrounding Lake
Toba. If all district level agencies were to be included, the number of actors would be 170.
An overview has been made of all stakeholders at Lake Toba with their key role as
regulator, coordinator, operator, developer or user (see Annex H.1.1 for an explanation of
these roles), the level at which they operate, type of organization and the sector. The full
list of stakeholders is presented in Annex I. Below the most important stakeholders are
briefly introduced with their mandate and main activities.
Table 4.1, Main stakeholders at the central government level with their mandate and activities in relation to
water quality of Lake Toba.
Institution Activities Involvement
Coordinating
Ministry of Maritime
Affairs
Coordinates Ministries of:
Transportation; Marine and Fisheries; Tourism;
and Energy and Mineral Resources
The Board chair of
BOPDT is from this
ministry; the head of
implementation is from
the Ministry of Tourism
(perspires 49/2016,
clause 5)
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Institution Activities Involvement
Coordinating
Ministry of
Economic Affairs
Coordinates Ministries of:
Public Works and Housing; Forestry and
Environment; Finance; Industry; Trading;
Labour; Agriculture; Agraria and Spatial
Planning; State Owned Companies;
Cooperative and small enterprise.
Through several of the
ministries it coordinates.
Ministry of
PPN/National
Planning
Agency/Bappenas
(Sub Directorate
General of River,
Coastal, Reservoir,
Lake)
Coordination and policy formulation on
development planning, national development
strategy, sectoral, cross-sectoral, and trans-
regional policy directions, national and regional
macroeconomic frameworks, infrastructure and
infrastructure design, regulatory, institutional
and funding frameworks, and monitoring,
evaluation and control of the implementation of
national development.
National planning
agency, especially for
national priority
programs (e.g. tourism);
Planning of rivers,
reservoirs and lakes
influences Lake Toba.
Ministry of Tourism
Formulation and determination of policy on
tourism destination and tourism development,
development of foreign tourism marketing,
development of tourism marketing of
archipelago, and development of tourism
institute.
Tourism industry is a
polluter (via solid waste
and wastewater) and an
employer and potential
ally for improved water
quality; Lake Toba is a
priority tourism
destination.
Ministry of
Environment and
Forestry
Formulation and policy making on sustainable
forest and environment conservation,
conservation of natural resources and their
ecosystems, improvement of watershed
support capacity and forest protection,
sustainable forest management, enhancement
of forest industry competitiveness, quality of
environmental functions, control of pollution &
environmental degradation, climate change
adaptation and control of negative impacts,
forest & land fire control, social forestry and
environmental partnerships.
A substantial area
around Lake Toba is
classified as forest
estate, which is under
the purview of this
Ministry. Environmental
issues touch upon many
other sectors, hence the
broad involvement of this
Ministry.
Ministry of Agraria
and Spatial Planning
Formulation, determination, and
implementation of policy in spatial planning,
infrastructure of agriculture, land affairs, land
use, and soil.
Pres. Reg. 81/2014
(spatial plan of lake
Toba/NSR) has to be
monitored by this
Ministry
Ministry of Public
Works and Housing
(MPWH)
Formulation of water resources under DGWR,
wastewater management, sanitation, and
waste management under DG Human
Settlements, and management of lakes in the
Center of Lakes and Reservoirs, roads under
DG Bina Marga (PIPR)..
Management of water
resources, wastewater,
and sanitation; integrated
tourism master plans.
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Institution Activities Involvement
Regional
Infrastrucutre
Development
Agency (RIDA),
MPWH
Preparation of technical policy and integrated
strategy of regional development (under
Ministry of Public Works and Housing).
Preparation of integrated
tourism master plan for
several tourism
destinations (including
Lake Toba)
BWS Sumatera II
Water resources planning and management of
upstream conservation, water quality, water
utilization, control of destructive water,
operation and maintenance, rehabilitation,
construction/development.
Water quality monitoring
Center Research of
Water Resources Research
Water quantity and
quality
Ministry of Marine
Affairs and Fisheries
Formulation, determination, and
implementation of policies on marine, and
freshwater fisheries and aquaculture
Aquaculture is a polluter
and employer.
Ministry of
Agriculture
Formulation and issuance of policies on
provision of agricultural infrastructure and
facilities, increasing production of meat, rice,
corn, soybeans, sugarcane, and other crops,
as well as enhancement of added value,
competitiveness, quality, and marketing.
Agriculture is an
employer and a polluter
(especially livestock)
Ministry of Industry
Formulation, determination, and
implementation of policies for industry;
technical guidance and supervision over
implementation of policies for industry.
Local industries (e.g.
TPL) are polluters and
employers.
Ministry of State
Owned Companies
Implement water resource commercialization,
Water resource services in water resource
utilization by users; provision of guarantee for
water resource services to users through
operation, maintenance and development of
water resource infrastructure; provision of
technical advice to water resource managers
authorized to prepare technical
recommendations for water resource
commercialization; implementation of operation
and maintenance of water resource
infrastructure, for which operation is handed
over to the company.
State-owned companies
around Lake Toba, such
as PJT1. The Ministry
can collect fees from
water users.
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Institution Activities Involvement
Badan Otorita
Pariwisata Danau
Toba (Lake Toba
Tourism Area
Management
Authority; 2016 -
2041)
Preparation of Master Plan and Detailed Plan
of Development of Tourism Area of Lake Toba;
implementation of coordination and policy
strengthening of planning, development,
management, and control of Lake Toba
tourism area; formulation of operational
strategy of tourism development of Lake Toba
area; assistance to development of tourism in
the area around Lake Toba, facilitation and
stimulation of tourism growth in the Lake Toba
area; implementation of licensing and non-
licensing business centers and areas in the
region of approximately 500 ha in the Tourism
Area of Lake Toba; determination of strategic
steps to solve problems in planning,
development, management, and control of
Lake Toba tourism area.
Preparation of detailed
plan,14 coordinating
implementation of master
plan, management of
500 ha tourism area
Supports momentum for
water quality
improvement
Investment
Coordinating Board
/BKPM
Coordination in national level for
investment/investor; national one-stop-shop for
investment (for large domestic investors or
foreign investors)
Licensing for investors
(e.g. in aquaculture),
including foreign
investors
Table 4.2, Main stakeholder at the provincial level with their activities in relation to water quality of Lake Toba.
Institution Activities
Provincial Environment
Department North
Sumatra (DLH-SU)15
Determination of carrying capacity and environmental capacity; Determination of environmental quality standards; Determination of the pollution quality standard for the main sources; monitoring and conservation of biodiversity; development and empowerment of communities in waste management; facilities and infrastructure for sewage treatment; water quality monitoring; monitoring of pollutant sources; pollution prevention (provision of information, isolation and termination) of pollutant sources; recovery of pollution (cleaning, remediation, rehabilitation and restoration) of pollutant sources; regulation of pollutant sources
Badan Pengelola
Geopark Kaldera Danau
Toba
Special body (initial) for Lake Toba Geopark, as required by UNESCO
BKPEDT Coordination for ecosystem, including water quality
Forum DAS (Daerah
Aliran Sungai) Coordination forum for upstream catchment
PU province Takes care of river basins that belong to the province (Permen PUPR
4/2015)
14 It has been agreed between government agencies/ministries that RIDA of MPWH will prepare the Integrated
Tourism Master Plans. 15 Before January 2017, DLH-SU was named BLH-SU, Badan Lingkungan Hidup - Sumatra Utara: the Provincial
Environment Agency - North Sumatra.
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Table 4.3, Main stakeholders at district level with their activities in relation to water quality of Lake Toba16.
Institution Activities
Head of District
Licensing authority for fish cages and hotels, based on
technical recommendation from related agencies
Regional Planning Agency/
Bappeda Kab.
Coordinates planning from all sectors at district level
District PU Takes care of river basins that belong to the district
Table 4.4, Other major stakeholders with their activities in relation to water quality of Lake Toba.
Institution Activities Involvement
Various NGOs Depending on their interest Some do monitoring
PDAM Tirtanadi Drinking water and wastewater
company
Manages wastewater
treatment plant (IPAL) Parapat
Electricity companies
(e.g. BDSN, INALUM,
PLN)
Hydropower Water user
TPL (Toba Pulp
Lestari) Pulp company Polluter and employer
PT Aquafarm
Nusantara Aquaculture Polluter and employer
PT Suri Tani Pemuka Aquaculture Polluter and employer
National Water
Resources Council/
Dewan Sumber Daya
Air Nasional
Preparation of national water resources
policy
Water quality is one aspect in
policies
Basin Council/
Tim Koordinasi
Pengelolaan Sumber
Daya Air Wilayah
Sungai
Coordinates water resources
management at basin level; endorse
strategic and master planning, global
and yearly water allocation,
implementation matrix on hydrology,
hydrogeology and hydro-climatology,
monitoring program and activities
Water quality is one aspect of
water resources conservation
4.3 Stakeholder assessment
The discussion and resulting NetMaps illustrate that management of water quality in Lake
Toba is complex and dynamic. The actors with many hubs (highly connected network) are
mostly at the central level. The second map (Figure 4.2) shows that there are few
connections at the sub-national levels (both at provincial and district levels, but especially
at the district level), to the rest of the actors on the map. These few connections are mainly
limited to other governmental entities, and rarely with the private sector, academia, or
16 In 2016 there were no agencies at district level for forestry, environment and aquaculture.
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others. There seems to be little collaboration between government agencies in different
sectors, nor between various levels. This confirms perceptions reflected in the first NetMap
(Figure 4.1), suggesting that the central level actors are more vocal and more involved in
the management of Lake Toba.
The NetMap itself did not capture actors that may influence water quality in Lake Toba but
have very limited interest in improving lake water quality or reducing pollution. The
discussion helped to identify them (for instance in aquaculture, livestock, tourism, mining).
There are several coordinating bodies (e.g. Forum DAS, TKPSDA, and BKEPDT) to
manage the water quality of Lake Toba but the NetMaps do not show a clear leader or
champion. This may be because these organizations have been initiated at national or
provincial level, with little focus on the district level. The hubs with intensive interaction
indicate the potential of some stakeholders to become champions or change agents
toward the better management of Lake Toba water quality.
It might be worth exploring the CSOs’ potential to guard the management process of Lake
Toba, considering their active participation and monitoring on the issue, and their close
relationships (formal and informal) with different kinds of stakeholders. From the
discussion at the second workshop, the CSOs emerged as having been engaged with
each other as well as with the local communities. They have been pressuring many
changes in the government and private sector as well.
4.4 Governance for monitoring and management of Lake Toba
4.4.1 Approach
The NetMaps (section 4.2.1) show relationships between actors. However, the strengths
and gaps in their governance are not apparent on the map, especially regarding the
capacity to monitor the implementation of programs, including the issuance of permits and
law enforcement. Thus, a separate analysis identifying strengths, weaknesses,
opportunities and threats (SWOT) has been conducted at the meetings for various sectors.
SWOT analyses help to identify internal strengths and weaknesses, as well as its external
opportunities and threats of an organization, initiative or sector. In this case, benefitting
from the expertise of the Reference Group present at the meetings, the analysis focused
on aspects that have an impact on the water quality of Lake Toba.
After separate SWOT analyses had been done for different stakeholders and processes
associated with water quality monitoring and management at Lake Toba, an overall
analysis could be made.
4.4.2 Overall SWOT
The following areas have been considered in identifying strengths, weaknesses,
opportunities and threats for the WQ Roadmap (Figure 4.3):
• Resources available: Labour, capital, management skills, technology, funds
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• Physical environment: Climate, severe weather events, volcano eruption, pests and
diseases
• Infrastructure factors: Roads, transport, Integrated Water Resources Management
(IWRM) infrastructure
• Economic factors: Livelihood issues, markets, tourism
• Social factors: Residents attitudes towards use of the lake, sanitation and waste
management, legal and institutional aspects, and key stakeholders.
Figure 4.3, SWOT framework for Lake Toba water quality monitoring and management.
Main strengths are defined as current positive circumstances that support the monitoring
and management of water quality. The main weakness would then consist of the opposite,
a negative or unfavourable condition that hampers the success of monitoring and
management of Lake Toba. Opportunities consist of innovative ways to make the
monitoring and management more successful, to create an environment that is more
favourable. Finally, threats are defined here as events or conditions that, if these would
happen, will harm the monitoring and management of Lake Toba. The factors shown in
Figure 4.4 have been identified as crucial strengths, weaknesses, opportunities and
threats to the implementation of a water quality roadmap for Lake Toba.
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Figure 4.4, Overall strength, weakness, opportunity and threat (SWOT) analysis of water quality monitoring and management of Lake Toba and its catchment area.
Strength
• The heightened momentum due to President Jokowi’s designation of Toba as one of the priority areas for tourism development.
• Wastewater treatment facilities and regulations were set up due to expected tourism activities (under decentralization law UU 23/2014, sanitation is a priority, triggered by the NSR).
• Strong demand and pressure for clean water in and around Toba, as reflected in infrastructure, initiatives, programs.
• Decentralization; provinces have more capacity and resources for operations and implementations.
• Provincial agency now handles management of solid waste.
• Reference and guidance for Lake Toba management is available from Lake Rescue Initiative and other studies. The letter from the Minister of Environment and Forestry (MENLHK/PPKL/PKL.2/4/2017) provides direction.
• Increasing public participation, with communities interested to comply and NGOs actively participating and involved in monitoring.
Weakness
• Not all eight districts have formally committed.
• Gaps between initiatives at the central level and implementing bodies at the district level.
• Limited monitoring and enforcement capacity in law compliance.
• Poor state of existing wastewater treatment plants.
• Low coordination between the license issuing agencies and the relevant technical services at the district level.
• Lack of legally binding regulations for the Lake Rescue Initiative to implement a management program.
• Diffuse responsibilities because of overlapping mandates between institutions.
Opportunity
• National programs as incentives for better management: Adipura, Social Forestry Program.
• High interest from the President to preserve Lake Toba, could be used to get other government bodies actively involved.
• Lake Toba as a priority National Strategic Region receives a lot of attention.
• Interest from the Coordinating Minister of Maritime Affairs could further push development of infrastructure around Lake Toba.
• Lake Toba Tourism Area Management Authority Board has a specific mandate
• The Government is in the middle of preparing an integrated tourism master plan.
• The presence of local community support groups (KSMs) could be used for information sharing, to advocate better management and to promote new intervention programs.
• Willingness of community members to change jobs, especially to tourism.
Threat
• Much of the land surrounding Lake Toba has cultural significance. Any changes in land use need customary approval from all families and clans. This long process could hamper the timely implementation of basic infrastructure.
• Lake Toba Tourism Area Management Authority Board is allowed conversion of areas around the lake, including those currently classified as “protected forest”, into other uses in a fast-tracked process.
• If fish production would be limited, jobs could be lost, possibly without alternative livelihoods, potentially leading to social conflicts or legal disputes.
• Political changes at national and provincial level could affect the strong commitment to restore the lake.
• Potential conflict of interests when government officials are involved in industry, such as fishing industry, or paper mills.
Monitoring and Management of
Lake Toba
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4.4.3 Synthesis
Overall, the heightened momentum to make Lake Toba a tourism destination has provided a
strong push for new initiatives and program to revive Lake Toba. The agenda for management
of Lake Toba is pushed at the national level, through the President, the Coordinating Ministry
of Maritime Affairs, the Lake Toba Tourism Area Management Authority, and the Ministry of
Environment and Forestry through the Lake Rescue Initiative. This agenda provides a window
of opportunity to accelerate the improvement of Lake Toba’s water quality. The heightened
interest allows more resources, be it human resources or financial resources, allocated to
support pollutant intervention in Lake Toba.
Regardless of this strong push, the bottleneck in the management has been at the district level,
where monitoring and law enforcement efforts happen. Currently, the district heads have not
shown strong commitment to manage the lake or may lack the capacity (where no fishery
agencies are present at district level, technical recommendations for licenses cannot be given).
As observed on the ground, there is weak maintenance of existing facilities, such as the waste
disposal sites or wastewater treatment plants. There is a lack of coordination between the
district that issues licenses and relevant district services. This is a major unfavourable condition
that will hamper the management efforts of the Lake Toba area.
To respond to this drawback, hence, a legal regulation to bind commitments on the district level
is urgently needed. The Governor could use his legal intervention power to instruct and guide
the Districts. In the past, the Ministry of Home Affairs has proven itself to be an effective body
to instruct district heads to build sanitation facilities. Direct implementation by provincial
agencies to take over management role is seen as positive, since provinces have more capacity
and resources (human resources and budget) for operations and implementations than the
districts. It is crucial for the provinces to do monitoring efforts and enforce the already existing
laws to ensure that all stakeholders abide by the regulations. It is also important for the governor
to actively voice a strong commitment to Lake Toba area management.
Local residents, including civil society groups (CSOs), have expressed support and are eager
to follow management programs and obey the laws. This includes farmers who have shifted
from horticulture to aquaculture. Though they are operating without a license, they have
expressed a keen interest in alternative livelihood options. There are active CSOs engaging
with residents and voicing concerns on the resident’s livelihoods. Residents have a strong
attachment to Lake Toba for its cultural value.
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5 Drivers and Pressures: nutrient inputs
5.1 Approach: the Sumatra Spatial Model
The Lake Toba catchment area was analysed with an adapted version of the Sumatra Spatial
Model (Annex J). The same spatial model has been applied in Indonesia to predict impacts on
water resources systems in earlier studies, such as the Java Spatial Model developed for the
ADB study for the 6 rivers around Jakarta (6Ci study); the World Bank-financed Java Strategic
Water Resources Study (JWRSS); and the Korean study for Strategic Water Resources of
Sulawesi.
5.1.1 Calibration of population growth
For the year 2015 a comparison was made of the population data according to the Dalam
Angka statistics by district found in the Lake Toba catchment area (Table 5.1). It is found that
the population growth 2010-2015 in this period is over-estimated by the Sumatra Spatial Model
as growth for Sumatra as a whole is set at about 3% annually. However, average growth for
the Lake Toba districts (Figure 7.1) is only about 1% annually according to the Dalam Angka
and about 2% in the Sumatra Spatial Model. In the drivers of SSM the growth reduces rapidly
after 2015. Therefore, it is expected that this difference in growth is only in the beginning of the
projection period.
Table 5.1, Comparison of 2015 Dalam Angka population with results from the Sumatra Spatial Model (SSM).
2015 population SSM/Dalam
Angka District Dalam Angka SSM
Tapanuli Utara 293,399 301,609 102.8%
Toba Samosir 179,704 189,917 105.7%
Asahan 706,283 739,829 104.7%
Sima Lungun 849,405 899,582 105.9%
Dairi 279,090 296,631 106.3%
Karo 389,591 391,915 100.6%
Humbang Hasundutan 182,991 185,717 101.5%
Samosir 123,789 132,155 106.8%
A proper comparison can only be made in the next population census. As the model
overestimates the waste load calculated by SSM, it is on the safe side for the water quality
analysis. Therefore, at this stage no further attempt to calibrate the spatial model for the Lake
Toba region was made. This can be considered at a later stage when making a more detailed
study of the Lake Toba water quality at present and in the future.
5.1.2 Load calculations
To quantify the importance of the current sources of nitrogen and phsphorous, load calculations
were performed on the basis of this model. These calculations and the SSM model also project
socio-economic developments, future land use and the corresponding nutrient and waste loads.
The assessment of key drivers is based on emission estimations for point and non-point
sources in the year 2015, across the selected zonation option to divide the lake into four
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compartments. After the loads have been calculated, total nitrogen (TN) and total phosphorous
(TP) concentrations are calculated for each of the compartments witha simple budget model
approach (Annex J). Below the model settings and assumptions are provided with respect to
emission and run-off factors per source.
Aquaculture
Emissions for the whole lake are calculated as the product of annual fish production (tons of
fish/year) and the nitrogen or phosphorous loss to the environment per ton of fish production.
The phosphorous loss is estimated as 15.98 kg per ton of fish, by applying a food conversion
ratio of 1.9 to the values estimated by Oakley (2015, Table 1). The nitrogen loss is taken as 6
times the phosphorous loss (based on Table 4 in Gyllenhammar and Hakanson, 200): 74.78
kg/ton fish. The total load is distributed over the various lake model compartments based on
the ratio of their surface.
For 2015 the total production based on DLH-SU 2017 was taken: 84,800 tons. However, the
distribution over the various producers, as suggested by DLH-SU in Table 2.3), could not be
justified based on observation. A GIS analysis (the data behind Figure 5.1) determined the
number of fish cages across Lake Toba. As the fish cages of smallholders outside Haranggoal
Bay varied over time (section 2.1.4), a weighing factor of 0.5 has been applied to estimate the
number of cages in 2015. Subsequently, the total production of 84,800 tons has been
proportionally distributed over the fish cages, assuming that commercial fish cages produce
twice the amount of smallholder cages. Emissions however, are set at the same value for
commercial and smallholder fish cages as commercial aquaculture operate more efficiently
(Table 5.2).
Table 5.2, Estimated fish production in aquaculture at Lake Toba in 2015 across the compartments per group of
producers (in tons of fish per year, with total production estimates by DLH-SU and geographical distribution
according to Figure 5.1).
Producers Estimated production 2015
N South S1 S2 S3 Total
PT Aquafarm
Nusantara
14,000 22,000 22,000 36,000
PT Suri Tani
Pemuka
9,700 0 9,700
Haranggoal Bay 22,700 0 22,700
Other smallholders 6,500 9,900 3,300 4,900 1,700 16,400
Total 52,900 31,900 3,300 26,900 1,700 84,800
Percentage
production
62% 38% 4% 32% 2%
Percentage
emission
60% 40% 8% 28% 4%
Livestock
Livestock counts are related to population numbers. The population forecasts per sub-
catchment provide growth factors to estimate the future load from livestock. The emission factor
for phosphorous is 384 ton P/year, based on DLH-SU (2017). The nitrogen load is taken as
three times the phosphorous load (i.e. 1,152 ton N/year) based on Buckley and Makortoff
(2004).
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Agriculture
Emissions are calculated as the product of cultivated areas, emission factors per crop or culture
type (g/ha/season) and the number of growing seasons per year (Table 5.3). The emission
factor for P was based on Iskandar (2013).
Table 5.3, Model settings for agriculture.
Emissions (g/ha/season) Number of
seasons
Runoff
factor N P
Total paddy area (ha) 20 10 3 1
Other agriculture (ha) 10 5 1 1
Plantation (ha) 3 1,5 1 1
Wastewater
Emissions are calculated as the product of population, emission factors per inhabitant
(g/person/day) and the runoff factor (Table 5.4). Emission factors were taken from DLH-SU
(2017) and Deltares & TNO (2016). The population numbers are based on national censuses
and the Sumatra Spatial Model and thus comprise only inhabitants of Lake Toba’s catchment
area (see Annex J).
Table 5.4, Model settings for domestic wastewater.
Emissions (g/person/day) Number of days
per year
Runoff
factor N P
Urban population 15 2,55 365 0,5
Rural population 15 2,55 365 0,5
The tourism load is estimated from a total of 5 million tourist night per year based on the Tourist
Demand study (Table 7.1). The resulting load is computed in a similar way as the domestic
loads (Table 5.4). The total tourist night are spread between the model compartments based
on the Tourist Demand Assessment (Nontji, 2016). Other land Use
For other land use, emissions are calculated as the product of land use areas and emissions
factors per land use class (Table 5.5). Phosphorous and nitrogen emission factors were based
on Iskandar (2013).
Table 5.5, Model settings for other land use.
Emissions (g/ha/year)
N P
Grass/Other (ha) 2,46 0,246
Shrub (ha) 2,46 0,246
Forest (ha) 1,94 0,194
5.2 Assessment of point and non-point sources
It is important to distinguish the potential sources to identify appropriate mitigation measures to reduce pollution loadings into the lake. From this perspective sources can be classified as point and non-point sources to guide infrastructure and other investments for potential mitigating measures. A classification for the most important drivers of pollution; aquaculture, livestock and domestic wastewater, is provided below with illustrative maps. However, for the water quality
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model a distinction between point and non-point sources is less important as it is assumed that each nutrient loading is immediately dispersed in a compartment up to the thermocline layer. Aquaculture
Theoretically, each fish cage could be considered as a separate point source. Mitigating
measures can be taken at farm level and from there at each individual cage.
Figure 5.1Figure 2.1 can serve as guidance to support targeted mitigating measures. In Figure 5.1 the dots represent clusters of individual fish cages as mapped from Google Earth images.
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Figure 5.1, Location of three types of aquaculture on Lake Toba, based on observations in Google Earth in the
period 2008-2015. Blue: clusters of long fish cages, as mainly found in Harangoal Bay; Green: clusters of
commercial fish cages; and Yellow: clusters and individual fish cages.
Livestock Numbers of farming animals in the models have been estimated from population growth in the Sumatra Spatial Model. Figure 5.2 shows livestock densities around Lake Toba, based on data from DLH-SU. Nutrient loads from manure mainly enter the lake via surface runoff and groundwater. Livestock can be classified as non-point source of pollution that roughly follow population densities. The same holds true for agriculture and other land use (minor contributions to nutrient loads only). The division into compartments extends to the catchment areas.
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Figure 5.2, Livestock densities around Lake Toba. Note that some data were available at desa level, some at district
level, and for other areas no data were available at all.
Wastewater
Most of the current sanitation facilities around Lake Toba are on-site facilities at household or
community level. Both in rural and urban areas most of the on-site systems do not comply with
the definition of a septic tank and are more like pit latrines. The one wastewater treatment plant
in the area is operating at only 10% of its capacity (section 8.4.2.1). As a result, a lot of polluted
water leaks to the groundwater. At times of high precipitation this is complemented by surface
runoff. Hence domestic wastewater can be classified as a non-point source ofpollution in the
catchment area, with concentrations following population density (Figure 5.3).
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Figure 5.3, Lake Toba catchment population density by desa in 2015.
Tourism numbers do not substantially increase the nutrient load from domestic wastewater, as
the numbers of visitors are low in comparison to the population density, though they are
concentrated in a limited number of desas (Figure 5.4). Hotels are generally small and even
without adequate sanitation facilities, the contribution of individual hotels can be compared with
a cluster of houses. Therefore, tourism can be classified as a non-point source.
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Figure 5.4, Main tourism areas around Lake Toba (based on Tourism Demand Assessment).
5.3 Total and relative nutrient loads
The modelled nitrogen (N) and phosphorous (P) loads for the year 2015 are shown in Figure
5.5, Figure 5.6 and Figure 5.7, with indications of the relative contributions of various sources
across the compartments. These figures clearly show that aquaculture is the main source of
nutrient loading, constituting 76% of the total N loads and 68% of the total P loads into the
whole lake. This is followed by domestic wastewater (sewage), responsible for 15% of the
nitrogen loads, and 11% of the phosphorous loads. The third main source is livestock, which
contributes 5% to the nitrogen loads and 19% to the phosphorous loads. Other sources of
nutrients include forests, meadows, tourism, sawahs and other agriculture, together
responsible for 4% of the nitrogen loads and 2% of the phosphorous loads (Figure 5.8).
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Nitrogen (N) loads in one compartment
Nitrogen (N) loads in two compartments
Nitrogen (N) loads in four compartments: N = north; S1, S2 and S3 are southern compartments
Figure 5.5, Relative contributions of various drivers to the total nitrogen (TN) load in various lake compartments in
2015, according to the load calculations based on land use and underlying SSM model.
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Phosphorous (P)
loads in one
compartment
Phosphorous (P)
loads in two
compartments
(N = north)
Figure 5.6, Relative contributions of various drivers to the total phosphorous (TP) load in one and two lake
compartments in 2015.
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Figure 5.7, Relative contributions of various drivers to the total phosphorous (TP) load in 2015, in four lake
compartments: N = north; S1, S2 and S3 are southern compartments.
Figure 5.8, Relative contributions of various sources to the total phosphorous load in Lake Toba as a whole in 2015.
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Tourism thus has relatively limited, if any, impact on nutrient loading – as evidenced from Figure
5.9.
Figure 5.9, Relative contributions of wastewater from residents (domestic loads) and tourists (tourist loads) for
nitrogen (top graph) and phosphorous (bottom graph) in four compartments of Lake Toba: N = north; S1, S2
and S3 are southern compartments.
The nutrient loads presented above are based on mixing in the lake compartments. In reality
there may be significant local effects that are not captured in the approach applied here. Hence
even in cases where the long term, far-field effects that are shown in this chapter are not very
large, the short term and local (near-field) effects may still be significant. LIPI calculated the
near field effects and these show that with increasing densities of fish cages, the water quality
may locally deteriorate to eutrophic and even hyper-eutrophic state, for instance along the
north-eastern coast (Table 5.6). This demonstrates that the findings in this report, showing
average values for entire compartments, could represent an under-estimation of the true local
pollution loads. On the other hand, local effects could also be very temporary, as influenced by
changes in local loads, winds and other factors.
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Table 5.6, 3D model results on the short term & near-field effects of nutrient loads resulting from aquaculture at various depths in Lake Toba (Figure provided as is by LIPI).
Density of
fish cages
Depth
1m 2m 10-15m 40-50m
0 cages/
segment
20 cages/
segment
100
cages/
segment
Each segment (pixel) is 250 x 250m
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5.4 Nutrient inputs
As part of the decision on the carrying capacity of Lake Toba, several key institutes and
universities have carried out a “pollutant source analysis” to understand the pollutant load
pathways in Lake Toba. Although the analyses differ somewhat, they all show the same picture,
which has been summarized by DLH-SU in their carrying capacity as proposed to the Minister
(DLH-SU, 2017; Figure 5.10): Phosphorus is identified as the most critical factor for water
quality. Other parameters are important as well, but for this Water Quality Roadmap the focus
is on the process of eutrophication with phosphorous as the main determinant. Findings on
nitrogen have been added to most sections as well.
Figure 5.10, Phosphorous loads to Lake Toba as reported by DLH-SU in ton/year (source: DLH-SU, 2017)
By far the largest nutrient loads originate from aquaculture, followed by animal husbandry and
domestic sewage (including tourism), agriculture and some very small other sources of
pollution. This is in agreement with the loadings calculated on the basis of the SSM model
reported in the previous section. Figure 5.10 also shows that the rate of daily phosphorous
contribution from aquaculture has doubled over the past four years. The pollution load from
livestock has increased by about 25%, while the domestic pollution load has minimal changes.
Nutrient inflows from agriculture, forest areas or as a result of erosion are relatively unimportant
for the process of eutrophication and have not been elaborated in detail. Nevertheless,
interventions in these sectors may contribute to the preservation of the Lake Toba area and
some suggestions about this are presented in section N.
In addition to phosphorous and nitrogen, other parameters are important for eutrophication,
such as biochemical oxygen demand (BOD). Subsequent more detailed studies on water
quality in Lake Toba would need to consider this as well. Apart from eutrophication, other
parameters may have locally important impacts on water quality and even human health, such
as inorganic compounds, pesticides and pathogens. These are among the variables suggested
for intensive monitoring in section 9.3.
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6 State and Impact: Lake Assessment
6.1 Approach
The method applied is a water quality system analysis which encompasses the understanding
of the water quality issues and the underlying causes or drivers. Key components of the water
quality system analysis are:
• Existing knowledge of the hydrology of the Lake Toba Asahan basin as modelled in the Basin Water Resources Management Planning (BWRMP) project (Vernimmen, 2015);
• Existing water quality data of Lake Toba (in collaboration with LIPI, DLH-SU and PTAN); and
• Point and non-point sources of pollution and their emissions, such as domestic emissions, deforestation, industrial development, poor sanitation and unregulated aquaculture;
• Calculations of the pollution loads into Lake Toba;
• Review and assessment of the resulting nutrient concentrations in Lake Toba and identify assumptions and uncertainties therein; and
• Evaluation of development scenarios in relation to the equilibrium pollutant concentration.
The most important aspect of lake water quality is the amount of biological nutrients that are
dissolved in the lake, the so-called eutrophic state. In contrast to other pollutants, continuous
pollution with nutrients (‘eutrophication’ by phosphorous and nitrogen) has the potential to
irreversibly upset the lake chemistry and biology on a system level. Whereas other types of
pollution such as pesticides and pathogens (such as E.coli) will degrade or dilute quickly upon
emission and do not amplify processes that can cause irreversible functional degradation on a
system level. Therefore, this assessment focuses on eutrophication related pollution, more
specifically phosphorous (P) and nitrogen (N) loads. Nutrient concentrations may vary dependent on the specific P-loads or N-loads from the upstream part of the river basin and the predominant circulation patterns. In close communication with LIPI, the assessment was thus carried out for various (sub) compartments (section 2.2.6):
• Whole lake (1 compartment)
• North and south lakes (2 compartments),
• North and 3 south lakes (4 compartments), and
• Other simulations to illustrate the implications of zonation.
Based on this zonation into compartments the changes in estimated concentrations were
compared and evaluated between the whole lake approach and a compartmental approach.
6.2 Available data
6.2.1 Main data sets
Many stakeholders possess or collect data relevant for the study, such as catchment-wide GIS
data on land use, population statistics, agricultural statistics or lake monitoring data such as
nutrient concentrations, water transparency and chlorophyll concentrations. In total 16
stakeholders have been identified, who could contribute data (Annex K.1). All stakeholders had
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different forms of access to, and needs for, these data, and therefore apply different monitoring
approaches. The types of data vary widely, from spatial (GIS) data to single water quality
parameters and can be divided into three functional categories: (1) signal function; (2)
exploratory data; (3) statistically conclusive.
Three data sources provided data for the water quality assessment: the Provincial Environment
Agency (DLH-SU), the Indonesian Institute of Science (LIPI), and PT Aquafarm Nusantara
(PTAN). An outline of these three datasets is provided in section 3.3. The initial purpose of the
datasets differs and so does the monitoring design. DLH-SU aims at the determination of lake
status (level 1, signal function). LIPI seeks to understand the system, aiming for levels 2
(exploratory) to 3 (scientific). PTAN needs the data for ASC certification, for which it needs to
understand the effect of aquaculture on the environment in which it is situated (system
knowledge). This means at least level 2, but only for a part of the lake system. The available
data sets have been compared to standard monitoring guidelines in Annex K.2.
Remote sensing was also used to illustrate the application of methods for measuring water
quality. Conventional in situ water quality sampling limited to a local scale can be costly and
labor intensive, whereas remote sensing can increase data availability by providing two-
dimensional maps derived through various inversion methods that would otherwise require a
large number of in situ water quality monitoring stations. Typically the application of proposed
remote sensing methods are supporting quantitative assessments of location, timing and
phasing of treatment infrastructure, a rationale for establishing priorities for water pollution
control interventions to improve environmental quality, and ultimately the development of
integrated pollution management and monitoring solutions that are financially, socially,
economically and environmentally sustainable, as well as the definition of a process for
prioritizing investment opportunities and trade-offs of the different options considered. Specific
objectives associated with appplication of the remote sensing tools included:
• An assessment on the feasibility of integrated modeling-remote sensing methods
towards integrated approaches of water quality monitoring in surface water bodies.
• A description of next steps in capacity strengthening activities on the use of water
quality modeling and remote sensing tools towards integrated approaches of water
quality monitoring.
6.2.2 Quality of data
Each data set is specific in its spatial and temporal distribution (Annex J.3). Information about
quality control of the monitoring data was only available from the literature and personal
communication. This has revealed that both LIPI and DLH use government labs (Pusarpedal
KLHK) and perform regular quality tests of their equipment. PTAN uses on-site labs and these
are periodically quality-checked by Wageningen University and Research in the Netherlands.
While this is not an official certification, it is sufficient for PTAN to comply with ASC standards
(section 3.2.2).
The most important aspect in quality of water sample analysis is the consistency of the
laboratory chosen (section 9.1.6). This allows for comparison between samples over time.
However, when a switch is made to a different laboratory, monitored concentrations are known
to change so it is highly recommended to keep the same laboratory involved throughout the
monitoring efforts.
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6.3 Physical and chemical parameters
Below, an overview is presented of the present state of water quality variables, and how they have developed over the past 10 years. The assessment below is mainly based on the PTAN data since it constitutes the data set with the highest sampling frequency. Other data sources (BLU-SU and LIPI) are selectively included to complement these data and/or give an impression of the level of agreement between data sets.
Multispectral remote sensing using publicly available earth-observation satellite data was
analysed to provide unique insight into the complex water-quality dynamics of Lake Toba.
Multiple sensors are needed since temporal coverage is limited by atmospheric conditions and
overpass schedule (LS8 / S2A ‘land’ sensors: 5~10 days; S3A: ~1day but lower spatial
resolution), with additional sensors projected to be available in the near future. A summary of
the sensors used and their key characteristics is provided inTable 6.1, and illustrated inFigure
6.1. These were used to carry out the following: • Time-series estimates of turbidity, chlorophyll and vegetative cover were derived
from Sentinel-2A, Landsat-8, MERIS, MODIS, Landsat- 5/7 • Long-term changes in water quality (MERIS time-series ~2006) across the lake,
and specific changes in land-use in the Aek Manira watershed were observed. • Possible contributors to a significant water-quality event on January 9th, 2017 in
Bakara / Baktiraja region were discovered and described • possible approaches to overcome challenges related to data quality & quantity due
to atmospheric conditions were demonstrated: (i) marine layer-cloud-glint masks; (ii) combination of water quality products from multiple sensors
• ability to obtain multi-spectral imagery and water-quality dynamics on short time-scales (daily / intra-day) using geostationary platform (e.g. Himawari-8) was demonstrated
• remote-sensing data access, sources, processing algorithms and future work towards a comprehensive monitoring strategy were documented.
Table 6.1. High-resolution multi-spectral instruments supplemented with other atmospheric / land / OC missions
used in the Lake Toba study.
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Figure 6.1, Illustration of the combination of sensors and analysis used to gain an integral understanding of water
quality dynamics in Lake Toba and its basin.
6.3.1 Temperature
Water temperature is one of the variables that determine the depth of the thermocline that in turn sets the boundary of the mixing layers in the lake (section 6.6). The water temperature varies between 25 and 28 degrees Celsius (Figure 6.2 and Figure 6.3) and has been stable for the last 10 years. A minor increase is seen in the beginning of 2016, when surface water temperatures peaked at over 28 degrees Celsius. Each PTAN station showed a similar trend and values.
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Figure 6.2, Temperature (in degrees Celsius) measured at 2 m depth at the four PTAN locations. (Figure provided
by PTAN, 2017. See Figure 3.5 for legend and location of the sites.)
Figure 6.3, Temperatures measured in April and October along a depth profile of 100 meters, as measured at
stations 2, 5, 7, 11, and 12 (figure provided by LIPI).
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Figure 6.4, Oxygen dynamics along depth profiles (in m below the surface) sampled on a monthly basis from 2008
to 2016 at field station Pangambatan (NGB). (Figure provided by PTAN, 2017)
Figure 6.5, Temperature dynamics along depth profiles sampled on a monthly basis from 2008 to 2016 at field
station Pangambatan (NGB). (Figure provided by PTAN, 2017)
6.3.2 Dissolved Oxygen (DO)
Levels of dissolved oxygen (DO in mg/l) show different values and trends for stations near fish farms in comparison with the control (Figure 6.6). Measurements at fish farm locations have lower DO levels and fluctuate within and between years. Control measurements show a peak in 2006, 2007 and again in 2016, but otherwise values are stable. DO values steadily decline as depth increases and level out after 200 meters (Figure 6.7).
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Figure 6.6, Dissolved oxygen (mg/l) measured at 2 m depth at the four PTAN locations. Figure provided by PTAN,
2017. See Figure 3.5 for legend and location of the sites.
Figure 6.7, Dissolved oxygen profiles (in mg/l) measured at the four PTAN locations (Figure provided by PTAN,
2017).
The LIPI depth profile measurements show similar values to PTAN (Figure 6.8). An interesting anomaly is seen at station 11, in the middle of the southern part of the lake. At around 200 meters depth there is a sudden increase in oxygen value. This increase is not shown at any of the other points and could be caused by very local nearby thermal vents, or it could be the result of measurement errors.
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Figure 6.8, Dissolved oxygen (mg/l) along a depth profile of 400 meters, measured at stations 2, 5, 7, 11, and 12, in
April (left) and October (right) 2009 (Figure provided by LIPI).
6.3.3 Transparency (Secchi depth)
Data from all field stations show a similar trend reaching highest values between 2009 and 2010, with a sudden and drastic decrease in 2016 (see section 6.9.2). After 2016 transparency reaches its initial value of around 6m depth (Figure 6.9), corresponding to an ultra-oligotrophic lake according to the classification of Chapman (1996). Secchi disk depth is almost always deeper at the control station. There are events during which visibility is above 10m. This is very rare for any type of lake. Such rare events would disqualify Lake Toba for ASC certification (see section 3.2.2).
Figure 6.9, Secchi depth (in m) measured at the four PTAN locations. (Figure provided by PTAN, 2017. See Figure
3.5 for legend and location of the sites.)
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6.4 Nutrients
6.4.1 Phosphorous
From 2006, when the measurements started, to 2012, phosphorous concentrations were low
(around 0.01 mg/l) with some occasional peaks especially at field station TMK, which was
closed in 2008. These values, presented in Figure 6.10 and Figure 6.11, seem to increase from
2012 onwards, with highest values measured in 2016, in roughly the same months as the other
anomalies (section 6.9.2). Analysis of the BHL-SU data shows that the temporal variation in
total phosphorous (TP) is higher than the spatial variation. Therefore, the average TP
measurements per moment were taken and plotted over time (Figure 6.12). The figure shows
that TP concentrations are mainly below 0.04 mg/l which is in line with the PTAN data for this
period. However, the BHL-SU data show a peak in 2014, at which moment they reach levels
clearly higher than those in the PTAN data (Figure 6.11).
Figure 6.10, Dissolved phosphorous concentration (mg/l) measured at the four PTAN locations over the period
2006-2017. (Figure provided by PTAN, 2017. See Figure 3.5 for legend and location of the sites.)
Figure 6.11, Total phosphorous concentration (in mg/l) measured at the four PTAN locations. (Figure provided by
PTAN, 2017. See Figure 3.5 for legend and location of the sites.)
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Figure 6.12, DLH-SU data on total phosphorous, averaged over all locations throughout Lake Toba in 1996, 2012,
2013, 2014 and 2016. Numbers at the bottom of each bar indicate the number of locations sampled (source:
DLU-SU).
The LIPI data set shows that TP concentrations measured in 2013 vary between 0.012 and 0.041 µg/l, which corresponds well with the previous figures. Station 7 and 8 (with concentrations of 0.019 and 0.015 µg/l) are those closest to the measuring points of PTAN. In the period from 2008 to 2012 the trophic state of the measuring locations is oligotrophic. From 2012 up to the end of 2016 the values correspond to a mesotrophic state.
A study conducted by LIPI in 2010 describes the trophic state of 19 different measuring points
along the coastline of Lake Toba. The state is determined by the values of a series of
parameters measured (Annex J.5). The LIPI findings correspond well with the PTAN figures.
6.4.2 Nitrogen
Total ammonia values at the PTAN control station seem fairly constant. Besides the minor
peaks in 2008, 2011 and 2014, control values are lower than values at fish farm stations (Figure
6.13). Total nitrogen (TN) values are lowest between 2009 and 2014. Measured TN
concentrations do not show a difference between control and fish farm stations. Measured TN
concentrations at the field stations mainly correspond to an oligotrophic state, as they are mostly below the most conservative threshold of 350 μg/l (KLH, 2009), and only very
occasionally exceed the most lenient threshold of 650 μg/l.
In 2013 LIPI conducted another assessment of water quality parameters. As in 2010 they
sampled 19 sites for different parameters. Only total nitrogen (TN) was measured in both years
(Figure 6.14). In 2013 TN was on average lower than in 2010. However, in view of the large
within-year variation (Figure 6.13) this cannot be interpreted in terms of trending. The LIPI 2013
data set shows that TN concentrations measured in 2013 vary between 0.075 and 0.374 mg/l,
which corresponds well with the above figures (see also Annex J.5).
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Figure 6.13, Total dissolved nitrogen (in mg/l) concentrations measured at the four PTAN locations. (Figure
provided by PTAN, 2017. See Figure 3.5 for legend and location of the sites.)
Figure 6.14, Total nitrogen concentrations measured at the four PTAN locations. (Figure provided by PTAN, 2017.
See Figure 3.5 for legend and location of the sites.)
6.5 Organic content Chlorophyll α concentration and dry weight show similar trends at all stations (Figure 6.15 and Figure 6.16). Chlorophyll α values show little difference between stations and all show a sudden peak in 2016. Dry weight values show the same trend, except in this case the values for the control station are lower compared to fish farm stations. Till the end of 2014, chlorophyll concentrations are within the class limit of ultra-oligotrophic lakes. During the period Feb-Aug 2016 however, chlorophyll concentrations rose to12 µg/l and the lake fell within the mesotrophic class (section 5.3).
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Figure 6.15, Chlorophyll concentration (in microgram/l) measured at the four PTAN locations. (Figure provided by
PTAN, 2017. See Figure 3.5 for legend and location of the sites.)
Figure 6.16, Dry weight (in mg/l) measured at the four PTAN locations between 2006 and 2017. (Figure provided by
PTAN, 2017. See Figure 3.5 for legend and location of the sites.)
6.6 Thermocline depth
The thermocline depth has a two-fold importance with respect to eutrophication. Firstly, it
determines the volume over which the incoming nutrients are diluted. The deeper the
thermocline, the more volume, and the lower the concentrations are. Secondly, it determines
whether an algal bloom may occur or not (see also section 2.2.5 and Annex C.2). The depth of
the thermocline in Lake Toba was determined with a simple 1Dv Delft3D-WAQ model assuming
the mixed layer to be fully mixed and a background extinction rate of 0.4 (which corresponds
to a Secchi depth of ~5m). Also, initial TN=0.2 mg/l and TP=0.02 mg/l. The relation between
thermocline depth and chlorophyll concentration resulting from the 1Dv model is shown in
Figure 6.17. The different lines correspond to different thermocline depths, or sequences
thereof: 60_30_20 means that the thermocline depth starts at 60m, but is changed at day 211
to 30m and at day 241 to 20m. The days at which the changes in thermocline depths occur are
fixed.
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Figure 6.17, Chlorophyll concentrations (µg/l) over time (in days) when the thermocline depth is assumed to occur
instantly, or achieved stepwise over time (e.g. from 20 to 30 and 60 meters).
The model results show that the maximum chlorophyll concentrations depend on whether the
thermocline depth is assumed to occur instantly, or whether it is achieved stepwise in time. For
example, when the thermocline depth changes instantly from 60m to 20m, chlorophyll
concentrations reach a peak value of 25 µg/l. However, if they change stepwise from 60m via
30m to 20m, the maximum chlorophyll concentration predicted by the model is 12 µg/l. This is
because algal growth and sedimentation may affect the loss of nutrients from the epilimnion,
and therefore changes the nutrient availability over time.
This analysis suggests that the default thermocline depth in Lake Toba lies around 50m, since
at this depth the modelled chlorophyll concentrations match best with observed chlorophyll
concentrations (Figure 6.15). This depth seems to be in line with the various observed
stratification profiles (e.g. Figure 6.6). A sensitivity analysis of the thermocline depth showed
that P concentrations lowered from about 60 µg/l at 20m thermocline depth to about 20 µg/l at
60m thermocline depth. Ultimately, 50m was selected based on all analyses combined.
According to the results of the 1Dv model, the thermocline depth in 2016 probably decreased
to a depth of 30m or (in a more stepwise manner) to 20m, since at these depths the modelled
chlorophyll matches best with the observed chlorophyll peak (Figure 6.15). Note that this
change in thermocline depth probably corresponds to a change in (or occurrence of the)
secondary thermocline, since the observed 25 °C level (~primary thermocline) is not shifted to
shallower depths (Figure 6.5).
6.7 Remote sensing insights into water quality dynamics
The remote sensing-based analysis of Lake Toba suggested the presence of complex water-
quality dynamics driven by nutrient-oxygen-light mixing. Although Lake Toba is a large and
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deep water mass, surface mixing appears to be driven by hydrologic transport (i.e., in-flow /
outflow).
Evidence of natural and cultural eutrophication is apparent in long-term (MERIS) time-series
data starting around 2006. An approximately two-fold increase in regionally-averaged
Chlorophyll-a from 1~2 mg/m3 to 2~6 mg/m3 and corresponding two-fold increase in light
attenuation at 490nm (turbidity) were observed. In localized areas, the maximum biological
productivity is much higher.
Mesotrophic to eutrophic lake conditions with Chlorophyll-a concentrations of 4 ~ 30 mg/m3
were also derived from Landsat-8 / Sentinel-2A imagery with complex local variability. To
improve the quality of data retrievals, cloud-glint data masking refinements and further regional
tuning are required. Additionally, the long term MERIS time-series and imagery as well as high-
resolution (Sentinel-2A / Landsat-8) imagery show a significant increase in variability (temporal
and spatial) for both chlorophyll / turbidity (Figure 6.18).
Time-series for broad regional segments of Lake Toba show a eutrophic condition of broad
regional segments (period 2013~present) with high level of spatial and temporal variability.
Broad lake aerial binning shows seasonal variability and an increase in Chlorophyll-a and
turbidity by a factor of 2 starting in mid 2005 ~ 2006. The rate of change and variability in
Chlorophyll-a and turbidity also increases during the period between 2006 and 2012 compared
to 2002 to 2005.
Figure 6.18, Ilustration of MERIS example images and time series of Turbidity and Chlorophyll-a for different parts
of Lake Toba.
The impacts of pollution events can also be captured through remote sensing observations. A
water-quality event on January 9th 2017 in the SE of Lake Toba in Bakara /Baktiraja region,
which led to hypoxia and aquaculture loss, is visible in RGB images from space using Landsat-
8, Himawari-8 and Sentinel-3A (VIIRS not verified), as depicted in Figure 6.19. Chlorophyll-a
levels reaching > 10mg/m3 (>30 locally) and evidence of benthic sediment re-suspension
(Figure 5-4) can possibly be explained by significant precipitation and discharge from Aek
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Manira/Silang. Reported meteorological conditions preceding significant precipitation event are
not available, but meteorology visible from Himawari-8 during first week of January. Himawari-
8 observation on Jan 10th shows significantly reduced HAB biological activity, which appears
well correlated with the dissolved oxygen measurements reported at sub 1ppm level (common
threshold supporting biological processes).
Figure 6.19, Illustration event of the Hypoxia and Harmful Algal Bloom (HAB) that occurred on January 9th of 2017,
resulting in hundreds of tons of dead fish in Lake Toba, and the satellite derived images of chlorophyll-a and
total suspended matter.
6.8 Hydrothermal stability and mixing events
Mixing events may have a large impact on the biogeochemistry of the lake (see section 2.2.6).
A brief analysis into the hydrothermal status of the lake has been carried out to explain the
patterns as observed in the temperature and oxygen profile measured over 9 years (from Feb
2008 until Feb 2017) at the PTAN field station Pangambattan located in the narrow passage,
east of Samosir peninsula (Figure 6.5, modified in Figure 6.20). White vertical lines show
instances when the anoxic level is shallow and black lines when it is deep. These instances
coincide with periods of thermal stratification, when the surface water is warm and with periods
of deeper mixing with cooler surface water, respectively. The analysis below is specifically
aimed at understanding the decrease in depth of anoxic water in the period February to August
2016.
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Figure 6.20, Oxygen and temperature dynamics Lake Toba 2008-2017 (after PTAN 2017).
Very little information on the hydrothermal status of and meteorology above Lake Toba is found
in the literature. Yet, Sene et al. (1991) provide some insight into the typical conditions for wind,
air temperature, and humidity over a short period of 42 days in January and February 1989
near Pulo Tao island (1 km north of Samosir, the large central peninsula). From this reference
meteorological observations in the period 2003-2010 were adjusted and the air temperature
was reduced by 3°C accordingly. Figure 6.21 shows the 1DV simulations based on the same
methodology as the 3D hydrodynamic and transport code Delft3D-FLOW of Deltares (Deltares,
2014). In Figure 6.21 the upper panel shows the applied air temperature (black line) and the
simulated surface water temperature (red line) and in the central panel the applied wind
magnitude. The lower panel in Figure 6.20 shows the temperature in the top 100m of the 505m
deep model. From Figure 6.21 it appears that Lake Toba develops a thermocline (warmer top
layer) of marginal stability i.e. with instances of mixing to depths of about 50m. These instances
appear to be bi-annual notably due to the wind of the monsoon cycles.
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Figure 6.21, 1DV run based on Delft3D-FLOW code for Lake Toba with 100 non-equidistant layers over its
maximum 505m depth (upper 100m shown) and meteorological forcing from National University of
Singapore from 2003-2010 and with air temperature reduced by 3 °C, in agreement with Sene et al., 1991.
Top panel: air temperature (black) and surface water temperature (red). Central panel: wind magnitude with
bi-annual increase in wind speed. Lower panel: stratification in water temperature with bi-annual periods
with deeper mixing due increased wind speed.
Patterns in the observed water temperature (Figure 6.20) suggest bi-annual mixing and re-
stratification events in the upper 10-20m in most of the years. The mixing events do not create
deep mixing (i.e. surface water is not mixed downward beyond 50m depth). The latter can be
understood by the reported mild wind pattern e.g. in Sene et al., 1991. Equal patterns in terms
of patterns rather than in precise temperatures can be found in the 1DV simulations (Figure
6.21).
It is this absence of deep(er) mixing that creates the permanent anoxic condition beyond 150m
depths shown in Figure 6.20. In periods of thermal stratification (warm surface water, red
coloured) the upper level of anoxic water rises to shallower depths (black lines in Figure 6.20).
In periods of deep mixing (cooler surface water, green coloured) the upper level of anoxic water
descends to greater depths (white lines in Figure 6.20). The rising of the upper level of anoxic
water appears not to be due to some strong upwelling events, since the observed 25 °C level
is not equally shifted upward with the DO isoline. Therefore, these coincidences are interpreted
as oxygen-rich water being mixed downward from the water surface, or (given some oxygen
consumption) oxygen-depleted water being created in the absence of vertical mixing.
In addition to the Feb-Aug 2016 event with the decreasing depth of anoxic water (more on this
anomaly in section 6.9.2), Figure 6.20 shows some instances with deep cooler water (blue
colour: 24°C). However, these cooler waters do not extend to the water surface. Hence, local
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cooling of the water surface and downward mixing is not the source of this 24°C cooler deep
water. More likely upwelling events from the deeper parts of Lake Toba bring cooler water from
larger depths up into the narrow passage east of the peninsula. Given the size of Lake Toba
north and south basins as well as the temperature stratification, the period of the internal
seiches ranges from 2-4 days. These events appear too short to be visualized in Figure 6.20
unless the sampling period of temperature is long relative to this monthly or other short-term
period and the interpolation of the plotting code artificially widens the cold periods.
If the upwelling events (and the subsequent period with deep cooler water) are not explained
by downward mixing or by internal seiches, what may then be causing them? One option is
some rare stormy event that creates very deep mixing elsewhere in Lake Toba down to depths
exceeding 200m. Temperature and wind speed records do not suggest particular windy or hot
events in February 2016 that would explain the longer temperature stratification and/or anoxic
depth levels (Figure 6.22). Alternatively, it may be caused by cooler (river) inflow which sinks
to larger depths, as is the fate of the cold Rhone River flow into Lake Geneva. Yet another
option is sub-aquatic sources of cooler water, such as are present in Lake Kivu, Rwanda (Ross
et al., 2015).
Figure 6.22, Temperature and wind speed recorded at Medan Airport 80 km North of Lake Toba.
In this brief analysis it is concluded that wind may lead to bi-annual mixing and re-stratification
events in the upper 10-20m in most of the years. Deep mixing does, however, not occur, which
explains the anoxia in the deep layers. Also, some upwelling of cooler water from the deep
occurs. But these cooler waters do not extend to the water surface (at least not in the observed
period). The February to August 2016 event with the decreasing depth of anoxic water seems
to be explained by long cloudless weather conditions during that period. The resulting long and
strong (secondary) temperature stratification in this period is probably the cause of an
exceptionally strong algal bloom (which was indeed recorded by PTAN, see Figure 6.15)
creating high concentrations of detritus and correspondingly large oxygen consumption.
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6.9 Trends
6.9.1 Present data vs historical data
The large volume of Lake Toba may buffer any nutrient input and shield the system from direct
effects (see section 2.2). As a result, changes only become visible when assessed over large
periods of time. In the first half of the previous century Ruttner (1931) conducted a series of
water quality measurements (Table 6.2). In this period the areas surrounding Lake Toba were
not yet affected by aquaculture, agriculture or forestry. In his study Ruttner made a division
between the northern and southern basin of the lake and he was also able to make a depth
profile for oxygen and dissolved phosphates. • Compared to the TP concentrations measured by Ruttner of 0.005 mg/l (in 1930; Ruttner,
1931), orthophosphates as measured by PTAN in 2013 (Figure 6.10) have doubled to 0.01 PO4-P (mg/l), and during the peak in 2016 they even show a tenfold increase to 0.05 PO4-P (mg/l).
• Also at greater water depths phosphorous concentrations are increasing. In 1930 concentrations at 150m depth were measured to be 0.012-0.18 PO4-P (mg/l), whereas in 2013 these values have (more than) doubled to 0.04 PO4-P (mg/l).
• With respect to oxygen, surface water concentrations at PTAN stations (Figure 6.6) seem to have remained constant over the last 90 years. At depths greater than 150 meter however, all DO values between 2008 and 2017 are below 0.5 mg/l (Figure 6.7), which is clearly lower than the values reported by Ruttner and which ranged between 5.35-5.40 mg/l. Potential causes for this difference are discussed in the next chapter.
• Transparency in the 1930’s ranged between 7.5-11.5m, above the limits for ASC certification. Current Secchi disk measurements fluctuate around 6 meters (Figure 6.9), showing a decrease in the average visibility depth of at least 1.5m.
The above comparison of current data to historical measurement clearly suggests that water quality in the lake has decreased since 1930, both at the surface and at greater depths. This may entail some risks as was discussed in section 2.2.6.
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Table 6.2 Values of water quality parameters in 1930 (Ruttner, 1931).
North basin South basin
Temperature (C°) 25.45-26.4 25.45-26.4
Transparency (m) 7.5-11.5 8.0-11.5
Dissolved O2 (mg/l) 7.0-7.6 7.0-7.6
Ortho PO4-P (mg/l) 0.005 0.005
Total PO4-P (mg/l) - -
Total N (mg/l) - -
O2 (mg/l)
Depth (m)
0 7.4 7.56
50 5.35 5.4
100 5.37 2.74
150 4.07 1.54
200 - 1.53
PO4-P (mg/l) Depth (m)
0 0.005 0.005
50 0.005 0.005
100 0.008 0.01
150 0.012 0.018
200 - 0.2
6.9.2 The 2016 anomaly
At the beginning of 2016, all measurements show extreme values. There is an increase in
temperature at the water surface (Figure 6.2) and water temperature (Figure 6.5). This
coincides with a remarkable drop in dissolved oxygen at shallower depth in the period February
to August 2016 (Figure 6.4) (less visible at 2m depth in Figure 6.6). This coincides with other
phenomena, such as the preceding drop in Secchi depth (Figure 6.9) as well as phosphorous
(Figure 6.10 and Figure 6.11). There was a similar sudden peak in chlorophyll concentration
(Figure 6.15) up to 12 µg/l and dry weight (Figure 6.16). This suggests that there was an algal
bloom at that moment and during this period the lake entered the mesotrophic class. The
subsequent increase in visibility to levels above 6m (Figure 6.9) cannot be explained easily.
The anomaly is also visible as a thermal stratification event in the period February – August
2016 (Figure 6.20). This event shows the same pattern as the other thermal stratification
events, but in 2016 the rising of the upper level of anoxic water is particularly strong. What
could have caused this? Temperature and wind speed recorded at Medan Airport 80 km north
of Lake Toba do not suggest particular windy or hot events in Feb 2016 (Figure 6.22). However,
these measurements may not be fully representative for the Lake Toba area as this period was
reported to be (at least locally) particularly cloudless17. This cloudless period could explain the
relatively long and strong (secondary) temperature stratification in this period. This, in turn, may
have caused an exceptionally strong algal bloom (which was indeed recorded by PTAN, see
17 Based on personal observations by JanJaap Brinkman. As the meteorological station is far from Lake Toba, hard
evidence on cloud cover is not available.
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Figure 6.15) creating high concentrations of detritus and correspondingly large oxygen
consumption. However, other causes may have influenced the temporary rising of anoxic water
as well.
6.10 Lake status
The most important determinant of lake water quality is the amount of dissolved nutrients; this
is known as the ’trophic state’. Table 6.3 lists the generally accepted classifications for eutrophic
state. In contrast to other pollutants, continuous nutrient pollution from phosphorous and
nitrogen, ‘eutrophication’, has the potential to irreversibly affect lake chemistry and biology on
a system level. Pollution from as pesticides and pathogens, e.g. E. coli, quickly degrade or
dilute and do not amplify processes that cause irreversible functional system level degradation.
Water transparency, organic content, e.g. chlorophyll-a, phosphorous, and nitrogen are are key
water quality parameters that determine the lake trophic state.
Table 6.3, Overview of types of lake status (Chapman, 1996).
Laks status Description
Oligotrophic
lakes
Lakes of low primary productivity and low biomass associated with low concentrations
of nutrients (N and P). These lakes tend to be saturated with Oxygen (O2) throughout
the water column.
Mesotrophic
lakes
These lakes are less well defined than either oligotrophic or eutrophic lakes and are
generally thought to be lakes in transition between the two conditions. Some
depression in oxygen (O2) concentrations occurs in the lower water layer
(hypolimnion).
Eutrophic lakes Lakes that display high concentrations of nutrients and an associated high biomass
production, usually with a low transparency. Water use may become limited. Oxygen
concentrations can get very low, often less than 1 mg/l in the hypolimnion during
stratification.
Hypereutrophic
lakes
Lakes at the extreme end of the eutrophic range with exceedingly high nutrient
concentrations and associated biomass production. The use of the water is severely
impaired. Anoxia or complete loss of oxygen often occurs in the hypolimnion during
stratification.
Based on available data from monitoring sites scattered along shorelines, observed values in
Lake Toba show mesotrophic status for phosphorous and oxygen profiles while nitrogen,
chlorophyll α and transparency point to oligotrophic status but occasionally reach the
mesotrophic (Table 6.4).
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Table 6.4, Overview of present status of selected water quality parameters at Lake Toba (based on data from DLH-
SU, LIPI, and PTAN).
Parameter Conditions at Lake Toba
Phosphorous
In the period from 2008 to 2012 the trophic state of the measuring locations is oligotrophic for
phosphorous. From 2012 untill the end of 2016 the phosphorous values correspond to a
mesotrophic state.
Nitrogen The measured total nitrogen concentrations at field stations correspond largely to an
oligotrophic state, as they are mostly below the most conservative threshold of 350 μg/l, and
only very occasionally exceed the most lenient threshold of 650 μg/l.
Chlorophyll α Chlorophyll α values show little difference between stations and all show a sudden peak in
2016. Till the end of 2014, chlorophyll concentrations are within the class limit of ultra-
oliogotrophic lakes. During the period Feb-Aug 2016 however, chlorophyll concentrations rise
to 12 µg/l, thereby reaching the mesotrophic class.
Transparency Water transparency (ecchi depth) data from all field stations show a similar trend, reaching
highest values between 2009 and 2010, with a sudden and drastic decrease in 2016 related
to the algal bloom occurring at that moment. After 2016 transparency reaches its initial value
of around 6 meter depth corresponding to an oligotrophic lake according to the classification
of Chapman (1996). There are events during which transparency is above 10 meter depth,
very rare for any type of lake.
Temperature Temperature at water surface varies between 25 and 28 degrees Celsius and has been stable
for the last 10 years. A minor increase is seen in the beginning of 2016, when surface water
temperatures peaks over 28 degrees Celsius. Each PTAN station shows similar trend and
values. Temperature profiles show clear stratification.
Oxygen Levels of dissolved oxygen (DO in mg/l) steadily decline as depth increases and remain the
same beyond 200 meters. Peaks occur in 2006, 2007 and again in 2016, but otherwise values
are stable. One exception is a rise to the surface of anoxic water in the period Feb-Aug 2016.
Stations near fish farms show different values and trends than elsewhere in the lake. Fish farm
locations have lower DO levels and fluctuate within and between years. An interesting
anomaly is seen at one measuring station, where the oxygen value suddenly increases at
around 200 meters depth. This could be caused by nearby thermal vents or be the result of
measurement errors.
The long-term trend gives information on possible “nutrient loading” of the lake, which ultimately
can lead to a change of status. In the first half of the previous century Ruttner (1931) conducted
a series of water quality measurements. In this period, the areas surrounding Lake Toba were
not yet affected by aquaculture, agriculture or forestry. The comparison of current data to these
historical measurements clearly suggests that the water quality in the lake has decreased since
1930, both at the surface and at greater depths (Table 6.5).
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Table 6.5, Trends in water quality of Lake Toba, comparing historical data with present day values.
Parameter Trend at Lake Toba
Phosphorous Compared to the phosphorous concentrations measured by Ruttner of 0.005 mg/l (1931),
the concentrations as measured by PTAN in 2013 have doubled to 0.01 PO4-P (mg/l) and
during the peak in 2016 they even show a tenfold increase to 0.05 PO4-P (mg/l). Also at
greater water depths phosphorous concentrations are increasing. In 1930 concentrations
at 150 meters depth were measured to be 0.012-0.18 PO4-P (mg/l), whereas in 2013
these values had (more than) doubled to 0.04 PO4-P (mg/l).
Transparency Transparency in the 1930’s ranged between 7.5-11.5 meters. Current transparency
(Secchi disk) measurements fluctuate around 6 meters, thus showing a decrease in the
average visibility depth of 1.5 meter.
Oxygen With respect to oxygen, surface water concentrations at PTAN stations seem to have
remained constant over the last 90 years. At depths greater than 150 meter however, all
DO values between 2008 and 2017 show values below 0.5mg/l, which is clearly lower
than the values between 5.35-5.40 mg/l as reported by Ruttner.
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7 Future Pressures and Future State
7.1 Approach
The existing Sumatra Spatial Model (Indra Karya, 2015) has been applied to analyse the Lake
Toba catchment area (section 5.1).
7.2 Input data
These are the input data for the scenarios at Lake Toba:
• Administrative units for 2010: Island; Provinces; Districts; Sub-districts; and Villages. Available as ESRI Shape files from BPS
• Drivers o Population growth scenario (BPS extended) o Economic growth scenario (historic trend data from BPS) o Rice / Palawija / Vegetable production and consumption 2010 data by plus
scenario by district (BPS)
• Unit load scenario for water demand, BOD waste load emissions
• Initial situation data for 2010 (population census year) o Population, households and employment by village from BPS o Land use:
▪ Rupa Bumi Indonesia (BIG), often outdated; needed improvement ▪ Peta Audit Baku Sawah from Ministry of Agriculture (paddy field map)
o Gross Regional Product (GRP) by district and sector from BPS o Province level spatial plans (district level not available) from Bappeda/PU Tata
Ruang o Road development plans
7.2.1 Population and economic growth drivers
Population data in the spatial model are taken by villages (desa) from the 2010 population
census from the Statistical Bureau BPS. This is considered the most reliable and consistent
data source for population in Indonesia. Population projections have been made by BPS per
province from the period 2010-2035. These were used as the basis for Figure 7.1 that shows
the annual multiplier for population growth per 5-year period.
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Figure 7.1, Sumatra population growth history and projection (up to 2035 BPS, remainder of SSM).
Economic growth data per province are available from BPS for the period 2000-2013. At the
level of Indonesia the economic growth has been on average 5% for the last 50 years (BPS).
These data provided the basis for a long-term growth scenario, visualised in Figure 7.2, in close
cooperation with the Ministry of PUPR in Sumatra Water Resources Strategic Study (Indra
Karya, 2015).
1971 1 980 1 990 1 995 2 000 2010 2015 2020 2025 2030 2035 2040 2045 2050
Annual multiplier 1.0613 1.0544 1.0226 1.0119 1.0327 1.0168 1.0143 1.0117 1.0095 1.0077 1.0066 1.0056 1.0046
Sumatra 20,808 28,016 36,506 40,830 43,309 5.1E+07 5.5E+07 5.9E+07 6.3E+07 6.6E+07 6.9E+07 7.1E+07 7.3E+07 7.5E+07
0.97
0.98
0.99
1
1.01
1.02
1.03
1.04
1.05
1.06
1.07
-
10,000,000
20,000,000
30,000,000
40,000,000
50,000,000
60,000,000
70,000,000
80,000,000
Annual multiplier
Sumatra
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Figure 7.2, Economic growth by province 2000-2013 with average of 3.7%.
7.2.2 Spatial plan
One of the main inputs of the spatial model is the spatial plan (Figure 7.3). This model will
inform which areas are still free for conversion into an urban area. Areas indicated as ‘protected’
cannot easily be changed from one use to another. The provincial spatial plans show that part
of the area around Lake Toba is protected land and should not be converted to urban areas.
This was incorporated into the Sumatra Spatial Model.
0.00
20000.00
40000.00
60000.00
80000.00
100000.00
120000.00
140000.00
160000.00
2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013
11. Aceh
12. Sumatera Utara
13. Sumatera Barat
14. Riau
15. Jambi
16. Sumatera Selatan
17. Bengkulu
18. Lampung
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Figure 7.3, Lake Toba Spatial Plan.
Road development plans are relevant for the spatial model as the increased accessibility
leads to stronger development near planned roads, in particular the toll roads (Figure 7.4).
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Figure 7.4, PUPR Toll Road Development Plan 2009.
7.3 Projections in the Sumatra Spatial Model
The results of the Sumatra Spatial Model for future loads consist of:
• Population and employment projections 2010-2050, and
• Land use change projections 2010-2050
The above projections are available at desa, kecamatan, kabupaten, province, and island level.
With the SSM postprocessor these results are converted to the water districts (Figure 7.5) in
the Lake Toba simulation model. The projection starts with the 2010 population census data.
This is the most reliable population dataset for the intermediary years, but the BPS data on
birth, death and migration statistics are less reliable. Results are analysed for the years 2018,
2022 and 2042 to determine the impact of short term investments over a period of five years
and the long-term impacts after twenty-five years.
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7.3.1 Population projection
Projected population densities in the Lake Toba catchment are visualised in Figure 5.3 for 2018
and in Figure 7.5 for 2042. This includes each desa and keluhahan that drains into Lake Toba.
Subsequently, Figure 7.6 shows the population growth as the difference between projected
populations in 2042 and 2018.
Figure 7.5, Lake Toba catchment population density by desa predicted for 2042 (map provided by Poul Grashoff).
Figure 7.6, Percentage of Lake Toba catchment population growth by desa, 2018-2042 (map provided by Poul
Grashoff).
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Population numbers by water district (and totals by Lake Toba compartment) in combination
with unit waste load data serve to calculate the Lake Toba waste loads. The actual loads to
Lake Toba could be lower due to a reduction of loads during transport in local sewers or via
surface runoff. A correction factor for runoff has been integrated into the model.
7.3.2 Land use change projection
Land use changes are presented here as a proportion of a desa. In other words, it shows how
much of a desa has a certain land use. The waste loads are calculated with most relevant here:
the proportions of urban area, paddy field area and plantations. These are available for each
time step at the desa level. The results have also been converted to water district area forthe
waste load calculation.
For the urban area the results are shown for 2018 and 2042 in Figure 7.7 and Figure 7.8,
respectively. Compared to other regions the Lake Toba catchment area seems less urbanized
(only 4% in 2018) and that will most likely remain so in the near future. Nevertheless, the urban
area grows strongly by about 66% in the Lake Toba catchment area from 2018 to 2042.
Figure 7.7, Urban area fraction by desa in 2018 (map provided by Poul Grashoff).
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Figure 7.8, Urban area fraction by desa in 2042 (map provided by Poul Grashoff).
In terms of land use in the contributing watershed to the lake, a visual analysis of land use in
the Lake Toba catchment from MODIS and Landsat annual products showed limited large-
scale changes in overall vegetative cover observed in the period 2000-2010 (NASA MODIS).
However, pronounced change in land-use is apparent in a localized area SW of Lake Toba
(Aek Manira / Aek Silang aquifer): ~1% reduction in vegetative cover per year in period 2000-
2010 (MODIS PTC) and qualitatively more significant changes in the last 4 years (2013-2017,
Landsat-8 - Figure 7.9).
Figure 7.9, Ilustration of land use change analysis in the Aek Manira/Silang Watershed over the last five years and
the decline of the vegetation cover.
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7.3.3 Tourism
The spatial model does not include tourism as a sector in terms of population. To be able to
include tourism in the waste loads, tourism data were assigned to villages in the Lake Toba
catchment based on the tourism study. That study provided basic data to calculate equivalent
inhabitants and estimation of peak numbers (Table 7.1). These are yearly figures and not all
visitors visit at the same time. However, during the year as well as during the week there will
be peaks in the number of visitors. These peaks are less important in the calculations of
emissions, but crucial in the design of sanitation infrastructure (section 8.4) that will need to be
built for these peak times. To be on the safe side, it is assumed that a maximum of 1/6th of the
total annual number of visitors will be present at the same time (Table 7.1).
Table 7.1, Current and projected number of tourists to Lake Toba (HHTL, 2017).
Business-as-usual scenario Best case scenario
2015 2022 2042 2022 2042
Number of visitors
Domestic 1,743,500 1,978,279 2,219,700 2,125,128 3,128,700
Foreign 58,709 80,408 87,300 86,610 281,600
Total Lake Toba 1,802,209 2,058,686 2,307,000 2,211.739 3,410,300
Average length
of stay (days)
Domestic 2.7 2.6 2.7 2.7 2.6
Foreign 2.1 2.1 2.1 2.1 2.3
Equivalent
inhabitants
13,426 14,816 16,612 16,115 23,930
Peak number of
visitors at one
time
300,368 343,114 384,500 368,623 568,363
Tourism development (planned and unplanned) will take place in certain areas of interest and
attraction. According to ‘Market Analysis and Demand Assessment Lake Toba’ the focus of
future tourism development should be in villages in the following districts: Balige, Girsang
Sipangan Bolon, Simandindo, and Pangururan.
7.4 Nutrient concentration trajectories
Based on the loads calculated in chapter 5, total nitrogen (TN) and total phosphorous (TP)
concentrations were calculated for each of the compartments (see Annex J.4 for details on the
method). The budget model was given parameters as shown in Table 7.2 and Table 7.3. The
thermocline depth was determined on the basis of a simple 1Dv Delft3D-WAQ model (see
section 6.6) at a depth of 50m, and during the Feb-Aug 2016 event at a depth of 20-30m.
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Table 7.2, Properties of the whole lake and two compartments, as assumed in the carrying capacity calculations.
Whole lake 2 compartments
North South
Area (m2) 1,24E+09 6,60E+08 5,84E+08
Average depth (m) 228 206 206
Thermocline depth (m) 20 20 20
Outflow (m3/s) 110 50 110
Volume (m3) 2,84E+11 1,36E+11 1,20E+11
Epilimnion volume (m3) 2,49E+10 1,32E+10 1,17E+10
Table 7.3, Properties of four compartments, as assumed in the carrying capacity calculations
4 compartments
N S1 S2 S3
Area (m2) 6,60E+08 2,78E+07 4,68E+08 8,83E+07
Average depth (m) 90 200 100 80
Thermocline depth (m) 20 20 20 20
Outflow (m3/s) 50 10 110 110
Volume (m3) 5,94E+10 5,56E+09 4,68E+10 7,06E+09
Epilimnion volume (m3) 1,32E+10 5,56E+08 9,35E+09 1,77E+09
The model results were calibrated with the retention rate. The resulting total nitrogen (TN) and
total phosphorous (TP) concentrations match best with the present state when assuming
retention rates of 0.001 and 0.002 for nitrogen (N) and phosphorous (P) respectively. Resulting
TN and TP concentrations and how they depend on the thermocline depth are shown in Figure
7.10.
Obviously, at a smaller thermocline depth nutrients are diluted over a smaller volume which
leads to increased concentrations. At a thermocline depth of 50m (which was set to be the
default depth on the basis of chlorophyll concentrations), total nutrient concentrations averaged
over the whole lake amount to TN=224 µg/l and TP = 26 µg/l. These concentrations both lie
well within the observed ranges of 2015. At a thermocline depth of 20m, nutrient concentrations
increase to TN=467 µg/l and TP=59 µg/l, which correspond well to the observations in 2016.
Results may vary when the calculations are applied per compartment (Figure 7.11). This is due
to local differences with respect to compartment properties (Table 7.2 and Table 7.3) and
loadings. While results for the North compartment seem relatively similar to those of the whole
lake, concentrations in southern compartment S1 are clearly higher, and those in S2 and S3
are lower.
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Figure 7.10, Relation between thermocline depth and total nitrogen (TN) and total phosphorous (TP) concentrations
for the whole lake in 2015 as calculated by the budget model.
Figure 7.11, Assuming a thermocline depth of 50m, total nitrogen (TN) and total phosphorous (TP) concentrations
vary across the lake compartments in 2015 as calculated by the budget model.
The resulting concentrations do not represent the state at the moment of loading, but the
eventual equilibrium that will be reached in the lake compartment over time. Figure 7.12 shows
an example of a how a nutrient load would lead to increased concentrations over time, until a
certain equilibrium concentration is reached. With continuous loads, the equilibrium level would
shift up. The time required to reach the equilibrium is not known, but may be in the order of tens
of years. When the loads are reduced, the resulting concentration slowly goes down over time,
until a new equilibrium is reached (Figure 7.13).
Thermocline depth
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Figure 7.12, Nutrient concentration over time resulting from a load.
Figure 7.13, Shift in nutrient concentration over time resulting from a reduction in load.
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8 Response: water quality management
8.1 Approach
For each contributor of nutrients, potential investment scenarios are presented. Based on
the relative inputs of nutrients, aquaculture (68% of total phosphorous), livestock manure
(19%) and domestic wastewater (11%) have been identified as the starting points for
mitigating measures. Individual measures are discussed in more detail in the sections
below, as well as additional measures to reduce nutrient emissions into Lake Toba. These
additional measures have less impact on overall water quality in the lake, but do provide
other benefits that could be considered in an overall tourism development plan.
The existing Sumatra Spatial Model (section 5.1) quantified the impact of these scenarios
on nutrients, for the three largest sources: aquaculture, wastewater and livestock. In the
model, a future autonomous growth18 is based on predictions of population numbers and
land use for the catchment area of Lake Toba, not the full kabupaten surrounding the lake.
On top of this future autonomous growth, four scenarios have been applied, based on
mitigation measures for aquaculture, domestic wastewater and livestock manure. Various
interventions are possible to reduce the water quality loads into the system. The proposed
scenarios are explored to test their effectiveness in terms of resulting nutrient
concentration. Where other methods have been applied, they are briefly introduced at the
beginning of the section.
Mixing of water in the lake is not homogenous, which means that a load of nutrients in the
North does not immediately affect nutrient concentrations in the South. The mixing is an
unknown variable. Therefore, scenarios have been applied to different options for lake
compartments to show the effect of lack of mixing on the nutrient concentrations in the
lake. Figure 8.1 shows the selected zonation into four compartments. The labels N for
north, S1, S2 and S3 for the three separate southern compartments, are used in many
figures throughout this report.
Figure 8.1, Overview of the four compartments of Lake Toba in which the scenarios have been applied.
18 In the Sumatra Spatial Model, autonomous growth is a projection of population growth that would occur without
any intervention.
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Four different scenarios have been identified. Below is a general description, with a
summary of applied data in Table 8.1.
Scenario A
This is the baseline scenario, without any interventions, for comparison. For population
and livestock, the Sumatra Spatial Model calculates autonomous growth (section 7.3). For
aquaculture the 2015 production level is maintained 84,800 tons with a Food Conversion
Ratio (FCR) of 1.9. For wastewater an estimation of the current facilities is made, assuming
that even if people use on-site sanitation (such as septic tanks or latrines), these are not
functioning properly. For tourism the number of visitors according to the business as usual
forecast is selected.
Scenario B
This is the low scenario, mainly for comparison. For livestock, the Sumatra Spatial Model
calculates autonomous growth. For aquaculture, in the absence of any measures, the
production level is assumed to grow to a maximum level of 106,000 tons with a Food
Conversion Ratio (FCR) of 1.9. For wastewater a slow implementation of the currently
planned water and sanitation program is assumed, in which the number of people with
access to functioning on-site sanitation (such as septic tanks or latrines) increases from
0% in 2018 to 66% in 2022 and 94% in 2042, taking into account natural population growth.
In addition, limited investments in off-site sanitation supply 1% of the population with a
sewerage system in 2022 and 6% in 2042. For tourism, the number of visitors according
to the business as usual forecast is selected, without planning for additional sanitary
facilities. Because of the expected decline in water quality of Lake Toba, growth in
numbers of visitors will eventually decrease as well under this scenario.
Scenario C
This is the intermediate scenario, with interventions in aquaculture, livestock and
wastewater management. For aquaculture, the one remaining license is not renewed and
will expire naturally. There will be increasing pressure on fishfarmers without licenses. This
will likely result in assumed production levels of 64,000 tons in 2018, 50,000 tons in 2022
and 10,000 tons in 2042. For the management of livestock manure, biogas conversion is
promoted, resulting in 1% conversion of manure into biogas in 2018, 20% in 2022 and
40% in 2042. For wastewater, the currently water and sanitation program is implemented
as planned. Thus, the number of people with access to on-site sanitation (such as septic
tanks or latrines) increases from 50% in 2018 to 85% in 2022 and 94% in 2042. In addition,
limited investments in off-site sanitation supply 2% of the population with a sewerage
system in 2022 and 6% in 2042. As a result, the percentage of people practicing open
defecation decreases from 50% in 2018 to 13% in 2022 and 0% in 2042. For tourism, the
number of visitors according to the best-case scenario is selected, without planning for
additional sanitary facilities.
Scenario D
This is the high scenario, the most optimistic one, with interventions in aquaculture,
livestock and wastewater management. For aquaculture, an active reinforcement policy
ensures that the production level is reduced to 10,000 tons in 2022 and 2042. In addition,
better feeding practices in the remaining cages allow for a better food conversion ratio of
1.2. For the management of livestock manure, biogas conversion is promoted more
actively, resulting in 5% conversion of manure into biogas in 2018, 30% in 2022 and 60%
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in 2042. For wastewater, the water and sanitation program is accelerated with additional
funding. Thus, the number of people with access to on-site sanitation (such as septic tanks
or latrines) increases from 50% in 2018 to 69% in 2022 and then drops to 50% again in
2042. Off-site sanitation takes off so that in 2022 31% of the population is connected to a
central sewerage system, growing to 50% in 2042. As a result, the percentage of people
practicing open defaecation quickly decreases from 50% in 2018 to 0% in 2022 and 2042.
For tourism, the number of visitors according to the best case scenario is selected and
these numbers are included in the wastewater treatment plans.
Table 8.1, Overview of four investment scenarios to reduce nutrient loads into Lake Toba.
Driver Scenario A
Baseline
Scenario B
Low
Scenario C
Intermediate
Scenario D
High
Aquacultur
e
Extrapolation
of 2015
situation
Growth to
maximum potential
Gradual reduction of
production
Rigorous reduction of
production
2018
2022
2042
84,800 tons
FCR 1.9
106000 tons
FCR 1.9
64,000 tons, FRC 1.9
50,000 tons, FCR 1.9
10,000 tons, FCR 1.9
64,000 tons, FRC 1.2
10,000 tons, FCR 1.2
10,000 tons, FCR 1.2
Livestock Conversion of manure into biogas
2018
2022
2042
Extrapolation
of current
situation
Extrapolation of
current situation
1% conversion
20% conversion
40% conversion
5% conversion
30% conversion
60% conversion
Wastewater
No
intervention
Slow
implementation
Implementation as
planned
Accelerated
implementation
2018
2022
2042
On-site: 50%
On-site: 50%
On-site: 50%
On-site: 50%
On-site: 66%, Central : 1%
On-site: 94%, Central : 6%
On-site: 50%
On-site: 85%, Central: 2%
On-site: 94%, Central: 6%
On-site: 50%
On-site: 69%, Central: 31%
On-site: 50%, Central: 50%
Tourists per
year
Business as
usual
Business as usual Best case Best case
2018
2022
2042
1,802,200
2,059,000
2,307,000
1,802,200
2,059,000
2,307,000
1,802,200
2,212,000
3,410,300
1,802,200
2,212,000
3,410,300
The potential impact of these scenarios is shown in the graphs below, showing the relative
contribution of each driver to nitrogen (Figure 8.2) and phosphorous (Figure 8.3) loads in
Lake Toba. Clearly the intermediate C and high D scenarios have most substantial impacts
on nutrient loadings. For nitrogen, there is hardly any visible impact from interventions in
livestock and wastewater. For phosphorous this is somewhat more visible, but true
reductions are only achieved when aquaculture is reduced (blue colour in intermediate C
and high D scenarios). In the next sections the individual contributions for aquaculture,
livestock and wastewater on nutrient loads and concentrations are explained. At the end
of the chapter, the impact of combined scenarios on nutrient loads and concentrations is
presented for each of the four lake compartments.
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Figure 8.2, Nutrient loads of total nitrogen resulting from four different scenarios with combined measures in
management of nutrient emissions from aquaculture, livestock manure and wastewater, in the whole
Lake Toba (as one compartment). See Table 8.1 for the input data in each of the scenarios.
Figure 8.3, Nutrient loads of total phosphorous resulting from four different scenarios with combined
measures in management of nutrient emissions from aquaculture, livestock manure and wastewater,
in the whole Lake Toba (as one compartment). See Table 8.1 for the input data in each of the
scenarios.
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8.2 Aquaculture
8.2.1 Investment scenario
8.2.1.1 Infrastructure
The main interventions in aquaculture would be institutional in nature. However, supporting technical measures, not limited to infrastructure, could play a role. In existing aquafarms, the feeding efficiency could be increased by changing the stock/feed ratio, breeding different types of fish and using alternative feed. Such interventions are part and parcel of good aquaculture business models as efficient businesses make more profit, and the related investments are borne by the companies themselves.
For 2015 the production of PT Aquafarm Nusantara (PTAN) was modelled at the maximum
licensed amount of 36,000 tons of fish and that of PT Suri Tani Pemuka at 9,700 tons
(Table 5.2). Small-scale aquaculture farmers produced around 39,100 tons and the total
fish production at Lake Toba was set at 84,800 tons in 2015 (Table 5.2).
In 2016 the production had dropped to 74,400 tons, mainly because of the low production
at PT Suri Tani Pemuka (Table 2.3). At the same time, PTAN moved some of its cages
from the coast of Samosir in the northern compartment to the sourthern compartment S2.
Since 2016, when several districts took action to reduce aquaculture (section 3.4.4.1),
many smallholders across Lake Toba abandoned their cages. Subsequently, their total
production dropped from some 16,400 tons in 2015 (Table 5.2) to approximately half that
level in 2017 (sections 8.4.2.4 and 8.4.3). Those in Haranggoal Bay took this opportunity
and increased their production (Table 8.5).
Whereas the fish cages are located in lake compartments, their owners reside in districts.
The aquaculture producers in Haranggoal Bay are mainly from the district of Simalungun
and for them it is a major source of income. The other smallholders live across all of the
districts that surround Lake Toba. Many of them have abandoned their fish cages since
2016. Some rent out their overgrown cages, as pontoon or jetty for fishing. Tourists pay a
fee to use the cages for sport fishing on the lake. The people who still have productive fish
cages spread around Lake Toba, reside in various districts, not necessarily near their
cages. They serve tourism as well, because the fish is sold to local restaurants, where it
is served as a special dish of the region.
8.2.1.2 Institutional
An obvious scenario for reducing nutrient loads from aquaculture would be via licenses.
With the exception of PT Aquafarm Nusantara, none of the producers had formal licenses
in 2017 (Table 3.1). More information is needed on the extent of current aquaculture
activities (see section 8.2.1.3). Subsequently, concerted efforts are needed to gradually
phase out the existing licenses by not issuing new licenses and not renew the expired
ones, or only temporarily renew for a limited period, and improve compliance (scenario C).
Or a more active approach could be selected, in which no licences are issued or renewed
at all, and compliance is enforced immediately (scenario D). This would speed up the
process of reducing the nutrient load from aquaculture into Lake Toba. The purpose of this
scenario would be to achieve the carrying capacity limit of 10,000 tons per year by 2022.
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At the time of this draft report,19 the status of the PTAN license is unclear. Should this
license not expire prior to 2022, other options should be explored to achieve this scenario;
perhaps activey revoke the license of PT Aquafarm Nusantara. This may require an
intensive political process, for instance resulting in a new presidential decree, with
subsequent institutional backup.
For smallholders, who all operate without a license, a different approach, with emphasis
on law enforcement, is necessary. These people have been allowed to practise
aquaculture for several years. The producers in Haranggoal Bay, in the district of
Simalungun depend on aquaculture for their livelihoods. The investment scenarios
envisage a modest production level in Haranggoal Bay, of some 5,000 tons per year in
total. A similar quantity could be tolerated for the other smallholders, spread around Lake
Toba. Together, all smallholders could produce the maximum of 10,000 tons per year.
However, they need support to do this at the right place, i.e. at least 10 m away from the
shore, and where the water is at least 100m deep. Technical support and capacity building
efforts are also required to help these smallholders increase their efficiency so that they
can eventually achieve a food conversion ratio of 1.2.
Law enforcement on licensing and aquaculture practices (section 3.4.2) has a key role to
play in rolling out these strategies. Civil servant investigators, for instance under
responsibility of the Ministry of Marine and Fisheries, or the Ministry of Public Works and
Housing, can act on the information collected in the monitoring survey (see section 8.2.1.3)
and start court cases against companies or individuals that operate unlicensed
aquaculture farms.
For smallholders who may only have a few fish cages, as well as for people currently
working at the large aquaculture companies, alternative livelihood options need to be
supported. Several of the current individual aquaculture farmers used to practise
horticulture and grew cops such as onions. With some government support, they could
explore other profitable livelihood options, for instance in fisheries, organic farming or
(eco)tourism. Dedicated trainings could be developed by the ministries of Marine and
Fisheries, Agriculture, and Tourism, and delivered by the line agencies at the kecamatan
level, for instance the agricultural extension centers. Local foundations could also play a
role, for instance Yayasan Bina Sarana Bakti located in Ciawi, Bogor, that has been
established since 1984. The local government can collaborate with the tourism sector in
market development, boosting demand for native fish (e.g. batak or jurung) and vegetables
amongst tourists as well as for local consumption.
8.2.1.3 Information
The various strategies proposed above would benefit from sector-specific studies to further
guide the development of training and other supporting measures. A first step is to take
stock of the current licensing status and process in more detail (see section 8.2.1.3). This
effort would have to be supported with a strong legal mandate, not only to provide more
in-depth information on the process of licensing (section 3.4.4.1), but also to reveal more
details on the exact extent, validity and limitations of issued licenses. This includes
19 The Consultant will seek to close this information gap.
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guidelines or restrictions on for instance distance from the shore, minimum water depth
and maximum Secchi depth where aquaculture is permitted.
In addition, information has to be collected on the current aquaculture activities
themselves. At the time of this study (2017), all fish cages except those of PTAN are
operated without a license. A monitoring strategy is required to check where exactly the
fish cages are located, who owns them and how they are operated. This would include
monitoring of good practice, such as whether the minimum distance of the cages is indeed
10 meters from the shore in areas of at least 100 meters deep, as specified in Presidential
Regulation No. 81/2014 (section 3.4.2). Local leaders (tokoh adat) may play a role in this
as part of a participatory monitoring program.
8.2.1.4 Costed scenarios
Intermediate scenario C envisages a relatively slow phase-out of aquaculture: no new
licenses are issued and the remaining one for PT Aquafarm Nusantara is assumed to
expire between 2022 and 2042. At the same time, smallholders in Haranggoal Bay and
elsewhere at Lake Toba are not immediately forced to abandon the remaining fish cages.
Table 8.2 shows how the resulting fish production would be distributed over the
compartments. PT Aquafarm Nusantara will continue to produce 30,000 tons in 2018 and
2022 while PT Suri Tani Pemuka will phase out production from 4,000 tons in 2018 to none
in 2022. Aquaculture farmers in Harangoal Bay will reduce production from 23,100 tons in
2018 to 13,100 tons in 2022 and 5,000 tons in 2042. Other smallholders, spread around
Lake Toba and mainly producing fish for the local restaurants, will together produce 6,900
tons in 2018 and 2022, and 5,000 tons in 2042. In the small and fragile compartment S1
no aquaculture activities would be allowed in 2042. For Scenario C a Food Conversion
Ratio of 1.9 is assumed.
Table 8.2, Projected fish production in 2018, 2022 and 2042 in intermediate scenario C across the
compartments per group of aquaculture producers (in tons of fish per year).
Producer Estimated production 2018
N S1 S2 S3 total
PT Aquafarm
Nusantara
9,000 21,000 30,000
PT Suri Tani
Pemuka
4,000 4,000
Haranggoal Bay 23,100 23,100
Other smallholders 3,000 1,000 2,000 900 6,900
Total 39,100 1,000 23,000 900 64,000
Percentage
production
61% 2% 36% 1%
Percentage emission 69% 1% 29% 1%
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Estimated production 2022
Producer N S1 S2 S3 total
PT Aquafarm
Nusantara
9,000 21,000 30,000
PT Suri Tani
Pemuka
0 0
Haranggoal Bay 13,100 13,100
Other smallholders 3,000 1,000 2,000 900 6,900
Total 25,100 1,000 23,000 900 50,000
Percentage
production
50% 2% 46% 2%
Percentage emission 58% 2% 39% 2%
Estimated production 2042
Producer N S1 S2 S3 total
PT Aquafarm
Nusantara
0 0
PT Suri Tani
Pemuka
0 0
Haranggoal Bay 5,000 5,000
Other smallholders 2,100 0 2,000 900 5,000
Total 7,100 0 2,000 900 10,000
Percentage
production
71% 0% 20% 9%
Percentage emission 80% 0% 14% 6%
Contrary, scenario D aims at a rapid decrease in fish production with immediate action
against unlicensed aquafarming and no new or renewed licenses. The one remaining
license for PT Aquafarm Nusantara is assumed to either expire before 2022 or to be
revoked before that year. Compliance with the law will be actively enforced and most
smallholders will be forced to abandon the remaining fish cages. The aquaculture farmers
at Harangoal Bay as well as the other smallholders will be allowed to continue aquaculture
at a lower level, each group producing no more than 5,000 tons per year. In the small and
fragile compartment S1 no aquaculture activities would be allowed in 2022. With better
feeding practices, they would be able to reach this production with less feed. Thus, the
targeted fish production of 10,000 tons for the whole of Lake Toba will be reached by 2022,
efficiently produced with a food conversion ratio of 1.2.
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Table 8.3, Projected fish production in 2018, 2022 and 2042 in high scenario D across the compartments per
group of aquaculture producers (in tons of fish per year).
Producer Estimated production 2018
N S1 S2 S3 Total
PT Aquafarm
Nusantara
9,000 21,000 30,000
PT Suri Tani
Pemuka
4,000 4,000
Haranggoal Bay 23,100 23,100
Other smallholders 3,000 1,000 2,000 900 6,900
Total 39,100 1,000 23,000 900 64,000
Percentage
production
61% 2% 36% 1%
Percentage emission 69% 1% 29% 1%
Producer Estimated production 2022 and 2042
N S1 S2 S3 total
PT Aquafarm
Nusantara
0 0
PT Suri Tani
Pemuka
0 0
Haranggoal Bay 5,000 5,000
Other smallholders 2,100 0 2,000 900 5,000
Total 7,100 0 2,000 900 10,000
Percentage
production
71% 0% 20% 9%
Percentage emission 80% 0% 14% 6%
In Table 8.4 the various potential interventions are listed with estimated costs under two
scenarios, intermediate scenario C and high scenario D.
Table 8.4, Overview of estimated investment costs for the period 2018-2022 to reduce nutrient loads from
aquaculture into Lake Toba, in an intermediate scenario C (target production of 50,000 tons in 2022;
FCR 1.9) and a high scenario D (target production of 10,000 tons in 2022; FRC 1.2).
Summary
investments
C. Intermediate D. High
Duration
(years) OPEX20 OPEX Responsibility
Infrastructure
Buy better feed 0 50 Aquaculture companies,
smallholders
5
Institutional
Coordination 200 400 Ministry of Marine and
Fisheries, local government
5
Law enforcement:
monitoring
100 200 ATR BPN, Ministry of
Marine and Fisheries, BWS
Sumatera II, traditional
leaders
5
20 OPEX = Operational Expenses, running costs; total fore five years.
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Summary
investments
C. Intermediate D. High
Duration
(years) OPEX20 OPEX Responsibility
Law enforcement:
investigation
50 100 Civil servant investigators
under ATR BPN, Ministry of
Marine and Fisheries, and
Ministry of Public Works
and Housing
5
Training on fisheries 600 4,000 Ministry of Marine and
Fisheries
3
Training on organic
farming
1,200 4,000 Ministry of Agriculture, local
foundations
3
Training on
ecotourism
600 4,000 Ministry of Tourism 3
Market development 500 4,000 local government, tourism
sector
5
Information
Guiding studies 1,500 4,500 Ministry of Marine and
Fisheries
1,5
Awareness campaign 4,950 12,900 Ministry of Environment
and Forestry, Ministry of
Marine and Fisheries
3
Total (million IDR) 9,700 34,150
US$ equivalent 718,785 2,530,567
8.2.2 Impact on nutrients
The effects of measures to reduce pollution in aquaculture are the largest compared to
measures taken on other sources of pollution. The impact of reduced fish production has
been modelled for the two investment scenarios in comparison with a baseline and
business-as-usual scenario: A. Baseline: Fish production as is, at 84,800 tons per year with FRC 1.9;
B. Low: Let capacity grow to maximum of licenses: 106,000 tons with FRC 1.9;
C. Intermediate: No new licenses, let licenses expire naturally and enforce gradually
from 64,000 tons in 2018 to 50,000 tons in 2022 and 10,000 tons in 2042, all with
FRC 1.9;
D. High: Actively reduce aquaculture from 64,000 tons in 2018 to 10,000 tons from 2022
onwards, with FRC 1.2.
Similar to the load calculations in section 5.1.2, emissions per fish cage are the same for
commercial and smallholder aquaculture producers. Commercial producers have a double
yield per cage as they can produce more efficiently. This explains why the percentages of
fish production in each compartment are not the same as the percentages emissions.
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In the baseline scenario A the same total fish production of 2015 is taken (Table 5.2) and
kept at a constant level from 2018 to 2042. However, the distribution across the
compartments has shifted since 2015 (section 8.2.1.1). In 2016, PTAN has moved some
of its cages from the north to the southern compartment S2. Since 2016, when several
districts took action to reduce aquaculture (section 3.4.4.1), many smallholders across
Lake Toba abandoned their cages and production dropped from 16,400 tons in 2015 to
8,200 tons in 2018. Those in Haranggoal Bay took this opportunity and increased their
production from 22,700 tons in 2015 to 30,900 tons in 2018 (Table 8.5).
Table 8.5, Projected fish production in 2018, 2022 and 2042 in baseline scenario A across the compartments
per group of aquacultureproducers (in tons of fish per year).
Producer Estimated production
N S1 S2 S3 total
PT Aquafarm
Nusantara 10,800 25,200 36,000
PT Suri Tani
Pemuka 9,700 9,700
Haranggoal Bay 30,900 30,900
Other smallholders 3,300 1,600 2,400 900 8,200
Total 54,700 1,600 27,600 900 84,800
Percentage21
production 65% 2% 33% 1%
Percentage emission 72% 3% 24% 1%
Contrarily, low investment scenario B allows for unlimited growth up to a total production
level of 106,000 tons per year from 2018 to 2042. PT Aquafarm Nusantara would produce
36,000 tons per year according to its. PT Suri Tani Pemuka is assumed to increase
production to the level of the original license, i.e. 30,000 tons per year. Aquaculture at
Haranggoal Bay will increase to 31,800 tons per year, while the total production of other
smallholders will stay at 8,200 tons per year (Table 8.6).
Table 8.6, Projected fish production in 2018, 2022 and 2042 in low investment scenario B across the
compartments per group of aquacultureproducers (in tons of fish per year).
Producer Estimated production
N S1 S2 S3 total
PT Aquafarm
Nusantara 10,800 25,200 36,000
PT Suri Tani
Pemuka 30,000 30,000
Haranggoal Bay 31,800 31,800
Other smallholders 3,300 1,600 2,400 900 8,200
Total 75,900 1,600 27,600 900 106,000
Percentage
production 72% 2% 26% 1%
Percentage emission 79% 1% 20% 1%
21 Because of rounding, percentages in tables may not exactly add up to 100%. The model applies the calculated,
non-rounded percentages.
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Nitrogen (N) and phosphorous (P) loads would drop dramatically when fish production is
limited to 10,000 tons/year. See Figure 8.4 for the whole lake compartment estimates. The
graphs show the high load under the static baseline scenario A with current production of
84,800 tons, and even higher loads under the low scenario B with the maximum fish
production of 106,000 tons. The intermediate scenario C, with gradually decreasing
production over time, gives lower loads. Obviously, the high scenario D has lowest loads.
In 2024 the difference between scenario C and D is clearly visible. Due to the Food
Conversion Ratio (FCR) of 1.2 in scenario D, its loads are almost half of those in scenario
C, where a food conversion ratio of 1.9 has been applied. The resulting load in 2042 for
scenario C is what would have been achieved in 2022 for scenario D if a food conversion
ratio of 1.9 instead of 1.2 had been applied.
Figure 8.4, Projected impacts of two intervention scenarios (C & D) and two comparison scenarios (A & B) on
loads from aquaculture and resulting long-term concentrations of nitrogen (left) and phosphorous
(right) for the whole of Lake Toba.
In Figure 8.4 projected nutrient concentrations are indicated, that would be the long-term
result from the load in a certain year, if aquaculture would be the only source of nitrogen
and phosphorous. The displayed concentrations thus represent equilibrium
concentrations on the basis of input data for 2018, 2022 and 2042. It may take tens of
years to achieve each of these equilibrium states (Figure 7.13) and in reality additional
sources will add to the load (section 0). Limits for oligotrophic and mesotrophic state have
been indicated for phosphorous at 10 and 30 μg/l respectively, and for nitrogen the
oligotrophic limit of 350 μg/l is displayed (based on Nürnberg, 1996; Table C.2 in Annex
C.3). Figure 8.5 shows the nitrogen and phosphorous loads and lon-term concentration
under the four aquaculture scenarios applied to the best zonation in four compartments.
The graphs show loads and concentrations by compartment at fixed scales to enable
comparisons between compartments.
The reductions in nutrient loads are particularly strong in the northern compartment N,
where many fish cages are situated, and in S2. In all compartments the long-term
phosphorous concentrations would drop below the limit of 10 μg/l, at minimum fish
production levels (scenario C in 2042 and scenario D in 2022 and 2042). This means that
the maximum production level of 10,000 tons/year on its own would not threaten the long-
term oligotrophic state for the compartments. However, continued loads may still lead to
local eutrophication effects.
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Figure 8.5, Projected impacts of two intervention scenarios (C & D) and two comparison scenarios (A & B) on
loads from aquaculture and resulting long-term concentrations of nitrogen (left) and phosphorous
(right) across the four compartments North, S1, S2, and S3 of Lake Toba.
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8.3 Managing livestock manure
8.3.1 Investment scenarios
Converting livestock dung into a valuable energy source (e.g. biogas) is one way to avoid
pollution from manure entering Lake Toba. Unless animal manure is managed carefully to
minimize odor, nutrient losses and emissions, it becomes a source of pollution and a threat
to aquifers and surface waters. It can also be a direct threat to human and livestock health.
Used appropriately, livestock manure is a valuable resource that can replace significant
amounts of chemical fertilizers. As biogas, it becomes a renewable energy source capable
of reducing the use of fuel-wood and fossil fuels.
The Indonesian Domestic Biogas Programme (IDBP) is in Indonesia better known as the
BIRU programme; an acronym of Biogas Rumah, or ‘biogas for the home’. BIRU aims to
promote the use of bio-digesters as a local, sustainable, energy source by developing the
market while working towards the development of a commercial, market-oriented sector,
leading to the creation of jobs. It is an initiative of two Dutch NGOs, Hivos and SNV. Closely
working with the Indonesian Ministry of Energy and Mineral Resources, the program is
implemented by Yayasan Rumah Energi (YRE) with funds made available by EnDev
(Energising Development), the Norwegian and Netherlands Embassies, together with
partners in promoting access to a modern and sustainable form of renewable energy for
rural people. BIRU started in May 2009 with financial support from the Netherlands
Embassy. As of November 2015, it has built 16,015 biogas digesters in nine provinces in
Indonesia. At the moment, BIRU works in ten provinces in Indonesia: Lampung, West
Java, Banten, Central Java, DI Yogyakarta, East Java, South Sulawesi, Bali, West Nusa
Tenggara dan East Nusa Tenggara (Sumba).
Additional recommendations on the conversion of livestock manure into biogas and more
generally, on the sustainable management of manure, can be found in Annex L.
8.3.1.1 Biogas infrastructure
The amount of biogas production differs per animal (Table 8.7). For comparison, 1 m3 of
biogas equals ± 0.46 kg LPG, ± 0.62 litre of kerosene, or ± 3.5 kg of wood.
Table 8.7, Biogas production from selected domestic animals
Organic material Biogas produced (l/kg)
Cow dung 40
Buffalo dung 30
Pig dung 60
Chicken dung 70
The fixed dome biogas plant has a minimum life of 15 years if properly operated and
maintained. Maintenance is easy; it merely requires the occasional checking and – if
necessary – repair of pipes and fittings. To operate one unit, the farmer needs to have at
least two cows or seven pigs (or a flock of 170 poultry) to produce enough feed for the
reactor to be able to generate sufficient gas to meet their daily basic cooking and lighting
needs22.
22 www.biru.or.id
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At household level the choice between an individual biogas and communal biogas
installation for several households depends on the distance between houses. The cost to
construct a biogas plant at household level is in the range IDR 6.0 – 7.5 million. A
successful pilot (suggested at minimum three areas), with support of intensive advocacy
and training, will increase the trust of the community to accept and replicate the initiative
in other places.
Under the intermediate scenario, 11 pilot biogas plants will be constructed and double this
number, 22 biogas plants, under the high investment scenario. Likewise, the second phase
of upscaling will be implemented with double efforts under the high scenario to ensure
30% update by 2022, as compared to the intermediate one (aimed at 20% uptake by
2022).
8.3.1.2 Institutional
An action plan for the management of pollution from livestock covering all municipalities
around Lake Toba should be considered. It has to be facilitated by the Livestock and
Animal Health Agency of North Sumatra Province in coordination with related agencies in
each kabupaten and the Lake Toba Tourism Area Management Authority. Cooperation
with Yayasan Rumah Energi (YRE) or others for the implementation of biogas production
should be further investigated.
Supporting institutional efforts such as coordination between kabupaten and training
efforts under the high investment scenario are roughly one and a half to two times that of
the intermediate scenario.
8.3.1.3 Information
There is insufficient reliable information on the concentration of livestock owned by
individual farmers and by big companies. Guiding studies help to select the most promising
sites for the pilot biogas plants and for trainings.
8.3.1.4 Costed scenarios
In Table 8.8 the various potential interventions introduced above are listed with estimated costs under two scenarios, grouped into categories for infrastructure, institutional activities and information campaigns. More detail on the proposed activities is provided in annex L. Under the intermediate scenario C, 17 pilot biogas plants will be constructed, supported with upscaling activities and training resulting in 20% uptake in 2022. A higher number of 22 biogas plants will be implemented under the high investment scenario D, coupled with more intensive supporting activities, resulting in 30% uptake by 2022.
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Table 8.8, Overview of estimated investment costs for the period 2018-2022 to reduce nutrient loads from
livestock manure into Lake Toba, in an intermediate scenario C (conversion of 20% of manure into
biogas in 2022) and a high scenario D (conversion of 30% of manure into biogas in 2022).
C. Intermediate D. High
CAPEX23 OPEX24 CAPEX OPEX Responsibility Duration
Infrastructure
Pilot project biogas
340 26 440 33 Dinas Peternakan at 7 kabupaten - coordinated by Dinas Peternakan & Kesehatan Hewan (DPKH) provinsi
18 months
Upscaling biogas installations
5,000 1,000 7,000 1,400 4 years
Institutional
Coordination
300
400
DPKH Province Sumatera Utara
5 years
Training
2,500
4,000 5 years
Information
Guiding studies
3,000
4,500 DPKH Kabupaten & Province Sumatera Utara
18 months
Campaign 750 1,000
Subtotal 5,340 7,576 7,440 11,333
Total (million IDR)
12,916 18,773
US$ equivalent (000, split)
396 561 551 840
US$ equivalent (000, total)
957 1,391
8.3.2 Impacts on nutrients
Future autonomous growth is based on predictions of population numbers and land use of
the Sumatra Spatial Model (baseline). On top of this future autonomous growth, the two
investment scenarios were applied and compared to the baseline. These are as follows:
A. Minimum: Business as usual, including the projected growth, no mitigations;
B. Low: Same as A;
23 CAPEX = Capital Expenses. 24 OPEX = Operational Expenses, running costs; total fore five years.
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C. Intermediate: Increasing conversion of manure into biogas, resulting in 1% uptake in
2018, 20% in 2022 and 40% in 2042, with an assumed efficiency of 70% reduction of
both nitrogen and phosphorous loads;
D. High: Accellerated conversion of manure into biogas, resulting in 5% uptake in 2018,
30% in 2022 and 60% in 2042, with an assumed efficiency of 70% reduction of both
nitrogen and phosphorous loads.
The effects of livestock nutrient emission measures are shown in Figure 8.6 for the whole
lake compartment estimates. The impact of the measures is limited. The intermediate
scenario C can just compensate for autonomous growth. For phosphorous the impact is a
bit more pronounced, particularly for high scenario D.
Figure 8.6, Projected impacts of two intervention scenarios (C & D) and a comparison scenario (A & B) on
loads from livestock and resulting long-term concentrations25 of nitrogen (left) and phosphorous (right)
for the whole of Lake Toba.
In Figure 8.6 projected nutrient concentrations are indicated, that would be the long-term
result from the load in a certain year, if livestock manure would be the only source of
nitrogen and phosphorous. The displayed concentrations thus represent equilibrium
concentrations on the basis of input data for 2018, 2022 and 2042. It may take tens of
years to achieve each of these equilibrium states (Figure 7.13) and in reality additional
sources will add to the load (section 0). Limits for oligotrophic and mesotrophic state have
been indicated for phosphorous at 10 and 30 μg/l respectively (based on Nürnberg, 1996;
Table C.2 in Annex C.3). For nitrogen, the resulting concentrations stayed well below the
limit of 350 μg/l for an oligotrophic state.
Figure 8.7 shows the nitrogen and phosphorous loads and long-term concentration under
the three livestock scenarios (scenarios A and B are the same) applied to the best zonation
in three compartments. For compartment S3 insufficient data were available so no reliable
modelling could be performed. For calculations of the loads in the whole lake, this made
no significant difference. The graphs show loads and concentrations by compartment at
fixed scales to enable comparisons between compartments.
The graphs show increasing loads under the autonomous growth scenario A/B. The
conversion of biogas at intermediate intensity in scenario C and even at higher intensity in
scenario D has a limited effect on nutrient loads. However, in the northern compartment
25 As scenario A and B are the same, the concentrations for scenario A are not visible; these are the same as for
scenario B.
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N, the reduction of phosphorous loads under the high scenario D would eventually lead to
concentrations below the oligotrophic limit of 10 μg/l. In the smallest southern compartment
S1 the low loads would lead to concentrations at the mesotrophic level, even when manure
is converted into biogas (scenarios C and D). Without interventions, scenario A/B, the
increasing loads would contribute to a eutrophic state.
Figure 8.7, Projected impacts of two intervention scenarios (C & D) and a comparison scenario (A & B) on
loads from livestock and resulting long-term concentrations26 of nitrogen (left) and phosphorous (right)
across three compartments North, S1, and S2 of Lake Toba. For compartment S3 insufficient data
were available.
26 As scenario A and B are the same, the concentrations for scenario A are not visible; these are the same as for
scenario B.
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8.4 Wastewater (domestic and tourism) management
8.4.1 Approach and background
This section covers domestic wastewater (sewage), with special attention to the tourism
industry. The initial input for the inventory of the existing and planned infrastructure related
to sewage is based on the sanitation strategies (e.g. BPS, SSK, MPS) for each kabupaten
in the catchment (Annex M, see also USDP, 2015). The selection of type of wastewater
treatment facilities is based on the approach explained in the Buku Referensi (TTPS,
2009). This approach aims to reduce the risk to health and environment at the lowest costs.
Thus, in urban areas with high population densities and high exposure levels, on-site
systems (septic tanks) are no longer preferred and off-site systems with improved
performance (removal efficiencies) are selected, which is a general applied approach
(UNEP, 2004).
Increasing the water supply coverage increases wastewater flow, but this has no impact
on the wastewater investments as these depend on the number of people covered and
unit investment cost per person. In the calculations below an assumption of average
wastewater flows based on full water supply coverage has been included.
An important input in terms of present tourism activity (numbers of visitors and tourist
centers) and its expected development is the recently carried out tourism demand
assessment (section 7.3.3).
Most hotels and restaurants still discharge the wastewater directly into Lake Toba. Out of
45 hotels only three are connected to the sewer system. The system is under the
responsibility of PDAM Tirtanadi. The facilities have not been regularly maintained and are
currently in a poor condition. The one wastewater treatment plant (IPAL) in the Lake Toba
area, is in Parapat. It has been constructed in 1996 with a loan from the Japanese
Overseas Economic Cooperation Fund, OECF (IDR 7.3 billion) and is operational since
2000. The system has 15,000m sewerage pipeline equipped with 128 man-holes and three
pump rooms. It has a capacity to treat 900 to 2,000 m3/day (equal to 3,000 house
connections) and occupies two hectares of land. In 2017 only 200 households are
connected, so the IPAL functions at only 10% of capacity (personal information, Mr Joni
Mulyadi, manager at PDAM Tirtabadi, November 2017). The pumps and other equipment
require rehabilitation. In addition, the sewer pipes are leaking.
New wastewater treatment facilities have been planned for Balige and Toba Samosir
Districts. However, a budget has not been secured yet and no timeline for implementation
has been set. The implementation of new wastewater treatment plants (IPAL - Instalasi
Pengolahan Air Limbah) or fecal sludge treatment plants (IPLT - Instalasi Pengolah
Lumpur Tinja) are often constrained due to delays from the land acquisition process. Many
land plots have cultural significance and require confirmation and approval from the family
or the clan that owns the land before any infrastructure can be built).
Domestic wastewater may not be the major contributor to the pollution of Lake Toba. Other
aspects such as health, wellbeing and environmental amenities make it necessary to
address proper disposal of wastewater—in particular in the light of tourism development.
For the assessment of required infrastructure, calculations have been made for all desa
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and keluhuran within the catchment area draining into the lake, hence not for the entire
kabupaten. For tourists, peak numbers of visitors have been calculated as follows (based
on Table 7.1): 300,368 in 2018 for all scenarios, 343,114 in 2022 and 384,500 in 2042 for
scenarios A and B, and 368,623 in 2022 and 568,363 for scenarios C and D.
8.4.2 Investment scenarios
8.4.2.1 Infrastructure
As a no-regret measure that can be implemented with relative ease, the existing sewerage
system of PDAM Tirtanadi in Parapat (one of the tourism areas) should be rehabilitated.
The wastewater treatment plant (WWTP) uses a conventional system consisting of
aeration ponds, facultative ponds and maturation ponds, all equipped with aerators. Since
land availability is an issue, one feasible option would be to upgrade the treatment process
at the WWTP, making it more efficient with a lower foot-print.
For the medium (until 2022) and longer term (until 2042) three scenarios are considered.
The intermediate one is the implementation of the national policy (USDP, 2015)27. The
high scenario targets an accelerated implementation of this plan, aiming for 100%
coverage in 2022 instead of 2042. It envisages additional facilities for the core tourist areas
at the southern and eastern shores of Lake Toba (section 7.3.3). These areas have higher
population densities and the sanitation services switch from community-based to off-site
wastewater treatment. The low scenario assumes a slower speed of implementation,
taking into account the lengthy processes to release sufficient funds. Table 8.1 provides
an overview of the percentages of access to various facilities over time in the different
scenarios.
In terms of tourism, the baseline and low scenario apply the number of visitors in the
‘business as usual’ projection (Table 7.1). The intermediate scenario is based on the ‘best
case’ number of visitors, but does not foresee additional infrastructure. The high scenario
uses the ‘best case’ projection with additional treatment facilities.
In the low and intermediate scenario, the national targets and type selection (Table 8.9)
applied to the Lake Toba catchment results in a focus on community based systems
(Sanimas) as well as individual septic tanks for rural areas (City Wide Sanitation
Investment Program, 2016). In urban areas off-site systems (Kawasan/Pusat) are applied;
only 5%-10% of the population will be on such systems by 2042. The majority of domestic
wastewater will not have advanced treatment (no nutrient removal). Under the low
scenario, a large part of direct cost is allocated to the users/community (30%), resulting in
a slower speed of implementation.
27 The original budget in the ADB study turned out to under-estimate the costs of off-site sanitation; in the
investment scenarios presented here, this bas been corrected.
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Table 8.9, Selection criteria for type of sanitation services (see also Table M.1).
Population density
(pp/ha) <25 25-100 100-175 175-250 >250
Urban function
(BPS, RTRW) no yes no yes no yes no yes no yes
On-site
1
Community based
2
Off-site (centralized)
Kawasan
1
2
Terpusat
3
Notes:
1 Existing areas, consider on-site systems; for new areas IPAL kawasan to be considered;
2 For very high dense rural areas both IPAL communal and kawasan could be considered;
3 There is no clear separation between IPAL kawasan and terpusat; off-site typically involves systems of >
10,000 HH;
4 Rural population <25 pp/ha not served by IPLT until 2022.
In the high scenario the application of higher targets and off-site systems for tourist areas
on Lake Toba catchment results in a shift from community based systems (Sanimas) to
off-site (IPAL Kawasan). There is only a small reduction in individual septic tanks. Half of
the population will be on off-site systems by 2042; half of domestic wastewater will have
advanced treatment (incl. nutrient removal). Compared to the other scenarios, the
accelerated approach and choice for more centralized systems results in a major increase
in the total cost. This is coupled with a major decrease in direct cost to users in the
community (~0.4x) compared to the base scenario. More details on the funding
mechanisms for wastewater interventions can be found in Annex M.
8.4.2.2 Institutional
While the recommendations for wastewater management are based on national policies
for sanitation, the implementation requires institutional support as well (USDP, 2015). For
the Lake Toba area, it needs to be clear who is responsible for catchment-wide sanitation
services. Figure 8.8 shows the steps and activities to arrive sustainable sanitation services
in priority areas. For more details on the institutional aspects, see Annex M.4 that is largely
based on the City-Wide Sanitation Investment Program (2016).
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Figure 8.8, Sanitation implementation schedule (based on City Wide Sanitation Investment Program,
2016).
Local government has an important role to play in the planning, funding and operation of
improved wastewater management facilities. An incentive program could support the local
government to align a faecal sludge management program with improving on-site
sanitation. This would need to be supported by local and national funding for priority
measures that directly increase levels of access to improved waste water management
(no-regret measures). Subsidies will be needed to cover the gap between what households
can pay and the actual costs, particularly for low income and disadvantaged households.
Sewerage systems with wastewater treatment plants are under the responsibility of PDAM
Tirtanadi i.e. the wastewater section. Figure 8.9 shows the institional arrangements
required for wastewater interventions at Parapat. This encompasses the entire supply
chain to enhance sustainability beyond the construction phase. Similar diagrams display
the potential arrangements for other wastewater management options in Annex M.2.
Communal systems, typically shallow sewers with primary treatment plants, are managed
by the community. For the on-site system, the septic tank is owned by each household
while the sludge treatment plant (IPLT) is under the responsibility of the local government.
Costs of sludge collection are included in the operational costs of the on-site and
community-based systems.
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Figure 8.9, Supply chain for best wastewater investment scenarios at Parapat (after Tilley et al. 2008).
8.4.2.3 Information
In most areas wastewater is under the responsibility of the local Public Works Agency
(Dinas PU). However, if sustainability of the system has to be ensured, other agencies
need to be involved, such as the Health Agency (Dinas Kesehatan) for advocacy and
campaigns, Communication and Information Agency (Dinas Kominfo) for advocacy and
campaigns, local Government Planning Board (Bappeda) for preparing the program and
budget allocation, and PDAM or another agency for the operation of the system. Realizing
that coordination between agencies is important, under the National Accelerated
Sanitation Development for Human Settlements Program (PPSP) a pre-requisite condition
for the municipalities to be involved in the program is that they have to establish a City
Sanitation Working Group. To make the working group effective, the Ministry of Home
Affairs has released guidance that the working group shall be chaired by the Municipal
Secretary. The kabupaten have been involved in the PPSP program. Therefore to make
the program effective the City Sanitation Working Group should be re-activated to prepare
an action program to support Lake Toba water quality improvement.
8.4.2.4 Costed scenarios
An analysis was carried out to determine the investment (CAPEX) and operational costs
(OPEX) for wastewater collection and treatment facilities. A distinction is made between
investment figures for existing and new developing areas. In this assessment, the costs
for sewer systems for new areas are expected to be reduced by 50%28 compared to the
investments in an existing area. The cost for the wastewater treatment plant (WWTP) itself
is expected to be the same either way. In Annex M.2 the complete needs assessments
according to low, intermediate and high investment scenarios are elaborated. The costs
presented in Table 8.10 are total costs based on unit cost per person over five years.
However, these cost need to be covered from different sources. These budgets need to
come from both private and public sources (City Wide Sanitation Investment Program,
2016). And the public sources can be subdivided into national and local levels as well as
by department (i.e Public Works and Ministry of Health. More on this can be found in Annex
28 Based on data of the Dutch situation it is found that more than half of the costs of the sewer system in existing
areas are related to the opening and closing of existing roads and pavements. In new developments, the
opening up of the streets is not needed and the construction of pavement is considered part of the general
development, so a 50% factor for sewer system development is applied.
User
InterfaceStorage / Primary Treatment
Transportation /
Conveyance
Centralized
TreatmentRecycle / Disposal
Recycled
sludge
Effluent to
river / lake
WC / Toilet Sewer line WWTP
Items
Infrastructure
Finance CustomerProvince /
Central GovCentral Gov.
Regulation Obligation to connect & fee
PDAM TirtanadiInstitutionEnv agency to
monitor
Customer for house connection
LG for branch sewer
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M. The cost includes capital expenses for hardware (i.e. physical measures) and
operational expenses for software (ranging from e.g. advocacy and socialization to the
collection of sludge from septic tanks).
Table 8.10, Overview of estimated investment costs for the period 2018-2022 to reduce nutrient loads from
domestic wastewater (including tourism) into Lake Toba, in a low scenario B, an intermediate and a
high scenario D. Table 8.11 shows the percentages access to each type of facility and the tourism
numbers for each scenario.
B. Low C. Intermediate D. High
CAPEX29 OPEX30 CAPEX OPEX CAPEX OPEX responsibility
Infrastructure
On-site systems 86,000 66,215 203,000 75,434 219,000 76,652 users/community,
National & Local
government Community-
based systems
474,000 22,965 848,000 41,097 349,000 16,914
IPLT 76,000 ^ 103,000
102,000 ^ National & Local
government
Medium
centralized
95,000 10,925 236,000 18,655 3,693,000 240,932 National & Local
government
Institutional and information are included in OPEX
Subtotal 731,000 100,105 1,390,00
0
135,185 4,363,000 334,498
Reserved 730,472 100,105 730,472 100,105 730,472 100,105
Extra
investment
required (106
IDR)
528 0 659,528 35,081 3,632,528 234,393
Total (million
IDR)
529 694,610 3,866,922
US$ equivalent
(000, split)
39 0 48,872 2,600 269,176 17,369
US$ equivalent
(000, total)
39 51,472 286,545
8.4.3 Impact on nutrients
For calculation of the emissions, it should be considered that many of the urban on-site
systems do not comply with the definition of a septic tank and are more like pit latrines.
The result is that there is still a lot of leakage of polluted water to the groundwater. Hence,
the effective reduction of on-site sanitation facilities (septic tanks as well as community-
based systems) is only 5%. Off-site centralized systems are more effective and are
assumed to remove 67% of nutrients (based on Kerstens et al. 2015). The resulting
percentages nutrient reduction for the three scenarios are presented in Table 8.11.
29 CAPEX = Capital Expenses. 30 OPEX = Operational Expenses, running costs; total fore five years.
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Table 8.11, Access to sanitation facilities, assumed numbers of tourists, and effective reduction of nutrient
loads from domestic wastewater according to four scenarios. See section 8.1 for more details. Scenario A
Baseline
Scenario B
Low
Scenario C
Intermediate
Scenario D
High
2018
On-site
Centralized
Peak number of
tourists
Total reduction
0%
0%
300,368
0%
0%
0%
300,368
0%
0%
0%
300,368
0%
0%
0%
300,368
0%
2022
On-site
Centralized
Peak number of
tourists
Total reduction
0%
0%
343,114
0%
66%
1%
343,114
4%
85%
2%
368,623
6%
69%
31%
368,623
24%
2042
On-site
Centralized
Peak number of
tourists
Total reduction
0%
0%
384,500
0%
94%
6%
384,500
9%
94%
6%
368,623
9%
50%
50%
368,623
36%
The effects of measures to reduce sewage flows from domestic areas and tourism are
relatively small, see Figure 8.10. The majority of the population live in non-urban areas
and will continue to be connected to septic tanks. Even under high scenario D this will still
be 50%. These on-site systems have limited effect on phosphorous and nitrogen
emissions. However, locally these effects could be higher. Under the high scenario D a
higher percentage of the population will be connected to centralized sewer-based systems.
These are more effective in reducing nutrient emissions and thus more than compensate
for population growth. As a result, nutrient loads under this scenario reach levels below
those of 2018.
Figure 8.10, Projected impacts of three intervention scenarios and a comparison scenario (A) on loads from
domestic wastewater and resulting long-term concentrations of nitrogen (left) and phosphorous (right)
for the whole of Lake Toba.
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In Figure 8.10 projected nutrient concentrations are indicated, that would be the long-term
result from the load in a certain year, if wastewater from domestic areas and tourism would
be the only source of nitrogen and phosphorous. The displayed concentrations thus
represent equilibrium concentrations on the basis of input data for 2018, 2022 and 2042.
It may take tens of years to achieve each of these equilibrium states (Figure 7.13) and in
reality additional sources will add to the load (section 0).
Figure 8.11 shows the nitrogen and phosphorous loads and long-term concentration under
four scenarios applied to the best zonation in four compartments. The graphs show loads
and concentrations by compartment at fixed scales to enable comparisons between
compartments. The phosphorous limit for oligotrophic state has been indicated at 10 μg/l
(based on Nürnberg, 1996; Table C.2 in Annex C.3). For nitrogen, the resulting
concentrations stay well below the limit of 350 μg/l for an oligotrophic state in all
compartments in all scenarios.
The graphs show increasing loads from population growth in all scenarios except the high
investment scenario D. Based on loads from domestic wastewater alone, long-term
phosphorous concentrations do not go beyond the oligotrophic limit of 10 μg/l, in the large
compartments North and S2. In the small compartment S1 even under the high investment
scenario D, concentrations would reach mesotrophic levels. In compartment S3 the high
investment scenario would manage to keep the long-term concentratioms below 10 μg/l.
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Figure 8.11, Projected impacts of three intervention scenarios and a comparison scenario on loads from
domestic wastewater and resulting long-term concentrations of nitrogen (left) and phosphorous (right)
across four compartments North, S1, S2, and S3 of Lake Toba.
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8.5 Other interventions
In the sections below, additional interventions are presented that would reduce the nutrient
load in Lake Toba. However, as these were not main drivers of water quality (together
contributing less than 2% of total phosphorous loads), their impact on improving water
quality in Lake Toba is negligible. However, their impacts on, for instance, rural
development or tourism justify inclusion in this report. Roads, hydropower and telecom are
excluded from the report. Improvements in domestic water supply may increase
wastewater flows, but this has no impact on wastewater investments as these depend on
population numbers.
Moreover, as investors are waiting to develop infrastructure around Lake Toba (section
2.1.4), these new investments all need guidance to ensure that water quality is not further
threatened. BWS Sumatera II has positively advised DLH-SU to start collaboration and
build commitment on protection of water quality with the eight district governments around
Lake Toba. In this way, all related agencies, including the police, NGOs and the media,
could be mobilized.
8.5.1 Pollution in agriculture
Pollution from rice fields and other crops may come from synthetic pesticide and fertilizer.
One way of reducing this pollution is through organic farming. As with livestock
management, organic farming could be promoted via pilot projects. New farming practices
require capacity building at local level (training). In parallel, supply chains and marketing
of the products must be secured. Recommendations on upscaling of organic horticulture
via training and market development have been included among the livelihood options
presented as alternatives to aquaculture (section 8.2.1).
Several foundations can support the pilot including providing training for interested
farmers. The existence of old small local organizations such as Water User Associations
(WUA) are eager to support better agricultural farming practices and irrigation (especially
better use of fertilizer and pesticide or transition to organic farming).
8.5.2 Solid waste management
8.5.2.1 Approach and background
At the moment, solid waste might not contribute much to the water quality degradation of
Lake Toba and therefore the impacts have not been modelled. However, this may be
different in the future with more people. Moreover, as with wastewater, aspects such as
health, well-being and environmental amenities make it necessary to address proper
disposal of solid waste—in particular in the light of tourism development.
As with (domestic) wastewater, the National Accelerated Sanitation Development for
Human Settlements Program (PPSP-2 USDP; USDP, 2015) prepared an assessment of
the country-wide solid waste funding and facilities required in the period of 2015-2019 (and
beyond) for the National Medium-Term Development Plan 2015-2019 (RPJMN 2015-
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2019). The database that was developed for this assessment was adapted (scaled down)
to the Lake Toba catchment area and updated with population figures and developments
according to the Sumatra Spatial Model, with separate inputs for tourism. This means that
investments are calculated for the catchment population only. However, solid waste
intervention, especially treatment in landfills, is generally organised at a higher
administrative level, in which several kecamatans can make use of one landfill and
collection trucks can service several desa or keluhuran. Therefore, the interventions have
been assessed at a somewhat higher level than for wastewater management. As a result,
the solid waste interventions are clustered and individual measures cannot be directly
assigned to individual desa or keluhuran. Furthermore, in practice most solid waste
interventions will also service nearby non-catchment population. However, any additional
cost required is not included in this assessment. More details on solid waste and its
management can be found in Annex N.1.
8.5.2.2 Investment scenarios
For solid waste three scenarios are considered; 1) an intermediate scenario that follows the national policy, 2) a low scenario that envisages a more realistic, slower, rate of implementation, and 3) an accelerated scenario that reaches 100% coverage by 2022. Table 8.12 shows for each of the scenarios the access to domestic waste collection and disposal or 3R facilities. The next table, Table 8.12, presents the investment costs for the three scenarios. For the current situation that is mainly characterized by informal collection, zero coverage is assumed.
Table 8.12, Access to solid waste disposal facilities and services according to four scenarios. Scenario A
Baseline
Scenario B
Low
Scenario C
Intermediate
Scenario D
High
2018
Final disposal and
3R facilities
Collection activities
0%
0%
0%
0%
0%
0%
0%
0%
2022
Final disposal and
3R facilities
Collection activities
0%
0%
10%
11%
12%
12%
100%
100%
2042
Final disposal and
3R facilities
Collection activities
0%
0%
95%
93%
95%
93%
100%
100%
Improvements could be made with commitment from regional leaders, aiming at improving
solid waste management to support tourism in Lake Toba. The province could lead the
development of a regional waste management program, together with the seven districts
directly draining into the lake.
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Table 8.13, Overview of estimated investment costs for the period 2018-2022 to reduce nutrient loads from
solid domestic waste (including tourism) into Lake Toba, in low, intermediate and high investment
scenarios.
B. Low C. Intermediate D. High
CAPEX OPEX* CAPEX OPEX* CAPEX OPEX
Infrastructure
Final disposal and
3R facilities 106,000 18,112 120,000 20,696 295,000 135,756
Collection activities 5,000 62,915 8,000 71,271 113,000 472,554
Institutional,
information
(included in OPEX)
Subtotal 111,000 81,027 128,000 91,967 408,000 608,310
Reserved 111 81,025
111 81,025 111 81,025
Extra investment
required (million
IDR) 110,889 2 127,889 10,942 407,889 527,285
Total (million IDR) 110,891 138,831 935,174
US$ equivalent
(000, split) 8,217,025 141 9,476,751 810,811 30,225,176
39,072,61
2
US$ equivalent
(000, total) 8,217,166 10,287,562 69,297,788
8.5.3 Erosion reduction
8.5.3.1 Background
Lake Toba’s water quality has been decreasing because of changing land use patterns.
Conversion of forest cover, with associated illegal logging and fires, is an unsustainable
practice. In addition, Toba stream water and surface runoff have stimulated algal growth.
Erosion control, forest rehabilitation, and better land-use management are therefore critical
to maintain the health of Lake Toba. The Save Indonesian Lake Movement (‘Germadan’)
in 2009 for Lake Toba attempts to review all the regulations related to Lake Toba and
analyses the gaps in the overall management of Lake Toba, including its surroundings
(section 3.4). The Ministry of Environment and Forestry, together with the Provincial Forest
Service, is now implementing a reforestation program. More details on erosion reduction
can be found in Annex N.2.
8.5.3.2 Investment scenarios
Several interventions would reduce erosion in Lake Toba’s catchment area. Below various suggestions are made, some of which would have optimal effects, while others can be considered the bare minimum. In Table 8.14 these are summarised with approximate costs and an indication of total budget for each of the two scenarios.
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Natural infrastructure approaches can mitigate and prevent further damage in watersheds.
In addition to conducting natural restoration, building several simple structures can go a
long way in the effort to reduce erosion. Examples of these are containment dam and gully
plugs in the upper watershed, controller dam and terraces in the central part of the
watershed, and infiltration wells in the lower watershed. Such structures could help prevent
natural disasters (floods and landslides) and protect vital buildings located downstream.
Another way of reducing erosion is by introducing more trees in the landscape through
social forestry and agroforestry. In support of this, agro-industry and agro-tourism could
be introduced with strong community involvement, encompassing all parts of the value-
chain. This will help to improve people’s livelihoods while reducing the extent of critical and
degraded lands. Support from agricultural extension services is required to encourage
local communities to adopt best planting practices and avoid detrimental impacts of
fertilizers and business-as-usual planting practices. This can help a transition towards
more sustainable agriculture that has the potential to halt and even reverse erosion instead
of causing it. Such processes require the further strengthening of both the regulations and
institutional aspects of restoration.
Monitoring can be strengthened by applying the free global database and interactive
mapping tool of Global Forest Watch Water (GFW Water). This tool can help stakeholders
to apply natural infrastructure as one of their strategies to enhance water security and
improve watershed management.
Table 8.14, Summary of measures for erosion control and total costs of two different scenarios.
Measure Costs
Best
scenario
Minimal
scenario
Infrastructure
a. Natural infrastructure
(reforestation)
1,150
US$/ha
x
b. Erosion control structures x
c. Restoration of degraded lands x
Institutional
d. Develop agro-industry and agro-
tourism
x
e. Promote best planting practices 859 US$/ha
f. Strengthen regulations and
institutional aspects
x
Information
g. Adapt GFW Water x
h. Monitor land-use conversion x
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8.6 Cumulative impact of scenarios
8.6.1 Four scenarios
The potential impact of the scenarios has been elaborated for the main sources
aquaculture, livestock and domestic wastewater in the sectios above. This section
evaluates the cumulative impact of the four combined scenarios on nutrient loads and
long-term concentrations. The scenarios are summarized in Table 8.1, while Figure 8.1
gives an overview of the four compartments.
The nutrient loads and concentrations resulting from the four combined scenarios are
presented in the following figures for the whole lake and four compartments. The displayed
concentrations represent equilibrium concentrations on the basis of input data for 2018,
2022 and 2042. It may take tens of years to achieve each of these equilibrium states
(Figure 7.13). Limits for oligotrophic and mesotrophic state have been indicated for
phosphorous at 10 and 30 μg/l respectively, and for nitrogen the 350 μg/l oligotrophic limit
is displayed (based on Nürnberg, 1996; Table C.2 in Annex C.3). Figure 8.12 shows the
results for the whole lake, Figure 8.13 for the northern compartment, Figure 8.14 for the
southern compartment S1, Figure 8.15 for the southern compartment S2, and Figure 8.16
for the southern compartment S3. The graphs show loads and concentrations by
compartment at fixed scales to enable comparisons between compartments.
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Figure 8.12, Projected impacts of four intervention scenarios (summarized in Table 8.1) on total loads and resulting long-term concentrations of nitrogen (left) and phosphorous
(right) for the whole of Lake Toba.
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Figure 8.13, Projected impacts of four intervention scenarios (summarized in Table 8.1) on total loads and resulting long-term concentrations of nitrogen (left) and phosphorous
(right) in the northern compartment (according to Figure 8.1) of Lake Toba.
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Figure 8.14, Projected impacts of four intervention scenarios (summarized in Table 8.1) on total loads and resulting long-term concentrations of nitrogen (left) and phosphorous
(right) in the southern compartment S1 (according to Figure 8.1) of Lake Toba.
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Figure 8.15, Projected impacts of four intervention scenarios (summarized in Table 8.1) on total loads and resulting long-term concentrations of nitrogen (left) and phosphorous
(right) in the southern compartment S2 (according to Figure 8.1) of Lake Toba.
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Figure 8.16, Projected impacts of four intervention scenarios (summarized in Table 8.1) on total loads and resulting long-term concentrations of nitrogen (left) and phosphorous
(right) in the southern compartment S3 (according to Figure 8.1) of Lake Toba.
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Without any interventions (scenarios A and B), nutrient concentrations will continue to rise,
leading to a long-term eutrophic state in the northern and southern compartment S1 for
phosphate and mesotrophic for nitrogen. The southern compartments S2 an S3 would remain
mesotrophic for phosphorous and oligotrophic for nitrogen. Substantial reductions in nutrient
loads, concentrations and trophic state can only be achieved in the two scenarios with reduction
of aquaculture: the intermediate C and high D scenarios.
For nitrogen (N), compartments S2 and S3 would remain oligotrophic in all scenarios. In the
northern compartment, increased loads under scenarios A and B would result in long-term
concentrations above the oligotrophic limit of 350 µg/l. This is mainly because of the loads from
aquaculture (Table 8.6 and Figure 8.5). In the smallest southern compartment S1, only scenario
D would lead to long-term concentrations below the limit for oligotrophic state, and scenario C
in 2042, with a maximum aquaculture production of 10,000 tons/year.
For phosphorous, the situation is different. For the lake as a whole, none of the scenarios would
eventually lead to an oligotrophic state. However, the effects differ significantly across the
compartments. In southern compartments S2 and S3, phosphorous loads from 2022 onwards
in scenario D would eventually bring the total phosphorous concentrations from a mesotrophic
level down to just below the oligotrophic limit of 10 µg/l. This means that if scenario D is
adopted, eventually oligotrophic water will flow out from compartment S3 into the Asahan River
to downstream users. Concentrations in the northern compartment N would slowly go down
below the limit for a mesotrophic state, based on the loads in 2022 and 2042 in scenarios C,
and all years in scenario D.
Compartment S1 is the smallest and also the most problematic in terms of water quality.
Because of the intensive use with high population densities and livestock, the loads lead to very
high long-term concentrations. In scenario C and D aquaculture is halted completely, but loads
from livestock and wastewater each bring the long-term phosphorous concentration to levels
above the oligotrophic limit of 10 µg/l (Figure 8.7 and Figure 8.11). Combined, these loads lead
to a long-term mesotrophic state for phosphorous, even under scenarios C and D.
Only when mitigating measures in all sources: aquaculture, livestock and domestic loads are
applied, under the high scenario D, can the oligotrophic limit eventually be reached in
compartments S2 and S3. For the lake as a whole and in the northern compartment, the
mesotrophic limit will be feasible. For compartment S1 additional measures will be needed.
8.6.2 Alternative scenario
Interventions in aquaculture and livestock manure management have high impacts on nutrients for relatively low investment costs when compared to wastewater management. Investments in sanitation facilities are expensive and have limited impacts on nutrient loads and resulting long-term concentrations. An alternative scenario E combines high investments in aquaculture and livestock manure management with an intermediate level of investment in wastewater (Table 8.15).
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Table 8.15, Three scenarios to reduce nutrient loads into Lake Toba.
Driver Scenario C
Intermediate
Scenario D
High
Scenario E
Alternative
Aquaculture
Gradual reduction of
production
Rigorous reduction of
production
Rigorous reduction of
production
2018
2022
2042
64,000 tons, FRC 1.9
50,000 tons, FCR 1.9
10,000 tons, FCR 1.9
64,000 tons, FRC 1.2
10,000 tons, FCR 1.2
10,000 tons, FCR 1.2
64,000 tons, FRC 1.2
10,000 tons, FCR 1.2
10,000 tons, FCR 1.2
Livestock Conversion of manure into biogas
2018
2022
2042
1% conversion
20% conversion
40% conversion
5% conversion
30% conversion
60% conversion
5% conversion
30% conversion
60% conversion
Wastewater
Implementation as
planned
Accelerated
implementation
Implementation as
planned
2018
2022
2042
On-site: 50%
On-site: 85%, Central: 2%
On-site: 94%, Central: 6%
On-site: 50%
On-site: 69%, Central:
31%
On-site: 50%, Central:
50%
On-site: 50%
On-site: 85%, Central: 2%
On-site: 94%, Central: 6%
Tourists
per year
Best case Best case Best case
2018
2022
2042
1,802,200
2,212,000
3,410,300
1,802,200
2,212,000
3,410,300
1,802,200
2,212,000
3,410,300
The impacts of the alternative scenario E on the total phosphorous and nitrogen loads are
compared to the intermediate scenario C and high scenario D in Figure 8.17. Subsequently,
the nutrient loads and concentrations resulting from these three scenarios in the four
compartments are presented in Figure 8.18. These graphs show loads and concentrations by
compartment at different scales to enable a closer look and comparison between scenarios in
each compartment. The displayed concentrations represent equilibrium concentrations on the
basis of input data for 2018, 2022 and 2042. It may take tens of years to achieve each of these
equilibrium states (Figure 7.13). Limits for oligotrophic and mesotrophic state have been
indicated for phosphorous at 10 and 30 μg/l respectively, and for nitrogen the 350 μg/l
oligotrophic limit is displayed (based on Nürnberg, 1996; Table C.2 in Annex C.3).
Figure 8.17 shows how the loads of aquaculture (in blue) and livestock (in red) in the alternative scenario E are similar to those in the high scenario D, while domestic wastewater (in green) is relatively higher, as in intermediate scenario C. In Figure 8.18 the resulting long-term concentrations of the alternative scenario E stay close to those of high scenario D, except for compartment S3, and for nitrogen also in S1. Compartment S3 is the only place where the alternative scenario E leads to long-term phosphorous concentrations that would change the eventual end-state, from oligotrophic to mesotrophic.
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Figure 8.17, Nutrient loads of total nitrogen (top) and total phosphorous (bottom) resulting from three different
scenarios to reduce nutrient emissions from aquaculture, livestock manure and wastewater, in Lake Toba as
a whole.
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Figure 8.18, Projected impacts of three intervention scenarios (summarized in Table 8.15) on total loads and
resulting long-term concentrations of nitrogen (left) and phosphorous (right) across four compartments
North, S1, S2, and S3 of Lake Toba.
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9 Response: water quality monitoring
9.1 Three pillars
The design of effective monitoring programs is based on three pillars that are of equal weight
(Buijse and Noordhuis, 2012; Figure 9.1). These are the following:
1. System knowledge. The workings of the lake ecosystem dictate what, where and when
monitoring should take place. Also, the system links connected to the issue(s) that prompt
the monitoring, such as eutrophication, determine what should be monitored.
2. Needs: the focus or the management decision (for which the data provides the basis).
The issues (impacts in terms of DIPSR) at hand or the policy questions are the second
determinant for the focus of the monitoring program. For example, the focus can be to only
receive a ‘signal’ when something is wrong in the system. The focus can be to monitor
progress of implemented policies. Alternatively, the focus can be to gain system knowledge.
All these examples of focus lead to different monitoring programs with different monitoring
intensities.
3. Technical monitoring possibilities. The available monitoring technology determines
what can be measured, at what level of accuracy and at what costs.
Figure 9.1, The three pillars needed to formulate a monitoring plan (source: Deltares).
These three pillars need to be defined clearly and in multi-stakeholder processes by all relevant
stakeholders, before all aspects of the monitoring plan can be defined and elaborated.
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9.1.1 System knowledge
As an example of the system knowledge needed for Lake Toba, the process of eutrophication
is crucial. In the simple causal diagram in Figure 9.2, the causes and effects of eutrophication
are shown. Based on this diagram, it is relatively easy to pick crucial parameters to monitor
eutrophication. First, changes in the concentration of nutrients and primary producers seem the
most important (central) parameters for the signal function. Secondly, in case people want to
predict potential problems, the monitoring of the causes and effects will provide insight under
what circumstances the (negative) effects will occur. Clearly, the second objective will lead to
more parameters to monitor. For monitoring purposes, all relevant stakeholders, both outside
and within organizations should have the same understanding of the ecosystem functioning.
Making a causal diagram is crucial to identify and agree on important monitoring parameters.
Figure 9.2, The causal diagram of eutrophication (source: Chapman, 1996).
The external link in the cause and effect figure links the lake system to its surrounding catchment. Therefore, in addition to the conceptual knowledge model of the lake system, a
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conceptual model on the catchment scale is also crucial to determine monitoring needs and most importantly, a common understanding and consensus among the stakeholders as to why certain system and monitoring aspects are important. In Figure 9.3 a conceptual model of a catchment system is given.
Figure 9.3, Conceptual model of a catchment (Lehr et al., 2005). A similar model can be made for the Lake Toba
catchment to underpin the monitoring choices made.
9.1.2 Information needs
The analysis in this report, as part of the water quality roadmap for Lake Toba, focused on
phosphate, and to a lesser extent nitrogen, as main determinants of eutrophication. Other
parameters may be relevant in this process as well, such as Biochemical Oxygen Demand
(BOD). Moreover, other water quality issues might play a role at Lake Toba, with potentially
important local impacts on, for instance, the aquatic ecosystem and even human health, such
as inorganic compounds, pesticides and pathogens. These would need to be considered as
well in an overall monitoring plan.
PJT1 recently measured increased values for BOD and COD between May 2016 and July 2017
at several locations (Table G.1). These results, together with the measured decrease in
dissolved oxygen indicate that the quality of Lake Toba’s water has further decreased. In a
future monitoring program, sampling points should be added close to the pollutant sources to
better understand the nature, extent, and potential degradation of the pollutant loads into Lake
Toba. This will make it easier for stakeholders to analyze the various causes of decreasing
water quality in Lake Toba.
To improve understandings about Lake Toba’s system, better meteorological data are required.
The meteorological station at Medan airport is 80 km North of Lake Toba whereas the mountain
range and the ridge of the caldera shield the lake from direct influence of wind. Therefore, two
on-lake meteorological stations preferably with on-line internet connection, one in the central
basin north and the other in the central basin south of Samonsir peninsula would greatly reduce
the uncertainty on the physical conditions and analyses of events such as shown in Figure 6.20.
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The hydrology and water balance of Lake Toba may at least hint at potential water sources
explaining the lake’s cooler deep water. To improve the hydrothermal analysis (especially with
respect to upwelling events) more information on these sources may be required.
Furthermore, the observation of dissolved gases, such as CO2 and CH4 and their sources, is
recommended as these gases may be introduced through ground water flows in this region
with active volcanoes as well as by bacterial fermentation. Possibly this may be enhanced by
more recent wastewater discharges into the lake and possibly unused fish food as well. In case
of high concentrations of dissolved CO2 this gas may reduce the lake’s stability, such as with
turn over events, as in Lake Nyos in Cameroon, WestAfrica, whereas CH4 would enhance its
stability.
Development of a dynamic model as a long-term goal would ensure good and consistent monitoring. This would need to be combined with a clear definition of the parameters that need to be monitored.
9.1.3 Technical capabilities
The institutes currently involved in water quality monitoring (see section 3.3), each have a role
to play in a future monitoring plan for Lake Toba, based on its mandate, technical capabilities
and financial possibilities.
• DLH-SU (22 sampling sites) is specialised in the signal function, general monitoring of
long term trends in lake status, with a focus on parameters near the shore.
• LIPI is specialised in exploratory and scientific monitoring, aimed at understanding the
lake’s functioning. Its 12 sampling locations are all in the middle in the lake, including
depth profiles, to further develop their 3D hydro-dynamic model.
• PJT1 is in a unique situation because of its mandate supported by Presidential Decree
2/2014, of being able to collect revenues for lake management. This supports their
financial ability to sustain a monitoring program. Its plans to construct a water quality
laboratory near Parapat are in an advanced stage and additional funding is sought to
accelerate the development process. They now have 20 sampling locations for water
quality monitoring, including one in a non-polluted area, as a reference point (Figure 3.4).
• PT Aquafarm Nusantara (PTAN) offers additional sampling sites near the major fish
farms.
A more detailed inventory of the technical capabilities and limitations of these main water quality
monitoring institutions and identifying comparative advantages of each, are among the first
activities of the monitoring working group (section 9.2). These are necessary first steps towards
combining the sampling sites into one comprehenvsive sampling and monitoring plan and
program.
9.1.4 Incorproating remote sensing capabilities
Remote sensing has been shown to be a powerful, feasible and relatively low-cost tool,
complementing in-situ water sampling, as part of comprehensive water quality monitoring.
Remote sensing data, for the most part, are open and free. However, the processing chain
requires development and periodic validation with ground reference data to get an accurate
representation of biogeochemical dynamics. Remote sensing enables unique insights into
spatial and temporal dynamics, but challenging atmospheric conditions in the tropics require
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maximizing satellite overpass coverage, thus combining several multispectral sensing
platforms is required to achieve an optimal result, i.e., (i) high-resolution (e.g. Sentinel-2A/2B,
Landsat-8); (ii) moderate-resolution (e.g. MERIS, S3A OLCI); and (iii) low-resolution
geostationary (e.g. Himawari-8).
Using high-resolution sensors like Sentinel-2 / Landsat-8, the revisit frequency will more than
double to less than a 5 day revisit (from ~10 days) due to Sentinel-2B data ramp-up by year-
end 2017. With this, and assuming atmospheric conditions similar to the last several years,
more than 5 to 8 cloud-free images per year can be expected.
In addition, Sentinel-3A, Sentinel-3B launches are scheduled for Q1 2018 with daily Ocean and
Land Color Instrument (OLCI) revisits. Also, five multi-spectral sensors will soon be online for
enhanced temporal coverage of Lake Toba, as follows: • 3 High spatial-resolution (Sentinel-2A + 2B, Landsat-8), enabling to fingerprint lake
surface and water-quality dynamics on a monthly to seasonal basis • 2 Moderate-resolution (S3A OLCI + S3B planned 2018), with daily to weekly dynamics
and long term continuity, multi-year / decadal monitoring (MERIS time-series).
Further optimization of the constant-threshold (CTR) filtering or masking of data based on
SWIR/NIR bands is needed to remove atmospheric (haze/clouds/marine layer) and optical
artifacts (glint), and to improve quality and quantity of valid pixels.
Benefits of higher remote sensing data sampling rates from lower-resolution sensors, such as
ESA MERIS, were demonstrated to overcome atmospherically-clear pixel availability and
generate high-value product maps and movies. Integration of these instruments (NASA
Aqua/Terra MODIS and ESA Sentinel-3A/3B OLCI) would be key part of comprehensive
monitoring strategy going forward.
9.1.5 Requirements
It is recommended to start by designing a monitoring program without taking the costs into
account. After the “ideal” monitoring program (for the predetermined focus) is composed, it can
be optimised for minimum costs and maximum benefits. Only in this order will it become clear
what cutting costs means for the results of the monitoring program. Sometimes cutting costs
without taking into account each of the three pillars can result in an ineffective or even useless
program.
In case the monitoring program is carried out in collaboration by multiple partner organizations,
the development and reasoning behind the monitoring program should be clear for all partners.
Preferably, the program is developed in a collaborative stakeholder process to make sure all
the perspectives are included, and changes that are made during the program will not affect
the overall anticipated result.
A central data storage and retrieval system is required to ensure availability of the data, and
consistency across time and stakeholders to make sure they base their analysis and decisions
on the same data. It is important to involve the future users and monitoring stakeholders at an
early stage. Likewise, the identification of a dedicated organization that will host the data
storage system is crucial, so that agreements on data ownership and access can be made
clear to all stakeholders from the beginning.
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9.1.6 Data collection: Common sources of error Chapman (1996) lists common sources of error and appropriate actions in water quality assessment. His table is provided here as practical checklist for monitoring studies (Table 9.1). The International Organization for Standardization (ISO) sets more elaborate standards for water quality monitoring, including sampling procedures and laboratory analyses in ISO standard 5667, parts 1 to 24, and for water quality laboratories in ISO standard 17025 (www.iso.org). Basically, most of the errors can be overcome by setting up standard field and laboratory protocols for monitoring. When contracting sub-contractors for the monitoring, these standard protocols should be included in the Terms of Reference. Important recommendations following from this table are summarised in the next paragraph.
Table 9.1, Some possible sources of errors in the water quality assessment process with special reference to
chemical methods (adapted from Chapman, 1996). For more details on ISO 5667 and ISO 17025, see
www.iso.org.
Assessment step Operation Possible source of error Appropriate actions
Monitoring design Site selection Station not representative (e.g. poor mixing in rivers)
Preliminary surveys
Frequency determination
Sample not representative (e.g. unexpected cycles or variations between samples)
Field operations Sampling Sample contamination (micropollutant monitoring)
Decontamination of sampling equipment, containers, preservatives
Filtration Contamination or loss Running field blanks
Field measurement Uncalibrated operations (pH, conduct., temperature)
Field calibrations, Replicate sampling
Inadequate understanding of hydrological regime
Hydrological survey
Sample shipments to laboratory
Sample conservation and identification
Error in chemical conservation
Field spiking
Lack of cooling Appropriate field pretreatment
Error in biological conservation
Error and loss of label Field operator training
Break of container
Laboratory Pre-concentration Contamination or loss Decontamination of laboratory equipment and facilities
Analysis Contamination Quality control of laboratory air, equipment and distilled water
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Assessment step Operation Possible source of error Appropriate actions
Lack of sensitivity Quality assurance tests (analysis of control sample; analysis of standards)
Lack of calibration
Error in data report Check internal consistency of data (e.g. with adjacent sample, ionic balance)
Computer facility Data entry and retrieval
Error in data handling Checks by data interpretation team
Interpretation Data interpretation Lack of basic knowledge Appropriate training of scientists
Ignorance of appropriate statistical methods
Omission in data report
Publication Data publication Lack of communication and dissemination of results to authorities, the public, scientists.
Setting of goals and training to meet the need of decision makers
9.2 Monitoring working group
The primary recommendation is to start with selecting a monitoring working group based on
stakeholders who already are involved in monitoring and/or heavily depend on monitoring water
quality data. Devising such a plan should take no more than 6 months. The plan may be revised
when additional information needs, monitoring techniques, or new system aspects arise that
require adaptation of the monitoring effort. The investments needed to set up an integrated
water quality monitoring plan are detailed in Table 9.2 for a minimal scenario. The costs are
expert opinions based on personnel, commercial laboratory analyses and equipment costs.
Staff time of local experts is set at a flat daily rate of US$ 200. Laboratory costs combine capital
and operational expenses into unit prices as per common practice for water analyses. As a first
step towards implementation of this plan, the monitoring working group should start by
assigning responsibilities and filling in the lead actor for each activity, based on their capacities
and current activities.
Table 9.2, Investment costs for the development of an integrated water quality monitoring plan (time investment).
Description Output Investments (US$)
Time (days)
Setting up working group, setting goals, dividing tasks between monitoring actors. Product: workplan for developing a monitoring plan
1 meeting and workplan description
1,000 5
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Description Output Investments (US$)
Time (days)
Chapter I: Update existing conceptual catchment and lake system description. Find consensus among stakeholders over system concepts.
1 meeting and written chapter
4,000 20
Chapter II: What questions / information needs does the monitoring need to serve?
2 meetings, interviews and written chapter
4,000 20
Chapter III: Inventory of existing monitoring programs and operational technology present among stakeholders
1 meeting, gather and rank information
2,000 10
Chapter IV: Link chapters I, II and III. List system parameters to be monitored. Ideal spatial distribution and frequency of monitoring. Show types of data and pilot graphs and how these fulfil the information needs
1 meeting, example analysis based on existing or example data.
4,000 20
Chapter V: Operational program. Divide monitoring tasks over existing actors. Who does what? Show final budgets
1 meeting. Writing chapter
2,000 10
Chapter VI: Information management. Write down data and information procedures, data ownership, central database
Writing chapter 2,000 10
Chapter VII: Open community. What can be contributed by citizen science (mapping fish cages, reporting algal blooms)
Writing chapter 1,000 5
Chapter VIII: Describe existing links to scientific community, present common research goals and plan
Writing chapter 1,000 5
Closing presentation
Presenting to stakeholders
200 2
Total costs for devising a monitoring plan (US$)
21,000 105
The table shows the rough contents of the monitoring plan, the actions and approximate time
needed to write the chapters. This estimate is based on the assumption that the systems,
information needs and technology approach as described in previous paragraphs is followed.
Important elements for a comprehensive and successful monitoring plan are the following:
• Chose a central monitoring actor or coordinating body (for instance Brantas - PJT1 as the
coordinator in an arranged MoU with DLH and BWS Sumatera II):
o Both DLH-SU and BWS Sumatera II already have the responsibility to carry out
quantity and quality monitoring in Lake Toba. PJT1 has recently started water
quality monitoring. PJT1 is allowed to collect fees for the management of the lake,
and as part of the management plan they also have a financing plan, similar to the
plans which they also have in the other basins. One of these actors could be a
central data manager or a coordinating body could be appointed and empowered
by MoUs between PJT1, DLH-SU and BWS Sumatera II.
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• Chose and empower central data manager.
• Open community: Lower bariers for exchange of data:
o PJT1, DLH, BMKG currently have implemented data policies. Follow these data
policies and if needed devise additional open and transparent regulations on data
exchange, especially to crucial stakeholders and the scientific community.
o Agreement on sharing the data in this Roadmap, for instance in a central database.
This could be the first step towards a more formal data sharing mechanism. BWS
Sumatera II has already agreed to data sharing.
• Long term budget linked to plan.
• Open community: foster links to scientific community:
o To foster links to scientific community links between LIPI, PusAir, other institutes,
universities and international partners can be strengthened. This ensures new
insights and linking to research and education ensures future inflow of well-
educated river and lake managers.
• Use data to improve existing and new models (such as LIPI):
o The system models as developed by LIPI are very useful for future impact analysis.
However, these models need data for calibration and verification. Data needed for
development and calibration of detailed models are: hourly temperature, rainfall,
wind and wind direction, and depth profiles of temperature (T) and dissolved oxygen
(DO). And a good temporal (weekly/monthly) and spatial dataset on the modelled
parameters, such as P, N and chlorophyll (algal) concentrations, will also be created
across depth gradients.
• Include local stakeholders, for example with local knowledge (such as mapping fish cages,
reporting algal blooms).
o Possible options to connect to and gather information from lake users could be an
online system or a mobile application for tourism, such as send and receive
swimming water conditions, fisher folk (send and receive info on algae bloom,
oxygen condition), water supply (water intake/swimming water conditions).
o Local communities can also ‘adopt’ new monitoring facilities, such as sensors or a
mesh network.
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9.3 Monitoring parameters While the selection of critical parameters, sampling locations and frequency of sampling needs to be determined by the stakeholders as part of the monitoring plan, a first list of variables can be compiled to guide the process (Table 9.3). The list is based on Chapman’s monitoring guidelines (1996; Table K.3) adapted to Lake Toba: • Signal function (minimum investment) – sample variables for background monitoring
monthly; • Exploratory function (intermediate investment): same as statistic but lower frequency for
expensive analyses; • Statistic function (no budget constraints) – sample variables for background monitoring
plus for aquatic life & fisheries plus for recreation and health weekly.
All monitoring scenarios take 40 sampling locations, combining the best sites from the existing 28 of DLH-SU, 12 of LIPI and 20 of PJT1. Some of these are close together and could be combined. The number and locations of sampling sites should be gradually implemented and evaluated every year. In addition to the parameters that are indicative of the in-lake water quality (Table 9.3), a second set of parameters is proposed in Table 9.4 for background and depth profiles. In the medium term (5-10 years), some of the sampling points could be developed for real-time online monitoring. In Table 9.3 prices per sample have been used to account for differences between laboratories and support separate calculations for signal, exploratory, and statistic monitoring, as well as for depth profiles (Table 9.4). Once the total budget has been secured, it could be used to equip a dedicated laboratory at Lake Toba and support sampling processes by the various institutions. Table 9.3, Frequency of sampling for in-lake water quality variables (based on Chapman, 1996, see Table K.3) for a signal, exploratory and statistical function at Lake Toba (40 sampling sites) with the price per sample.
31 The price per sample includes capital and operational expenses as per usual practice of commercial laboratories.
Frequency / Month Unit price/sample31
(IDR) Signal Exploratory Statistic
General parameters
Temperature 1 4 4 52,990
Colour 1 4 4 148,372
Odour 4 4 52,990
Suspended solids 1 4 4 211,960
Turbidity/transparency 1 4 4 127,176
Conductivity 1 4 4 105,980
Total dissolved solids 4 4 211,960
pH 1 4 4 52,990
Dissolved oxygen 1 4 4 105,980
Hardness 4 4 190,764
Chlorophyll a 1 1 4 572,291
Nutrients 529,899
Ammonia 1 4 4 211,960
Nitrate/Nitrite 1 4 4 423,919
Phosphorous or phosphate 1 4 4 317,939
Organic matter
TOC 1 1 4 529,899
COD 1 4 4 476,909
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Table 9.4, Frequency of sampling for water quality variables (based on Chapman, 1996; see Table K.3) for a signal, exploratory
and statistical function for background and depth profiles.
Background monitoring Depth profiles
General parameters
Temperature x x
Colour x
Suspended solids x x
Turbidity/transparency x x
Conductivity x x
pH x x
Dissolved oxygen x x
Chlorophyll a x x
Nutrients
Ammonia x
Nitrate/Nitrite x
Phosphorous or phosphate x
BOD 1 4 4 476,909
Major ions 1 4 4 317,939
Sodium 1 4 4
Potassium 1 4 4
Calcium 1 4 4
Magnesium 1 4 4
Chloride 1 4 4
Sulphate 1 4 4
Other inorganic variables
Fluoride 4 4 211,960
Boron 4 4 169,568
Cyanide 1 4 529,899
Trace elements 1 4 582,889
Heavy metals 1 4 317,939
Arsenic & selenium 1 4
Organic contaminants
Oil and hydrocarbons 1 4 847,838
Organic solvents PASSIVE SAMPLING 2,755,475
Phenols 1 4 635,879
Pesticides PASSIVE SAMPLING 1,907,636
Surfactants 1 4 0
Microbiological indicators
Fecal coliforms 4 4 370,929
Total coliforms 4 4 370,929
Pathogens 1 4 3,285,374
Dissolved gasses (CO2/CH4) 1 4 1,483,717
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Organic matter
TOC x
COD x x
BOD x x
Major ions
Sodium x
Potassium x
Calcium x
Magnesium x
Chloride x
Sulphate x
In addition to measuring the water quality parameters mentioned above, environmental
variables need to be monitored, such as the extent of aquaculture and livestock numbers, to
guide predictions and modelling efforts. An overview of the three investment scenarios is
presented in Table 9.5 and the total costs are summarized in Table 9.7.
Table 9.5, Overview of interventions in the three scenarios for water quality monitoring.
Signal Exploratory Statistical
Monitoring working group Monitoring plan Monitoring plan Monitoring plan
Water quality analysis in-
Lake
Table 9.3 and 9.4
Table 9.3 and 9.4
Table 9.3 and 9.4
River outflows - 10 River lake inflows,
monthly, background
package 2)
20 River lake inflows,
weekly, background
package 2)
Depth profiles 10 locations,
monthly, WQ
package depth
profile 2), 10 depths
per location
10 locations, weekly,
WQ package depth
profile 2), 10 depths per
location
20 locations, weekly,
package depth profile 2); 10 depths per
location
Passive samplers:
pesticides, (vet)medicines
- 10 locations, dry and
wet season
20 locations, dry and
wet season
Meteorology stations and
fixed sensors
2 online met
stations; 4
continuous online
depth profiles basic
WQ
4 online met stations; 8
online continuous online
depth profiles based
WQ
4 online met stations;
16 online continuous
online depth profiles
based WQ
mapping & surveys Survey of
aquaculture:
mapping locations,
supply chain sales,
stocking densities
Signal parameters +
mapping farmers
Exploratory
parameters + mapping
domestic interventions
Toba Research fund 1 PhD study 5 PhD studies 10 PhD studies
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9.4 Investment scenario
Based on the estimated requirements for sampling and the other elements of water quality
monitoring, three investment scenarios have been elaborated. A summary of the costs required
for water quality sampling is presented in Table 9.6. With the addition of costs for the working
group and the research fund, the annual costs for low, intermediate and high investment
scenarios vary from 20 to 92 billion Indonesian rupiah (Table 9.7). Total investment costs of a
minimal program would be IDR 102.2 billion (US$ 7.6 million) for the first five years from 2018
to 2022. A more ambitious intermediate program would cost a total of IDR 240.9 billion (US$
17.9 million), while an aspirational program would amount to IDR 461.1 billion (US$ 34.2 million)
for five years.
Table 9.6, Summary of sampling costs for three functions, corresponding to three investment scenarios, based on sampling frequency and unit prices in
Table 9.3. Annual costs
Signal Exploratory Statistical
General parameters 661 2,696 3,520
Nutrients 458 1,831 1,831
Organic matter 712 2,086 2,849
Major ions 153 610 610
Other inorganic variables
987 1,750
Trace elements
280 1,119
Organic solvents
712 2,849
Microbiological indicators
3,001 7,732
Dissolved gasses (CO2/CH4)
712 2,849
Total (million IDR) 1,984 12,915 25,109
US$ equivalent (000) 147 957 1,861
Table 9.7, Investment scenarios for an integrated water quality monitoring plan. The costs are expert opinions
based on personnel, commercial laboratory analyses and equipment costs. Minimal Intermediate High
Monitoring working group 280 561 1,966
Water quality analysis 1,984 12,915 25,109
Depth profiles 3,244 14,059 28,118
River outflows 228 1,977
Passive samplers 1,262 2,524
Meteorology stations and fixed sensors
(incl. CAPEX)
13, 513 16,323 27,027
Mapping & surveys 80 160 240
Research 1,338 2,676 5,352
Total (million IDR/year) 20,439 48,184 92,313
Total for 2018-2022 (million IDR) 102,195 240,920 461,565
US$ equivalent (000/year) 1,515 3,571 6,841
US$ equivalent for 2018-2022 (000) 7,573 17,853 34,203
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Table 9.7 shows direct costs for monitoring parameters that are not or incidentally monitored
at the moment. Moreover, the emission estimates depend on accurate statistical data of the
catchment, such as population numbers, livestock numbers, and fish production. These have
not been separately budgeted because it is an existing task for various government units.
Specific recommendations on the statistical data include the following:
• Certified data on amounts produced;
• Certified data on number of livestock per type at desa level;
• Number of livestock in what types of farms (small scale, large industrial scale);
• Locations of large-scale farms;
• Record waste water treatment facilities;
• Record licensed hotels, industries and other businesses.
Install on-lake meteorological stations that measure Temperature, rainfall, wind strength and
direction continuously, at least at four locations distributed across the lake (North, South, East,
West). An option could be to connect to weather forecasts already available in operational
databases and model DEWS/FEWS at BMKG. Costs are estimated at US$ 100,000 for each
site.
In anticipation of the monitoring plan the DLH-SU and LIPI monitorings locations could be
merged to achieve full coverage along the shoreline and mid-lake. The monitoring frequency
should increase to weekly for the upper epilimnion and can be monthly for depth profiles on
fewer locations. One could envisage in the monitoring plan a split between cheap and quick
manual variables gathered daily/weekly with a depth profile. Add more expensive variables that
are monitored monthly with a depth profile only for selected variables. These ‘trade-off’ choices
based on costs should be made during the development of the monitoring plan, in clear
coherence with the management information needed to monitor the state and to develop
system understanding.
In addition to the effort mentioned above, some variables can be monitored and data provided
online and on very high frequency and across a depth profile. These are T, DO, conductivity,
salinity.
In order to monitor the presence of possible toxic substances, a technique called ‘passive
sampling’ is useful and cost-effective. Passive samplers (such as silicon sheets) absorb the
micro pollutants during their deployment in water. They will absorb a time averaged (optimally
4 weeks) amount of the micro pollutants. Subsequently, these can be analysed in the lab for
pesticides, medicine (like antibiotics in aquaculture and human consumption) and hormones.
Hence only one single analysis will yield a time-averaged concentration of these pollutants.
Laboratory costs in a western laboratory are about US$ 4,000 in total for about 150 types of
substance.
The build-up of gasses (CO2 and CH4) can be a hazard for the local community. This is not part
of a monitoring plan, but can be researched by for example LIPI. Methane (CH4) in solution can
influence the lake stratification and as such is important to measure.
The use of existing telecommunication facilities can be integrated into the water monitoring
plan. The mobile network provides real time data relay from sensors and measuring stations to
a data server. According to the Tourism Report, PJT1 and others, the existing coverage of
telecommunication facilities around Lake Toba and core tourism areas is excellent, including
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internet and data services. In terms of service provision, TELKOMSEL has the best coverage,
with a stable connection and speed of data transfer, followed by ProXL and Smartfren.
TELKOMSEL and ProXL provide 4G connection. To support water quality monitoring purpose,
those providers could be contacted to discuss the best package or program for data transfer.
No specific investment is needed, other than a SIM card.
Data transmission to base stations should be included in the monitoring plan. If existing
connections are not reliable, there are numerous alternatives to 2G, 3G or 4G internet
connections. Specifically for lake monitoring, a LoRa mesh network could be set up with lake-
based fixed and on line systems (https://www.lora-alliance.org/technology). This is low cost
technology and these costs are negligible compared to other costs in this report.
Establishment of a remote sensing program in the future would allow specific questions about
Lake Toba water-quality, suspended particulates and algal-bloom dynamics. Regionally-tuned
models for Sentinel-2A+2B, Landsat-8 as well as MERIS / S3A / VIIRS will need to be
developed, integrating available in-situ sampling data. Such further efforts are summarized as
follows and (conservative) cost estimates for each item are provided in Table 9.8.
• refining spatial analysis using specific sampling locations and transects to better understand the noted changes in water-quality visible in ~mid 2005 (MERIS data) using additional data from MODIS (Aqua / Terra);
• performing focused multi-sensor analysis to determine specific conditions leading to the acute water-quality events of record (May 4, 2016 and Jan 9, 2017);
• refining atmospheric correction, glint, speckle and masks to improve data quality;
• incorporating processing of two new sensor platforms Sentinel-2B and Sentinel-3A (ramp-up completion expected by year-end 2017);
• defining a detailed remote sensing monitoring approach (specific sensors, processing chains and algorithm settings) as part of comprehensive water-quality management strategy.
Table 9.8, Summary of action items for remote sensing of water quality in Lake Toba
Action Item Cost Estimate (USD)
(1) Refinement of spatial data analysis $20,000
(2) Multi-sensor data analysis for acute water quality events (2016, 2017) $30,000
(3) Improving remote sensing data quality $20,000
(4) Incorporate new remote sensing platforms (Sentinel-2B and 3A) $30,000
(5) Develop approach for remote sensing data use as part of water quality
management strategy
$25,000
(6) Training of GOI personnel on the use of remote sensing methods and data
for water quality monitoring applications
$25,000
The cost estimate in the table above are one-time expenses required to develop and implement
a remote sensing monitoring strategy for the lake and its contributing watershed, and it is
estimated that this work can be carried out over a period of one year (or less). The costs of
operating such a program, for example, on an annual basis (for budgeting purposes) can be
estimated based on staff, institutional and other costs; this would be part of item (5) in Table
9.8.
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An additional recommendation is to build capacity in the use of remote sensing tools to
complement other efforts in water quality, or as a starting point for new efforts. This could be
done as part of a larger effort to advance the state of knowledge and application of remote
sensing for water resources assessments. In the case of Lake Toba, this would involve
developing a tailored training or capacity building activity such as item (6) proposed in Table
9.8, that would engage the corresponding stakeholders to assimilate remote sensing as an
additional tool to support water resources management in the lake and its surrounding
environment.
An important item moving forward is the incorporation of remote sensing observations into
water quality management tools being used in Lake Toba, and specifically water quality
modeling (Sumatera model) developed and in use fort the lake. Together with ground-based
observations and remote sensing data, a system to support decisions and investments in the
Lake Toba watershed should be developed and implemented, which will guide the evaluation,
prioritization and costing of measures and actions for lake water quality improvements.
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10 Summary results, conclusions and recommendations
The tourism sector in Indonesia is a promising growth sector that can provide inclusive
and sustainable opportunities for economic development. The archipelago is home to one
of the most biodiverse habitats in the world, having a rich array of tourism endowments
that form the underlying draw for visitors. Indonesia has expanded the offer and promotion
of its natural resources by increasing the size of protected areas and attracting more online
interest in natural activities. Despite this, Indonesia’s tourism industry is not operating at a
level consistent with the quality and diversity of its natural and cultural endowments, with
environmental sustainability being a key risk factor for the sector (WEF, 2017).
Four key constraints contribute to Indonesia not fulfilling its tourism potential. These
include: (i) continued poor access to, and quality of, infrastructure and services for citizens,
visitors and businesses; (ii) limited tourism workforce skills and private-sector tourism
services and facilities outside of Bali; (iii) weak enabling environment for private investment
and business entry; and (iv) poor inter-ministry/agency, central-local and public-private
coordination and weak implementation capabilities for tourism development in general,
and for monitoring and preservation of natural and cultural assets in particular.
In response, the Government has launched the Indonesia Tourism Development Priority
Program. For the implementation of the program, the GoI has decided to sequence the
development of tourism destinations, starting with three priority destinations: Lombok in
West Nusa Tenggara province; Borobudur-Yogyakarta-Prambanan in Central Java
province and the Special Region of Yogyakarta; and Lake Toba in North Sumatra province.
If developed effectively, these three distinctively different and unique destinations are
expected to increase their combined annual foreign and domestic visitor expenditures from
an estimated US$1.2 billion in 2015 to US$1.5 billion in 2021 and US$2.0 billion in 2026
(Horwath, 2017).
The objective of this report has been to prepare a Roadmap for Improving Water Quality
of Lake Toba as a Tourism Destination. It provides an understanding of the key drivers
leading to water quality issues along with costed investment scenarios associated with
specific investments aimed at reducing nutrient loads into the lake. These are intended to
inform preparation of an Integrated Tourism Master Plan to provide a stronger framework
for effective and sustainable tourism development.
Lake Toba is the largest volcano-tectonic lake in the world and one of Indonesia’s priority
tourism destinations. However, Lake Toba is largely a destination for local tourism with
declining appeal. With improvements in environmental sustainability, accessibility and
activities, Lake Toba can become an attractive destination for a wider variety of domestic
and international visitors.
This chapter summarizes the main findings of the study, with a focus on phosphorous (P),
the main determining factor of water quality in Lake Toba.
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10.1 Drivers of lake eutrophication
The most important aspect of water quality in Lake Toba is the amount of nutrients that
are dissolved in the lake. This is the “trophic state”. In contrast to other pollutants,
continuous pollution with nutrients (‘eutrophication’ by phosphorous and nitrogen) has the
potential to irreversibly affect the lake’s chemistry and biology on a system level. The water
quality of Lake Toba is under threat from eutrophication. Eutrophication is mainly driven
by nutrients from aquaculture (68% of total phosphorous load and 76% of total nitrogen).
Other contributors include livestock (19% of phosphorous and 5% of nitrogen) and
domestic wastewater (11% of phosphorous and % of nitrogen), shown in Figure 10.1.
Figure 10.1, Relative phosphorous loads into Lake Toba (P loads) from various sources for the whole lake.
10.2 Status and functioning of Lake Toba
Science informed policy measures have established the desired lake quality as
oligotrophic. The governor of North Sumatra issued decrees that indicate that the water
quality of Lake Toba should meet class I (raw water for drinking); and that the trophic state
of Lake Toba should be the natural state, being oligotrophic. In reality, based on available
data from monitoring sites scattered along shorelines, observed values show mesotrophic
status for phosphorous and oxygen profiles while nitrogen, chlorophyll and transparency
point to oligotrophic status but occasionally reach the mesotrophic as well. The
mesotrophic state leads to local effects such as algal blooms that harm the tourism sector.
Compared to data from 1930 (Ruttner, 1931), when the areas surrounding Lake Toba were
not yet affected by aquaculture, agriculture or forestry, the water quality in the lake has
decreased, both at the surface and at greater depths.
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10.2.1 Historical and current lake status
Monitoring water quality parameters indicate eutrophic states in Lake Toba ranging from
oligotrophic to mesotrophic. Table 10.1 presents an overview of the main conclusions on
the monitored parameters. The compartment model that predicts lake nutrient
concentrations has been calibrated to match monitored phosphorous and nitrogen
concentrations of 2015 by varying the retention rates of these nutrients in the model.
Ultimately, the modelled values for the year 2015 lie well within the ranges monitored in
the various compartments in the lake. Model results of LIPI suggest that local levels of
nutrient concentrations locally reach eutrophic levels, due to intense loading from sources
such as aquaculture. The conclusions below refer to long term average concentrations.
Due to the lake’s large size and long residence time, the effects of pollutant loads will
become visible over long time spans. Therefore present-day concentrations were
compared to concentrations measured in the 1930s. All monitored water quality
parameters have deteriorated since the 1930s both near the water surface and in deeper
water layers.
Table 10.1, Overview of present status of selected water quality parameters at Lake Toba: phosphorous,
nitrogen, chlorophyll-a, transparency, temperature and oxygen (based on data from DLH-SU, LIPI,
and PTAN).
Parameter Status in Lake Toba
Phosphorous Oligotrophic (2008-2012) to mesotrophic (2012-2016).
Phosphorous concentrations 1930: 0.005 mg/l; 2013: 0.01 PO4-P mg/l; 2016 peak: 0.05 PO4-
P mg/l.
Nitrogen Oligotrophic, mostly below 350 μg total nitrogen per litre, very occasionally above 650 μg/l.
Chlorophyll α
(algae)
Ultra-oligotrophic (till end 2014).
Mesotrophic (Feb-Aug 2016) with chlorophyll concentrations up to 12 µg/l.
Transparency Oligotrophic: 6m (Secchi depth highest 2009-2010: above 10m32); 1930s: 7.5-11.5 m
2016: algal bloom, sudden and drastic decrease, afterwards back to 6m.
Temperature Stable: between 25 and 28 degrees Celsius at water surface, stable for the last 10 years.
Temperature profiles and show clear stratification.
2016: peak over 28 degrees.
Oxygen Surface water concentrations constant in last 90 years, with peaks in 2006, 2007, 2016.
DO levels steadily decline as depth increases and remain the same beyond 200 meters.
Below 150 m in period 2008-2017: values below 0.5 mg/l; 1930s: 5.35-5.40 mg/l.
10.2.2 Lake functioning
To evaluate the effect of future developments on lake water quality, a general
understanding and agreement by stakeholders regarding the functioning of the lake is
important to produce useful calculations and widely supported policy recommendations.
To predict nutrient concentrations and subsequent eutrophication, the following factors on
lake functioning need to be considered for monitoring: lake vertical mixing or lake
stratification, horizontal mixing or hydraulic circulation and nutrient decay. The nutrient
loading, meaning the nutrient inputs to the lake by each source, is not a direct lake
characteristic but does require monitoring and quantification.
32 Lakes with Secchi depth above 10m do not qualify for ASC certification.
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The knowledge regarding vertical and horizontal water mixing in Lake Toba influences the
quantification of nutrient balance of the lake. Based on a comparison between modelled
and monitored chlorophyll concentrations, the default thermocline depth in Lake Toba is
estimated at around 50m, in line with observed thermal stratification data (PTAN, LIPI). As
a consequence, the pollutants emitted to the lake dissolve in the upper 50m water volume.
The water residence time in Lake Toba is around 80 years. Due to non-homogenous
mixing, this could be much longer for specific segments of Lake Toba. A long residence
time has the consequence that replacement of polluted lake water by clean inflows takes
a long time. Natural purification processes could be faster, but more research is needed
to determine whether this occurs in Lake Toba. It is important to note that a long residence
time makes an existing eutrophic state almost irreversible. Lake management of nutrients
is therefore of high importance and should start immediately.
Horizontal mixing determines the dispersion of pollutants entering the lake by rivers or
direct input. The shape of Lake Toba makes it unlikely that high pollutant loads in the North
will quickly reach the Southern part of the lake. However, in some of the current carrying
capacity calculations it is assumed that any pollutant entering the lake is immediately
dissolved in the total water volume of the lake33. This under-estimates the pollutant
concentrations occurring in the lake.
Monitoring data indicate lake stratification, oxygen depletion at greater depths and
fluctuations in stratification depth. The model-based analysis demonstrated that wind may
lead to bi-annual mixing and re-stratification events in the upper 10-20m in most of the
years. Deep mixing does not occur, explaining the lack of dissolved oxygen (anoxia) in the
deep layers (approximately >100m). Some upwelling of cooler water from deep layers
occurs, but these cooler waters do not arrive at the water surface (at least in the observed
period 2008-2016).
A zonal approach to modelling the water quality of Lake Toba provides new insights into
the functioning and drivers of water quality. Four theoretical compartments have been
defined based on topography and bathymetry. This includes one northern and three
southern compartments. These compartments provide a differentiated assessment of the
key drivers associated with water quality in Lake Toba. The compartment model that
predicts lake nutrient concentrations has been calibrated to match monitored phosphorous
and nitrogen concentrations of 2015 by varying the retention rates of these nutrients in the
model. Ultimately, the modelled values for the year 2015 lie well within the ranges
monitored in the various compartments in the lake. These can be further refined based on
a continuous process of improvement informed through better data. The results show
localised impacts requiring targeted strategies for the monitoring and management of
water quality interventions.
10.3 Water quality monitoring
10.3.1 Data assessment
The currently available data cover all aspects needed for an initial water quality
assessment and to construct simple effect models. There is no integrated monitoring
33 This is following current government regulations and therefore normal procedure in Indonesia
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program in which lake wide data were collected, stored and analysed over longer periods
of time. Data and their collection efforts were scattered among stakeholders. Datasets had
different levels of usefulness ranging from data to incidentally establish lake status to
(scarce) data with solid statistical validity. Field data are often low frequency data suited
to follow long term trends in status but usually have a frequency too low (years) or spatial
distribution too scarce to properly understand lake functioning. There appears to be no
mechanisms for systematic data quality control. Table K.4 presents an overview of the
various data and their characteristics.
The available water quality monitoring data are mostly included in reports and not as raw
data in digital form or as ‘open source’ data. When raw data are made available by
stakeholders, it is often in the form of Excel files. No centralized database has been
encountered.
The DLH-SU, LIPI and PTAN data were made available as raw data only to a limited
extent. Some data were supplied in the form of graphs only. PTAN data covered a
relatively high frequency consistent time series, while DLH-SU and LIPI covered larger
parts of the lake, albeit with lower or incidental monitoring frequency.
The DLH-SU data set is the most extended one of these three sources. With respect to
the required water quality parameters based on Chapman (1996), only a low number is
missing (hardness, conductivity, sodium, potassium, calcium cyanide, arsenic and
selenium, organic solvents, phenols, pesticides, surfactants). Probably, only the organic
contaminants (solvents, phenols, pesticides) are of any relevance to Lake Toba, compared
to the Chapman guideline. The PTAN and LIPI data sets are less ‘complete’ with respect
to their set of water quality parameters.
High frequency data (monthly or more) give more insight into lake functioning. Lower
frequency data (often at more locations) are useful for long term trends. In the quantitative
assessment of lake functioning, the PTAN dataset proved to be very useful. The dataset
covers a period of about 10 years at 4 locations near Samosir Island. The DLH-SU and
LIPI data, although of lower frequency, were useful as supporting data to verify whether
measured data values by PTAN were consistent across the lake.
To improve the analysis of lake stratification, better meteorological data are required. The
meteorological station at Medan airport is 80 km North of Lake Toba, whereas the
mountain range and the ridge of the caldera shield the lake from direct influence of wind.
Therefore, two on-lake meteorology stations, preferably with on-line internet connection
(hourly data at least), one in the central basin north and the other in the central basin south
of Samonsir peninsula would greatly reduce the uncertainty regarding the physical
conditions and analyses of events or anomalies such as shown in Figure 6.20.
The hydrology and water balance of Lake Toba hint at potential water sources explaining
the lake’s cooler deep water. To improve the hydrothermal analysis (especially with
respect to the upwelling events), more information on these sources is required. For this,
dissolved gases such as CO2 and CH4 and their sources need to be observed. In case of
high concentrations of dissolved CO2, this gas may reduce the lake’s stability with turnover
events, such as in Lake Nyos in Cameroon, West Africa. CH4 would enhance its stability.
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10.3.2 Towards a water quality monitoring plan for Lake Toba
For the design of an effective water quality monitoring program, three pillars are
important: 1) system knowledge, 2) information needs (with a focus on management
decisions), and 3) technical possibilities.
For pillar 1, the analysis in this report shows that eutrophication is the most important process threatening water quality in Lake Toba, for which various causes and effects should be monitored. Additional elements could be included as well to better understand lake functioning. In Table 9.3 and Table 9.4 in-lake water quality variables are listed, together with a suggested sampling frequency for a signal, exploratory and statistical function of Lake Toba. In addition to currently monitored parameters, dissolved gases such as CO2 and CH4 and their sources need to be monitored. In view of tourism and recreational water use, microbiological indicators such as coliform bacteria and pathogens need to be included in a regular monitoring plan as well.
System knowledge of Lake Toba can be further improved by development of a dynamic
model. This long-term goal can ensure consistent monitoring for quantitative analysis,
combined with a good definition of the parameters that need to be monitored.
The Reference Group and other stakeholders together shape the information needs (pillar
2), ideally by forming a dedicated monitoring working group. For the integration of data
collection, it is important to coordinate institutions, streamline methods, include spatial and
bathymetric stratification, and establish database management, preferably central and
open source. Collaboration between research centers, universities and other institutions
around Lake Toba is required for successful implementation of an integrated monitoring
program. This can be supported with a grant and research funding program.
For pillar 3, it is relevant to expand the technical monitoring capabilities. For lake
stratification: better meteorological data should be collected. Two on-lake meteorological
stations preferably with on-line internet connection, one in the central basin north and the
other in the central basin south of Samonsir peninsula would greatly reduce the
uncertainties on physical conditions. A LoRa mesh network could be set up to relay data
from sensors and measuring stations to a data server.
The investments needed to set up an integrated water quality monitoring plan and suggestions for monitoring efforts to be included in the plan, are summarised in Table 10.2, based on Table 9.2.
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Table 10.2, Summary of investment costs for an integrated water quality monitoring plan. Minimal Intermediate High
Monitoring working group 280 561 1,966
Water quality analysis 5,228 26,974 53,227
Other measurements 1,490 4,501
Meteorology stations and fixed
sensors (incl. CAPEX) 13,513 16,323 27,027
Mapping, surveys and
research 1,418 2,836 5,592
Total (million IDR/year) 20,439 48,184 92,313
Total for 2018-2022 (million
IDR) 102,195 240,920 461,565
US$ equivalent (000/year) 1,515 3,571 6,841
US$ equivalent for 2018-
2022 (000) 7,573 17,853 34,203
10.4 Water quality management
Various measures can be designed to reduce the nutrient load into Lake Toba and
stimulate natural purification processes. In the next sections, combined scenarios of
mitigating measures are proposed for those drivers that produce the highest loads of
nutrients: aquaculture, livestock and domestic wastewater. Additional measures on other
drivers may further reduce nutrient loadings and improve Lake Toba’s environment. A
rough indication of budget requirements has been added for various scenarios of
interventions.
10.4.1 Potential of interventions
Based on the relative inputs of nutrients, aquaculture (68% of total phosphorous), livestock
manure (19%) and domestic wastewater (11%) have been identified as the starting point
for mitigating measures. Individual measures are discussed in more detail below.
However, only when various measures are combined in an integrated approach can
effective reductions in nutrient loads be achieved. In chapter 8, four scenarios have been
introduced that were applied to each of the three major drivers of water quality. These
correspond to a baseline scenario for comparison and a low, intermediate and high
investment scenario, briefly summarized below. Table 10.3 shows an overview of the exact
numbers and percentages applied in each scenario.
Scenario A
This is the baseline scenario, without any interventions. For aquaculture the current
production level is maintained at 84,800 tons of fish per year with a Food Conversion Ratio
(FCR) of 1.9.
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Scenario B
This is the low scenario, with limited interventions in wastewater management. For
aquaculture, in absence of any measures, the production level is assumed to grow to a
maximum level of 106,000 tons with a Food Conversion Ratio (FCR) of 1.9. For
wastewater a slow implementation of the currently planned water and sanitation program
is assumed, in which the number of people with access to on-site sanitation (such as septic
tanks or latrines) increases from 0% in 2018 to 66% in 2022 and 94% in 2042.
Scenario C
This is the intermediate scenario, with interventions in aquaculture, livestock and
wastewater management. For aquaculture, the one remaining license is not renewed and
will expire naturally. There will be increasing pressure on fish farmers without licenses.
This will result in assumed production levels of 64,000 tons in 2018, 50,000 tons in 2022
and 10,000 tons in 2042. For the management of livestock manure, biogas conversion is
promoted, resulting in 1% conversion of manure into biogas in 2018, 20% in 2022 and
40% in 2042. For wastewater the currently water and sanitation program is implemented
as planned. Thus the number of people with access to on-site sanitation (such as septic
tanks or latrines) increases from 50% in 2018 to 85% in 2022 and 94% in 2042. In addition,
limited investments in off-site sanitation supply 2% of the population with a sewerage
system in 2022 and 6% by 2042.
Scenario D
This is the high scenario, the most optimistic one, with interventions in aquaculture,
livestock and wastewater management. For aquaculture, an active reinforcement policy
ensures that a production level of 10,000 tons is reached from 2022 onwards. In addition,
better feeding practices allow for a better food conversion ratio of 1.2. For the management
of livestock manure, biogas conversion is promoted more actively, resulting in 5%
conversion of manure into biogas in 2018, 30% in 2022 and 60% in 2042. For wastewater
the water and sanitation program is accelerated with additional funding. The number of
people with access to on-site sanitation (such as septic tanks or latrines) increases from
50% in 2018 to 69% in 2022 and then drops to 50% in 2042. In 2022 31% of the population
is connected to a central sewerage system, growing to 50% in 2042.
Figure 10.2 shows the impact of the combined scenarios on phosphate loads across the
four compartments. In the next sections, more detail is provided on the nature and broader
context of proposed interventions to reduce nutrient emissions into Lake Toba.
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Figure 10.2, Four investment scenarios with their impacts over time on the total total phosphorous (P) loads
into the whole Lake Toba (as one compartment). See Table 10.3Table 10.3 for an overview of the
applied input values.
Table 10.3, Overview of four investment scenarios to reduce nutrient loads into Lake Toba.
Driver Scenario A
baseline
Scenario B
low
Scenario C
intermediate
Scenario D
high
Aquaculture
Extrapolation
of current
situation
Growth to maximum Gradual reduction of
production
Rigorous reduction of
production
2018
2022
2042
848,00 tons
FCR 1.9
106,000 tons, FCR 1.9 64,000 tons, FRC 1.9
50,000 tons, FCR 1.9
10,000 tons, FCR 1.9
64,000 tons, FRC 1.2
10,000 tons, FCR 1.2
10,000 tons, FCR 1.2
Livestock Extrapolation
of current
situation
Extrapolation of current
situation
Conversion of manure
into biogas
Conversion of manure into
biogas
2018
2022
2042
1% conversion
20% conversion
40% conversion
5% conversion
30% conversion
60% conversion
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Driver Scenario A
baseline
Scenario B
low
Scenario C
intermediate
Scenario D
high
Wastewater No intervention
Slow implementation
Implementation as
planned
Accelerated implementation
2018
2022
2042
On-site: 50%
On-site: 50%
On-site: 50%
On-site: 50%
On-site: 66%, Central : 1%
On-site: 94%, Central : 6%
On-site: 50%
On-site: 85%, Central: 2%
On-site: 94%, Central: 6%
On-site: 50%
On-site: 69%, Central: 31%
On-site: 50%, Central: 50%
Tourists/
year
Business as
usual
Business as usual Best case Best case
2018
2022
2042
1,802,200
2,059,000
2,307,000
1,802,200
2,059,000
2,307,000
1,802,200
2,212,000
3,410,300
1,802,200
2,212,000
3,410,300
10.4.2 Reducing nutrient loads from aquaculture
While an integrated approach to water management is required for Lake Toba, water quality cannot be improved without reducing the current production of aquaculture. Four scenarios have been modelled to compare the impacts of low, intermediate and high levels of investments on the nutrient loading within Lake Toba. Interventions in aquaculture (Table 10.4) include: aiming for a gradual reduction of fish production under the intermediate scenario C and an accelerated, more rigorous approach under the high scenario D. In the modelling of nutrient outputs, these two options are compared to a baseline scenario (maintaining current production of 84,800 tons) and a growth scenario (B), in which production increases to 106,000 tons.
Table 10.4, Summary of targets and total estimated investment costs for the period 2018-2022 to reduce nutrient
loads from aquaculture into Lake Toba, in intermediate C and high D scenarios. C. Intermediate D. High
Target
production in 2022
FCR
50,000 tons
1.9
10,000 tons
1.2
Infrastructure 0 50
Institutional
Coordination 200 400
Law Enforcement 150 300
Training 2,400 12,000
Market Development 500 4,000
Information 6,450 17,400
Total (in million IDR) 9,700 34,150
US$ equivalent (000) 719 2,531
10.4.3 Managing livestock manure
The main source of pollution from livestock is manure. It can be used as organic fertilizer in
agriculture and as renewable energy source (biogas). The major recommendation for reducing
nutrient loads from livestock manure is to promote biogas production. Table 10.5 summarises
the targets and costs of biogas interventions for the period 2018 to 2022.
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Table 10.5, Summary of targets and total estimated investment costs for the period 2018-2022 to reduce nutrient
loads from livestock manure into Lake Toba, in intermediate C and high D scenarios.
C. Intermediate D. High CAPEX OPEX CAPEX OPEX
Target Conversion of manure into biogas (%)
20%
0%
Infrastructure 5,340 1,026 7,440 1,433
Institutional 2,800 4,400
information 3,750 5,500
Subtotal 5,340 7,576 7,440 11,333
Total (in million IDR) 12,916 18,773
US$ equivalent (000, split) 396 561 551 840
US$ equivalent (000, total) 957 1,391
10.4.4 Wastewater management
The major recommendation for reducing nutrient loads from domestic wastewater (including
from tourists) is to speed up the implementation of the current national sanitation strategies.
Funding has been reserved for these strategies, though this may only be sufficient for a
relatively slow implementation process, as included under the low scenario B. The more
ambitious targets for the intermediate C and high D scenarios are provided in Table 10.6,
together with the required investments between 2018 and 2022. Institutional and information
aspects are included in the operational costs that are given as total over 5 years.
Table 10.6, Summary of targets and total estimated investment costs for the period 2018-2022 to reduce nutrient
loads from domestic wastewater into Lake Toba, in low B, intermediate C and high D scenarios.
B. Low C. Intermediate D. High
CAPEX OPEX CAPEX OPEX CAPEX OPEX
Targets
Peak tourist numbers 343114 368623 368623
Access to
On-site and community-based
systems
Centralized systems
66%
1%
85%
2%
69%
31%
Infrastructure
On-site systems (individual septic
tanks, community-based systems
and IPLT)
636,000 89,180 1,154,000 116,531 370,000 93,566
Medium centralized 95,000 10,925 236,000 18,655 3,693,000 240,932
Subtotal 731,000 100,105 1,390,000 135,185 4,363,000 334,498
Reserved 730,472 100,105 730,472 100,105 730,472 100,105
Extra investment required (106 IDR) 528 0 659,528 35,081 3,632,528 234,393
Total (million IDR) 529 694,610 3,866,922
US$ equivalent (000, split) 39 0 48,872 2,600 269,176 17,369
US$ equivalent (000, total) 39 51,472 286,545
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10.4.5 Total investment costs for mitigating measures
As the graphs in chapter 8 showed, interventions in livestock and wastewater management have limited impacts on total nutrient loads in Lake Toba. An integrated approach with a rigorous reduction of aquaculture is required to significantly improve water quality in the lake. The total costs for each driver are summarized in Table 10.7 and
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Table 10.8, resulting in total investments for each scenario. Note that under scenario B, the only interventions are in domestic wastewater, while aquaculture production is allowed to grow in this scenario. Total rounded investment costs for the first five years (2018-2022) would be, in the low scenario B: IDR 529 million (US$ 39,000) for water quality management alone or IDR 103 billion (US$ 7.6 million) including monitoring. In the intermediate scenario C the costs would be IDR 717.2 billion (US$ 53.0 million) without, and IDR 958.1 billion (US$ 70.8 million) with monitoring. The five year costs of the high scenario D would be IDR 3,919.8 billion (US$ 290.5 million) for the most effective reduction in nutrients; combined with an aspirational water quality monitoring program the total costs would be IDR 4,381.4 billion (US$ 324.7 million).
Table 10.7, Summary of targets and total estimated costs for a low B, intermediate C and high D level of investment
to improve water quality in Lake Toba for the period 2018-2022 (in million IDR).
B. Low C. Intermediate D. High
CAPEX OPEX34 CAPEX OPEX CAPEX OPEX
Targets
Fish production 106,000 50,000 tons 10,000 tons
Conversion of manure into biogas 20% 30%
Peak tourist numbers 343,114 368,623 368,623
Access to
On-site and community-based
systems
Centralized systems
66%
1%
85%
2%
69%
31%
Investments
Aquaculture 9,700 34,150
Livestock 5,340 7,576 7,440 11,333
Wastewater35 528 0 659,528 35,081 3,632,528 234,393
Subtotal 528 0 664,868 52,357 3,639,968 279,876
Water quality management B. Low C. Intermediate D. High
Total (CAPEX + OPEX in million IDR)
for 5 years 529 717,225 3,919,845
Water quality monitoring
Total (million IDR) for 5 years 102,195 240,920 461,565
Total water quality management
and monitoring (million IDR) 102,724 958,145 4,381,410
34 Operational expenses for five years from 2018 to 2022. 35 For wastewater management, net required investments (minus reserved funds) are listed.
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Table 10.8, Summary of targets and total estimated costs for a low B, intermediate C and high D level of investment
to improve water quality in Lake Toba for the period 2018-2022 (in 000 US$ equivalents).
B. Low C. Intermediate D. High
CAPEX OPEX CAPEX OPEX CAPEX OPEX
Targets
Fish production 106,000 50,000 tons 10,000 tons
Conversion of manure into biogas 20% 30%
Peak tourist numbers 343,114 368,623 368,623
Access to
On-site and community-based
systems
Centralized systems
66%
1%
85%
2%
69%
31%
Investments
Aquaculture 719 2,531
Livestock 396 561 551 840
Wastewater36 39 0 48,872 2,600 269,176 17,369
Subtotal 39 0 49,268 3,714 269,727 20,739
Water quality management B. Low C. Intermediate D. High
Total (CAPEX + OPEX in 000US$) for
5 years 39 52,982 290,466
Water quality monitoring
Total (000 US$) for 5 years 7,573 17,853 34,203
Total water quality management
and monitoring (000 US$) 7,612 70,834 324,669
10.4.6 Mitigation options and effects on eutrophication
Changes in emissions have been modelled for the most contributing drivers aquaculture,
livestock and wastewater. The resulting nutrient concentrations in the lake have been
calculated based on a budget model approach. This approach does not take into account the
complexity of physical and biogeochemical processes, nor their variability in time and space.
Therefore, they do not account for long-term effects that could be aggravating (because of
accumulation effects) or improving (because of natural purification processes) the water quality
status of the lake. More detailed research is required to increase understanding of the long
term effects and processes affecting water quality in Lake Toba.
In the figures below the cumulative impact of the four combined scenarios on nutrient loads is presented, together with the resulting long-term concentrations for the whole lake and each of the four lake compartments. The scenarios are summarized in Table 10.3, while Figure 10.3 gives an overview of the four compartments. The displayed concentrations represent equilibrium concentrations on the basis of input data for 2018, 2022 and 2042. It may take tens of years to achieve each of these equilibrium states (Figure 7.13). Limits for oligotrophic and mesotrophic state have been indicated for nitrogen at 350 and 650 μg/l respectively, and for phosphorous at 10 and 30 μg/l (based on Nürnberg, 1996; Table C.2 in Annex C.3). Figure 8.12 shows the results for the whole lake and Figure 8.13 for the four compartments. The graphs show loads and long-term concentrations by compartment at fixed scales to enable comparisons between compartments.
36 For wastewater management, net required investments (minus reserved funds) are listed.
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Figure 10.3, Overview of the four compartments of Lake Toba in which the intervention scenarios have been
applied.
Figure 10.4, Projected impacts of four intervention scenarios (summarized inTable 10.3) on total loads and resulting
long-term concentrations of nitrogen (left) and phosphorous (right) for the whole of Lake Toba.
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Figure 10.5, Projected impacts of four intervention scenarios (summarized in Table 10.3) on total loads and
resulting long-term concentrations of nitrogen (left) and phosphorous (right) across four compartments
North, S1, S2, and S3 of Lake Toba (according to Figure 10.3).
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Without any interventions (scenarios A and B), nutrient concentrations will continue to rise,
leading to a long-term eutrophic state in the northern and southern compartment S1 for
phosphate and mesotrophic for nitrogen. The southern compartments S2 an S3 would remain
mesotrophic for phosphorous and oligotrophic for nitrogen. Substantial reductions in nutrient
loads, concentrations and trophic state can only be achieved in the two scenarios with reduction
of aquaculture: the intermediate C and high D scenarios.
For nitrogen (N), compartments S2 and S3 would remain oligotrophic in all scenarios. In the
northern compartment, increased loads under A and B would result in long-term concentrations
above the oligotrophic limit of 350 µg/l. This is mainly because of the loads from aquaculture
(Table 8.6 and Figure 8.5). In the smallest southern compartment S1, only scenario D would
lead to long-term concentrations below the limit for oligotrophic state, and scenario C in 2042,
with a maximum aquaculture production of 10,000 tons/year.
For phosphorous, the situation is different. For the lake as a whole, none of the scenarios would
eventually lead to an oligotrophic state. However, the effects differ significantly across the
compartments. In southern compartments S2 and S3, phosphorous loads from 2022 onwards
in scenario D would eventually bring the total phosphorous concentrations from a mesotrophic
level down to just below the oligotrophic limit of 10 µg/l. Concentrations in the northern
compartment N would slowly go down below the limit for a mesotrophic state, based on the
loads in 2022 and 2042 in scenarios C, and all years in scenario D.
Compartment S1 is the smallest and also the most problematic in terms of water quality.
Because of the intensive use with high population densities and livestock, the loads lead to very
high long-term concentrations. In scenario C and D aquaculture is halted completely, but loads
from livestock and wastewater each bring the long-term phosphorous concentration to levels
above the oligotrophic limit of 10 µg/l (Figure 8.7 and Figure 8.11). Combined, these loads lead
to a long-term mesotrophic state for phosphorous, even under scenarios C and D.
Only when mitigating measures in all sources: aquaculture, livestock and domestic loads are
applied, under the high scenario D, can the oligotrophic limit eventually be reached in
compartments S2 and S3. For the lake as a whole and in the northern compartment, the
mesotrophic limit will be feasible. For compartment S1 additional measures will be needed.
10.5 Investments for impact
While an integrated approach to water management is required for Lake Toba, water quality
cannot be improved without reducing the current production of aquaculture. Four scenarios
have been modelled to compare the impact of low, intermediate and high levels of investments
assumed to impact the nutrient loading within Lake Toba.
Only by reducing aquaculture in the lake to a total production level of 10,000 tons or less can
water quality in the lake be expected to improve, with long-term concentrations dropping below
the oligotrophic limit. This means that in the small compartment S1, no aquaculture is allowed
at all. Aquaculture can be reduced by further limiting licenses through coordination and
increasing law enforcement, supported by training in alternative livelihoods such as organic
farming and fisheries. The estimated total costs over five years would be IDR 9.7 billion (US$
719,000) under an intermediate scenario, gradually bringing down fish production, and IDR
34.2 billion (US$ 2.5 million) under a high investment scenario to reach the target of 10,000
tons of fish per year in 2022, limited to Haranggoal Bay and smallholders around the lake.
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Crucial to the success of these measures is the political commitment to not renew expired
licenses and implement more stringent regulations to ensure compliance.
Interventions in livestock manure and domestic wastewater management can reduce nutrient
loads to further strengthen the impact of measures in aquaculture. This is particularly important
in the northern compartment and in the smallest southern compartment S1. In these
compartments the long-term concentrations of phosphorous would reach levels above the
oligotrophic limit of 10 µg/l in N and the mesotrophic limit of 30 µg/l in S1, even without any
aquaculture.
The stimulation of conversion of livestock manure into biogas would require IDR 12.9 billion
(US$ 957,000) under an intermediate scenario, aiming for 20% conversion in 2022 and IDR
18.8 billion (US$ 1.4 million) under a high investment scenario resulting in 30% conversion. For
wastewater management, current national sanitation strategies could be accelerated,
accelerating the construction of individual and community-based on-site systems, based on
septic tanks. An intermediate scenario would provide 85% of the population in the catchment
area of Lake Toba with septic tank systems by 2022, for an extra investment of IDR 694.6 billion
(US$ 51.5 million), while a high investment scenario would provide access to centralized sewer-
based systems for 31% of the population for IDR 3,866.9 billion (US$ 286.5 million).
Investments in sanitation have a limited impact on nutrient reductions, but would make Lake
Toba more appealing to tourists.
For the smallest compartment S1, that is currently in a eutrophic state, urgent measures are
needed to reduce nutrient loads. Under the intermediate, high and alternative scenarios no
aquaculture is allowed in this compartment from 2042 in the intermediate scenario C and from
2022 in the high D and alternative E scenarios. The remaining drivers of eutrophication in this
compartment are nutrient loads from livestock and domestic wastewater. A dedicated survey
could identify the most important point and non-point sources of pollution around this
compartment, to target specific measures.
The targeted oligotrophic status can only be achieved through an integrated management plan
under a high investment scenario for three of the four compartments. Total net investment costs
for this scenario would be IDR 3,919.8 billion (US$ 290.5 million). The impacts of these
interventions on long-term nutrient concentrations would be different for each of the
compartments. In the southern compartments S2 and S3 the long-term phosphorous
concentrations would be around the oligotrophic limit of 10 µg per litre from 2022 onwards. In
the northern compartment, these concentrations would be just avove the limit. In the smallest
and most intensively used compartment (S1, west of Samosir), even high investments without
any aquaculture activities, would bring the long-term concentrations above the mesotrophic
limit of 30 µg per litre. The intermediate scenario, at a cost of IDR 717.2 billion (US$ 53.0
million) for the first five years, would get close to these results only in 2042. In 2022 the
intermediate scenario would not reach long-term oligotrophic concentrations for phosphorous
in any of the compartments.
A combination of options could be a cost-efficient approach, through selecting high investment
interventions for aquaculture and livestock, together with the intermediate interventions for
wastewater. This would be justified as the investments in sanitation have a relatively limited
impact on nutrients, even though it would make the area more appealing. The total costs over
five years of such an alternative combination (E, Table 10.9) would be IDR 747.5 billion (US$
55.4 million), a reduction of IDR 3.17 billion (US$ 235 million) as compared to the high scenario
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D, while the impacts on water quality would still be high because of the strong reduction in
aquaculture (Figure 10.6 and Figure 10.7).
Table 10.9, Summary of targets and total estimated costs for an alternative E level of investment to improve water
quality in Lake Toba for the period 2018-2022.
E. Alternative
(in million IDR)
E. Alternative
(in 000 US$)
CAPEX OPEX CAPEX OPEX
Targets
Fish production 10,000 tons
Conversion of manure into biogas 30%
Peak tourist numbers 368,623
Access to
On-site and community-based systems
Centralized systems
85%
2%
Investments
Aquaculture (high) 34,150 2,531
Livestock (high) 7,440 11,333 551 840
Wastewater37 (intermediate) 659,528 35,081 48,872 2,600
Subtotal 666,968 80,564 49,423 5,970
Water quality management
Total (CAPEX + OPEX) for 5 years 747,533 55,393
Water quality monitoring
(high, total for 5 years) 461,565 34,203
Subtotal water management and monitoring 666,968 542,129 49,423 40,173
Total
1,209,098
89,596
37 For wastewater management, net required investments (minus reserved funds) are listed.
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Figure 10.6, Nutrient loads of total nitrogen (left) and total phosphorous (right) resulting from a high D and
alternative E scenario to reduce nutrient emissions from aquaculture, livestock manure and wastewater, in
Lake Toba as a whole.
Figure 10.7, Projected impacts of three intervention scenarios (summarized in Table 8.14) on total loads and
resulting long-term concentrations of nitrogen (left) and phosphorous (right) in Lake Toba as a whole.
A comprehensive water quality monitoring program is required to determine long-term trends
in Lake Toba and inform an adaptive management approach. This should be based on
collaboration aligned with institutional responsibilities and free open source data sharing. When
combining the existing activities of the main water quality monitoring institutions, a
comprehensive approach can be achieved, encompassing signal, exploratory and statistical
functions. This should include regular sampling and analysing a range of variables for
background monitoring and depth profiles, at no less than forty stations distributed across the
lake. It is estimated to cost a minimum of IDR 102 billion (US$ 7.6 million) for a total of five
years, while an aspirational program building on latest technologies and involving stakeholders
is estimated to cost around IDR 462 billion (US$ 34.2 million).
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Sustained political commitment across all levels of government and sectoral coordination
among different stakeholders is essential to realising the government’s agenda for improving
the water quality and tourism value of Lake Toba. Such an approach needs to be supported by
a water quality and waste load monitoring program to continuously assess the impact of
interventions under the integrated management plan. This enables adaptive actions during
implementation. Together, the proposed interventions and monitoring plan would guide the
integrated management of water quality in Lake Toba and support the contribution of Lake
Toba to the economic and social development of Indonesia and serve as an example for the
management of other lake basins.
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Reservoir Management 12(4): 432–447. DOI 10.1080/07438149609354283
Oakley, J., 2015. Modelling the Aquaculture Carrying Capacity of Lake Toba, North Sumatra,
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Monitoring Program, Poster p. 8.
Ratman, D.R., 2016. Pembangunan Destinasi Pariwisata Prioritas 2016 – 2019. Available from
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Ross, K. A., Gashugi, E., Gafasi, A., Wüest, A., & Schmid, M., 2015. Characterisation of the
subaquatic groundwater discharge that maintains the permanent stratification within
Lake Kivu; East Africa. PloS One 10(3): e0121217. DOI 10.1371/journal.pone.0121217
RPJMN, 2014. Rencana Pembangunan Jangka Menengah Nasional (RPJMN) 2015-2019.
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Pembangunan Nasional (Ministry of National Development Planning / National
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Rustini, A.H., Lukman, and Iwan Ridwansyah, 2014. Estimation 2-dimensional flow pattern in
Lake Toba. Research Center for Limnology-LIPI. Limnotek 21 (1): 21-29
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Schmid, M., Tietze, K., & Halbwachs, M., 2003. How hazardous is the gas accumulation in
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A-6
A Stakeholder consultation process
A.1 Reference Group
Table A.1, Members of the Reference Group for the Water Quality Road Map for Lake Toba.
Institution/
Institusi
Name/
Nama
Position/
Posisi
Office/
Jabatan
Menko
Maritim
Dr. Rahman
Hidayat
Director/
Asisten Deputi
Department for Navigation, Fisheries
and Tourism Infrastructure/Departemen
Infrastruktur Pelayaran, Perikanan, dan
Pariwisata
PUPR-BPIW Hadi Sucahyono Head/ Kepala Center for Strategic Areas/Pusat
Pengembangan Kawasan Strategis
Menko
Maritim
Velly Asvaliantina,
M.Eng.Sc
Head/ Kepala Sector Nautical and Tourism
Infrastructure/Bidang Infrastruktur
Pariwisata Bahari
PUPR-BPIW Raymond Tirtoadi Repres/ Wakil Center for Strategic Areas/Pusat
Pengembangan Kawasan Strategis
LIPI Dr. Fauzan Ali Head/ Kepala Center of Limnology/Pusat Penelitian
Limnologi
LIPI Dr. Ir. Lukman
MSi.
Research/
Peneliti
Center of Limnology/Pusat Penelitian
Limnologi
BPPT Dr. Ir. Rudi
Nugroho, M.Eng.
Director/
Directur
Center for Environmental
Technology/Pusat Teknologi
Lingkungan
BPPT Prof. Dr. Titin
Handayani
Repres/ Wakil Center of Environmental
Technology/Pusat Teknologi
Lingkungan
KLHK Dr. Budi
Kurniawan
Repres/ Wakil Directorate for Water Pollution
Control/Direktorat Pengendalian
Pencemaran Air
KLHK Hermono Sigit Repres/ Wakil Directorate for Watershed and Aquatic
management/Direktorat Pengendalian
Kerusakan Perairan Darat
DLH-SU Dr. Ir. Hj. Hidayati Head/ Kepala Provincial Environment Agency North
Sumatra) /Badan Lingkungan Hidup
Sumatra Utara
BWS-S2 Baru Panjaitan Head/ Kepala Basin Management Center Sumatra II/
Balai Wilayah Sungai Sumatera II
BWS-S2 Novita R Section Head/
Kepala Seksi
Operation and Maintenance/Operasi &
Pemeliharaan
BOPDT Arie Prasetyo Head/ Kepala The Lake Toba Tourism Area
Management Authority/Badan Otorita
Pariwisata Danau Toba
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A.2 Meetings
A.2.1 Stakeholder meetings
Various group meetings have taken place during the project so far (Table A.2). Two NetMap
exercises were performed at the end of the two rounds of stakeholder meetings that took place
from 1 to 17 May and from 1 to 14 June. Minutes of meetings are grouped separately as
deliverable 6 (for internal use only).
Table A.2, Stakeholder meetings for WQ Roadmap in 2017.
Date Place Participants Topic
March 16 Jakarta Reference Group Kick off meeting
May 10 Jakarta Reference Group Inception
May 17 Jakarta Reference Group and
additional key
stakeholders
Presentation of initial stakeholder mapping
Discuss draft Legal, Institutional, and
Political Economy Assessment
First NetMap exercise
June 14 Laguboti,
North
Sumatra
Reference Group
Local level
participants
Second NetMap exercise
Presentation of initial findings Lake and
Catchment Assessment
August 7 Jakarta Reference Group Presentation and discussion of final Lake
& Catchment Assessment
August 24 Medan,
North
Sumatra
Reference Group
Local level
participants
Presentation of final Lake & Catchment
Assessment
Presentation of preliminary
recommendations
September
28
Jakarta Reference Group Draft recommendations
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A.2.2 Individual meetings
Various individual meetings and semi-structured interviews have been held as part of the
process of information collection for the WQ Roadmap.
Table A.3, Overview of meetings and interviews in 2017.
Name Institutions date team members
Bp. Fauzi BPDAS - Forestry 18-20 March JanJaap
Bp. Gunawan, Bp.
Giovandi Siahaan
PLTA Renun 22 March JanJaap, Henni,
Hanny, Satrio
Ibu Hidayati, Ibu Bayu
Nasution, Bp. Umanda
LH Province North
Sumatera
23 March Team
Ibu Made Sumiarsih Min. PUPR Central
Reservoirs (including lake)
25 April Bouke and Henni
Bp. Samsuhari, Ibu Inge Min. LHK 25 April Bouke and Henni
Bp. Mees Krimpen, Bp.
Amrizal, Bp. Dhanang
Wuryandoko, Bp. Arief
USDP 25 April Bouke and Henni
Bp. Wisnu, Bp. Ludfie ATR - BPN 18 May JanJaap and
Henni
Bp. Yosi Sukmono Bappeda North Sumatra 5 June Arina and Henni
Bp. Kusriadi replace by
Ibu Dolphin
Cipta Karya North
Sumatra
6 June Arina and Henni
Ibu Retno KKP (Perikanan) North
Sumatra
6 June Arina and Henni
Bp. Indra, Bp. Hendro LH Sampah North
Sumatra
6 June Arina and Henni
Bp. Bonar Tampubolon,
Bp. Dipman, Bp. Sirait,
Bp. Simanjuntak
PDAM Tirtonadi Waste
water treatment plant
division (field officer)
7 June Arina and Henni
Bp. Wisnu ATR - BPN 21 June JanJaap, Henni,
Nata
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B-1
B Detailed description of Lake Toba
B.1 Bathymetry
Lake Toba is formed in the caldera of the Toba Volcanic Complex. It is the largest volcanic lake
in the world. The deepest parts of the lake are approximately 500 meters deep (Table B.1).
Table B.1, Dimensions of Lake Toba (source QGIS/Open Streetmap).
Dimension Value
Perimeter 240 km
Longest diagonal 90 km
Longest width 30 km
Water surface area 1 124 000 000 m2
Lake water volume 256 200 000 000 m3
Mean depth 227 m
Maximum depth 505 m
Figure B.1 shows the lake area and the depth contour lines. Samosir Island is clearly visible in
the middle, more or less dividing the lake in two bigger parts to the north and south. In the
Southern part two relative shallower areas to the West and East can be identified and in the
middle a deep section can be seen. Originally, the island was a peninsula, but when a sluice
gate was constructed in the west and the narrow isthmus was cut, it became an island. The
strip of water to the west between Samosir and the main land is narrow and shallow; in the
model this became the southern compartment S1.
Figure B.1, Bathymetry of Lake Toba (Source: Lake Toba atlas, BWRMP-TOBA)
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B.2 Hydrological and administrative boundaries
The catchment area of Lake Toba and the Asahan River completely lies in the Province of
North Sumatra. There are several kabupaten that border the lake (Figure B.2):
• Samosir (Island and to the West), by far the largest land surface;
• Toba Samosir to the South East;
• Tupanuli and Humbang Hasundutan to the South West,
• Karo and Dairi to the North;
• Simalungun to the North East.
Figure B.2, Lake Toba Area (TBA) related districts/kabupaten: Dairi, Humbang Hasundutan, Karo, Pakpak Barat,
Samosir, Simalungun, Tapanuli Utara, and Toba Samosir.
In only two districts Lake Toba covers more than 25 percent of the kabupaten area (Samosir
(84%) and Toba Samosir 36%), while in the other kabupaten Lake Toba covers a far smaller
area. Pakpak Barat is part of the TBA, but does not drain into the lake. Therefore in calculations
of interventions only seven kabupaten are considered. Downstream from the water level
regulating dam at Siruar, the Asahan River flows through Kabupaten Asahan.
B.3 Soil
The soil in the region is typical for weathered volcanic areas. The geology of the Toba volcanic
lake has unique features (Chesner, 2012). The soils that have formed from the lava are
generally susceptible to erosion, which is important in the modelling of surface runoff.
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B-3
Within the catchment area four main soil types are found (Figure B.3). East of Lake Toba the
soil is a complex of lithosol and regosol that is highly sensitive to erosion, with podsilik brown,
sensitive to erosion, in the southeast. The west side of the lake mainly has the same brown
podzolic soils and on Samosir Island the majority of the soil is of the brown forest soil type that
is somewhat sensitive to erosion (Damage Control Directorate of Aquatic Ecosystems, 2017).
These are classified as follows:
- Light Clay (classification nr 2) - Clay Loam (classification nr 5) - Loam (classification nr 9) - Loamy Sand (classification nr 11)
These soil types in the hydrodynamic model determine the run-off rates and to estimate
groundwater flows. The data are very coarse, but sufficient for this rapid assessment.
Figure B.3, Soil types around Lake Toba.
B.4 Climate
The precipitation regime in the region is typical for the humid tropics and characterized by a
major wet season from August through to November and a minor wet season from March to
May. The months in between are transition-months with varying precipitation, never below 50
mm per month (Table B.2). The average yearly precipitation in the region during the period
2003-2016 amounts to approximately 2,850mm/year. However, within the short time series
significant differences in total precipitation from year to year can be seen (Figure B.4). In the
driest year (2005) total precipitation was only 2,198mm, while in the wettest year (2011) a total
of 3,489mm rain fell in the region. The period 2003-2016 (14 years) is too short to draw
conclusions on climatic trends.
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Table B.2, Monthly precipitation rates for the period 2003-2016 (source: Vernimmen, 2015)
Figure B.4, Total annual precipitation around Lake Toba from 2003 till 2016.
For this rapid assessment on the catchment hydrology with the purpose to draft a roadmap to
improve the water quality of Lake Toba, it suffices that the annual precipitation rate in the area
fluctuates significantly and there is a significant difference between the total amount of
precipitation in dry and wet years.
The temperature at Parapat, on the eastern shore of Lake Toba is stable, with an annual average of 21.5 degrees Celcius for the period 2006 to 2016 (Table B.3).
month 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 Average
1 137 130 57 113 145 133 108 179 189 102 278 117 213 92 142
2 189 191 81 106 69 89 149 160 178 273 280 114 90 136 150
3 375 270 212 149 170 271 355 201 281 178 129 122 191 80 213
4 325 267 190 293 334 331 312 255 330 422 279 295 259 176 291
5 247 143 144 268 268 179 195 149 260 237 250 212 260 226 217
6 255 124 108 151 149 167 137 212 144 114 125 147 129 184 153
7 215 388 188 132 212 224 230 321 159 234 146 70 131 181 202
8 146 187 190 194 215 307 367 276 586 334 311 493 346 176 295
9 434 487 206 227 286 296 350 372 310 319 294 209 221 239 304
10 423 389 349 248 402 427 497 233 514 315 422 331 136 255 353
11 341 347 243 212 345 214 263 446 352 393 341 266 338 339 317
12 191 210 230 176 146 167 198 245 186 244 329 301 173 282 220
Total 3278 3131 2198 2268 2740 2805 3160 3049 3489 3164 3183 2674 2484 2366 2856
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Table B.3, Monthly mean temperatures in Parapat for the period 2006-2016 (source: Meteorological, Climatological,
and Geophysical Agency (BMKG) , 2016)
Year
Month
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
2006 20,8 21,4 22,0 21,7 21,7 21,7 22,2 22,2 21,1 21,1 20,7 20,8
2007 21,1 21,0 21,3 21,6 22,1 21,7 21,7 21,3 21,6 20,7 21,3 20,6
2008 21,2 21,0 20,3 21,0 21,7 21,3 21,2 21,3 21,3 20,9 21,3 20,9
2009 20,4 21,0 21,2 21,9 22,6 22,3 22,1 21,9 21,8 21,7 21,2 21,1
2010 21,3 22,2 21,7 22,0 22,8 22,4 21,5 22,2 21,2 22,0 21,3 21,0
2011 20,5 20,7 21,2 21,7 22,0 22,2 22,4 21,4 21,7 21,3 21,3 21,0
2012 21,2 21,1 21,2 21,4 22,3 22,2 21,5 21,7 21,8 21,1 21,5 21,0
2013 21,4 20,6 22,1 22,3 22,3 22,3 22,1 22,2 21,6 21,8 21,0 21,2
2014 20,5 21,6 21,8 21,3 21,8 23,1 22,7 21,5 21,3 21,4 21,2 20,8
2015 20,9 21,0 21,4 21,3 21,5 21,3 21,8 21,2 21,5 21,2 21,0 21,3
2016 21,8 21,4 22,6 22,5 22,3 22,1 21,8 22,7 22,4 22,7 21,5 21,5
Average
21,0 21,2 21,5 21,7 22,1 22,1 21,9 21,8 21,6 21,4 21,2 21,0
Potential reference evaporation was based on the global 1 x 1 km CGIAR-PET monthly data
set (available from: http://www.cgiar-csi.org; Zomer et al., 2008). The data is based on the
Hargreaves model. This model performed almost as well as the Penman-Monteith model, but
required less parameterization, with significantly reduced sensitivity to error in climatic inputs
(Hargreaves and Allen, 2003). Average annual reference evaporation for the Toba-Asahan river
basin was computed at 1,556 mm.
B.5 Water level
The objective of the regulating dam is to manage Toba outflow to the Asahan River in such a
way that the Toba Lake water levels are within the range required for various uses on site and
downstream. Hence the Asahan flow needs to meet downstream requirements, i.e. sufficient
for electric power generation and other downstream uses, and must at the same time avoid
flood damage along downstream sections of the Asahan River.
The water level of Lake Toba can be operated through variation of the outflow through the
regulating gate at Siruar. In principle, the water level is kept between 905.25m and 902.50m
above sea level. This is done with a release that varies between 90 and 140m3/s to the
downstream Asahan River (Figure B.4).
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Figure B.5, Monthly averaged discharges at the Siruar Regulating Dam, the Siguragura Dam and the Tangga Dam
(expressed in m3/s) for the period 1957 to the present (source: PT Inalum)
Figure B.5 shows the end-of-month Toba Lake water level (in meters above mean sea level /
MSL) from the year 1975 to the present (source: PT Inalum). The figure illustrates that given
runoff from the surrounding slopes and Samosir Island, the inflow from PLTA Renun (since
1993), water consumption around Toba Lake, and precipitation on and evaporation from the
lake, the Siruar Dam is operated since the early 1980’s in such a way that Lake Toba water
levels do not exceed the maximum water level and does not fall below the minimum desired
water level. This is done in order not to interrupt the intensive use the Toba Lake shoreline for
fishing, boating, aquaculture, and recreational activities, and to not cause damage to the related
infrastructure like port facilities or shore protection. Only during May, June and July 1998, the
level dropped below the minimum water level (to a minimum of 902.28m above sea level), and
consequently, the discharge via the Siruar Regulating Dam was reduced. If the water level
comes close to the maximum level of 905.5m more water is released, to keep the level from
rising too high. Above this level certain settlements are flooded. The extra water is released
through the spillways of the structures in the cascade, and cannot be used for hydropower
generation.
0.0
50.0
100.0
150.0
200.0
250.0
300.0
350.0
Jan-55 Jan-60 Jan-65 Jan-70 Jan-75 Jan-80 Jan-85 Jan-90 Jan-95 Jan-00 Jan-05 Jan-10 Jan-15
Monthy averaged discharge Siruar Regulating Dam (m3/s)
Monthly averaged Siguragura discharge turbines + spillway (m3/s)
Monthly averaged Tangga discharge turbines + spillway (m3/s)
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Figure B.6, End of month Toba Lake water level (in meters above mean sea level / MSL) from 1975-2015 (source:
PT Inalum).
902.0
902.5
903.0
903.5
904.0
904.5
905.0
905.5
906.0
Jan-55 Jan-60 Jan-65 Jan-70 Jan-75 Jan-80 Jan-85 Jan-90 Jan-95 Jan-00 Jan-05 Jan-10 Jan-15
End of month Lake Toba water level (m+MSL)
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C-1
C Background on functioning of lakes
C.1 Theory of residence time
A consequence of the large water body and the relative small outflow is the long residence time
of the water in Lake Toba. The concept of water residence time (or turnover time) is particularly
important. The residence time of lakes may range from a few days to many tens of years, or
even to a century or more. A simple form of residence time can be calculated by dividing the
lake volume by the outflow (Chapman, 1996). Lake Toba’s theoretical residence time is
approximately 80 years:
(256,200,000,000𝑚3) (100 𝑚3 𝑠⁄ × (60 × 60 × 24 × 365)) = 81.2 𝑦𝑟⁄
The residence time as calculated above is however purely theoretical, because it is based on
the assumption of homogeneous mixing of the lake. Stratified lakes (such as Lake Toba) have
a much longer residence time than the theoretical value (Meybeck, 1995).
Why is the concept of residence time important? The potential recovery time of a lake through
replacement of polluted lake water by clean inflowing water, depends on it. If Lake Toba
becomes polluted with a soluble toxic element, and the source of the pollution is eliminated, it
will take much more than 80 years to remove the polluted water and replace it with non-polluted
water. However, since the residence time in deeper layers may be longer, 80 years’ recovery
time is likely an optimistic estimate. The lake recovery may only be faster if natural water quality
processes within the lake itself are able to decompose the water pollution. Figure C.1 shows
the relation between the scale of water bodies, the recovery time and the reversibility of the
lake system’s state. Lake Toba borders on the category of ‘Irreversible’.
Figure C.1, Schematic representation of the scale of water bodies, recovery time and reversibility of water quality
issues. (Source: Chapman, 1996)
C.2 Theory of biochemical processes
A simplified view of the biogeochemical processes in lakes is shown in Figure C.2. Nutrients
enter the system via river discharges and run-off, or from aquaculture. There they may be taken
up by algae. Algae produce oxygen through photosynthesis, while they consume oxygen
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C-2
through respiration. This results in a daily oxygen variation, with oxygen concentrations
increasing during daytime and decreasing during night time. When the algae die, they change
into detritus, which settles into the deeper lake layers. The detritus may accumulate in the
hypolymnion or at the bottom. There, it could be mineralized back into inorganic nutrients. Since
the mineralization process consumes oxygen, this decreases the oxygen concentrations in the
deeper layer of the lake. Also, fermentation processes may lead to the local accumulation of
methane or carbon dioxide.
Figure C.2, A simplified overview of biogeochemical processes in a lake.
In deep lakes, such as Lake Toba, algal growth is typically limited by light. This is because of
the large epilimnion depth over which the algae are being mixed. During their travels over the
epilimnion they experience light conditions that are on average too small to result in a positive
production flux. Occasionally, however, the depth over which the algae are being mixed is
decreased, due to a change of the (primary or secondary) thermocline depth. Once the light
limitation is removed, an algal bloom may occur. Therefore, the thermocline depth is a key
factor determining the occurrence of algal blooms. Also, thermocline depth determines the
volume over which the nutrients are diluted. Because of its (twofold) importance, thermocline
depth is a key factor.
The peak biomass concentration of the algal bloom is determined by the availability of nutrients.
Nutrient addition from run-off (land activities) and direct input from aquaculture, can lead to
higher nutrient concentrations in the upper layer above the thermocline. This may thus lead to
higher algal biomass in the event of an algal bloom.
Nutrient addition in the form of organic waste however may sink to the hypolimnion, where it is
mineralized, thus leading to higher nutrient concentrations and lower oxygen concentrations
mainly in the deep layers of the lake. Once arrived in the deeper layers, these nutrients will not
directly affect the epilimnion anymore. Since the volume of the hypolimnion is so large, the
increase in nutrient concentration may increase very slowly, at a pace that only becomes visible
when assessed over large periods of time.
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C-3
Although the nutrient loading of the hypolimnion does not affect the epilimnion directly, it does
entail some risks. During mixing events, for example, nutrients from the hypolimnion may be
returned to the epilimnion. This may support larger algal biomass peaks. Also, when the
hypolimnion is anoxic, the oxygen concentrations in the epilimnion may drop substantially
during a mixing event. This may have large impact on all biology in the epilimnion, and in some
cases even lead to mass mortality events. Even worse may be events of mixing during which
large amounts of CO2 are brought up, which in Lake Nyos suffocated 1,746 people and 3,500
livestock in nearby towns and villages (Giggenbach, 1990).
C.3 Trophic level classification
A qualitative classification based on trophic level is shown in Table C.1 (Chapman, 1996;
Nürnberg, 1996). These classes are basically a continuous range of nutrient concentrations
and associated biomass production (Carslson, 1977).
Table C.1, Lake classification based on trophic level (Chapman, 1996; Nürnberg, 1996)
Classification Description
Oligotrophic
lakes
Lakes of low primary productivity and low biomass associated with low
concentrations of nutrients (N and P). In temperate regions the fish fauna is
dominated by species such as lake trout and whitefish. These lakes tend to
be saturated with O2 throughout the water column.
Mesotrophic
lakes
These lakes are less well defined than either oligotrophic or eutrophic lakes
and are generally thought to be lakes in transition between the two
conditions. In temperate regions the dominant fish may be whitefish and
perch.
Eutrophic lakes Lakes which display high concentrations of nutrients and an associated high
biomass production, usually with a low transparency. In temperate regions,
the fish communities are dominated by perch, roach and bream. Such lakes
may also display many of the effects which begin to impair water use.
Oxygen concentrations can get very low, often less than 1 mg/l in the
hypolimnion during stratification.
Hypereutrophic
lakes
Lakes at the extreme end of the eutrophic range with exceedingly high
nutrient concentrations and associated biomass production. In temperate
regions the fish communities are dominated by roach and bream. The use of
the water is severely impaired as is described below. Anoxia or complete
loss of oxygen often occurs in the hypolimnion during stratification.
Dystrophic
lakes
These are organic rich lakes (humic and fulvic acids) with organic materials
derived by external inputs from the watershed.
The quantitative boundaries of nutrient and chlorophyll concentrations with which to define the
trophic levels vary a bit between scientists and organizsations (Table C.2). Some classifications
are based on more variables, including for example Secchi depth and oxygen (Table C.3). BLH-
SU uses the KLH (2009) boundaries. Most boundaries are similar, although the KLH nitrogen
boundaries are relatively high, with the oligotrophic-mesotrophic boundary of 650 µg total N per
litre being almost twice the value of the other boundaries. This may provide a reason to use the
other boundaries instead. However, changing to different boundaries should be supported by
all stakeholders. Additionally, Chapman (1996) provides nutrient levels including Secchi disk
values. Also, he differentiates between mean annual values for chlorophyll an absolute
maximum and Secchi disk an absolute minimum (Table C.3).
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Table C.2, List of total P, N and Chl-a concentrations (µg/l) for different trophic states. In this report the cut-off
values proposed by Nürnberg (1996, highlighted in yellow) have been applied.
Variable Oligotrophic-
mesotrophic
Mesotrophic-
eutrophic
Eutrophic-
hypereutrophic
Reference
P 10 30 100 Nürnberg (1996)
15 25 100 Forsberg and Ryding (1980)
10 25 100 Jones and Knowlton (1993)
10 30 100 KLH (2009)
N 350 650 1,200 Nürnberg (1996)
400 600 1,500 Forsberg and Ryding (1980)
300 500 1,200 Jones and Knowlton (1993)
650 750 1,900 KLH (2009)
Chl a 3.5 9 25 Nürnberg (1996)
3 7 40 Forsberg and Ryding (1980)
3 7 40 Jones and Knowlton (1993)
2 5 15 (hyp. > 200) KLH (2009)
Table C.3, Nutrient levels, biomass and productivity of lakes for trophic classes (Chapman, 1996).
Trophic
category
Mean total
phosphorou
s (mg m-3)
Annual
mean
chlorophyl
l (mg m-3)
Chlorophyl
l maxima
(mg m-3)
Annual
mean Secchi
disc
transparenc
y (m)
Secci disc
transparenc
y minima
(m)
Minimu
m
oxygen
(%sat)1
Ultra-
oligotrophic
4 1 2.5 12.0 6.0 <90
Oligotrophic 10 2.5 8 6.0 3.0 <80
Mesotrophic 10-35 2.5-8 8-25 6.0-3.0 3.0-1.5 40-89
Eutrophic 35-100 8-25 25-75 3.0-1.5 1.5-0.7 40-0
Hypereutrophi
c
100 25 75 1.5 0.7 10-0
1 The percentage saturation in bottom waters depending on mean depth.
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D-1
D Background on DPSIR
The Driver, Pressure, State, Impact, Response (DPSIR) concept is developed to help systematic analysis of complex issues and to streamline insight and appropriate responses within large groups of stakeholders. It is a flexible scheme assists decision-makers in many steps of the decision process (Figure D.1). DPSIR was initially developed by the Organisation for Economic Co-operation and Development (OECD) and is in use by the US-EPA, United Nations (UNEP), and European Environmental Agency (EEA). This scheme relates human activities to the state of the environment, identifies (often negative) impacts and formulates responses. Table D.1 lists the definitions that describe the elements in DPSIR38.
Figure D.1, Driver, Pressure, State, Impact, Response (DPSIR).
Table D.1, Descriptions for Driver, Pressure, State, Impact and Response (source: EPA)
Element Description
Driver Drivers are the social, demographic and economic developments in societies and
the corresponding changes in life styles, overall levels of consumption and
production patterns. In particular, Drivers are often defined as socio-economic
sectors that fulfil human needs for
• food,
• water,
• shelter,
• health,
• security,
• and culture.
Driving forces can originate and act globally, regionally or locally.
38 For more information about systems thinking and the DPSIR concept, see
https://archive.epa.gov/ged/tutorial/web/html/index.html.
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Element Description
Pressure Drivers function through human activities which may intentionally or
unintentionally exert Pressures on the environment. Human activities that exert
pressure include:
• Land use changes
• Resource consumption
• Release of substances
• Physical damage through direct contact
Pressures depend on the kind and level of technology involved in source
activities, and can vary across geographic regions and spatial scales.
State The pressures exerted by society may lead to unintentional or intentional
changes in the State of the ecosystem. Usually these changes are unwanted and
are seen as negative (damage, degradation). The pressures exerted by society
may directly impact the ecosystem, such as harvesting or dredging, or may be
transported and transformed through a variety of natural processes to indirectly
cause changes in ecosystem conditions.
The State is the condition of the abiotic and biotic components of the ecosystems
in a certain area in terms of:
• Physical variables - the quantity and quality of physical phenomena such
as temperature or light availability
• Chemical variables – the quantity and quality of chemicals such as
atmospheric CO2 concentrations or nitrogen levels
• Biological variables – the condition at the ecosystem, habitat, species,
community, or genetic levels, such as fish stocks or biodiversity
Impact Changes in the quality and functioning of the ecosystem have an Impact on the
welfare or well-being of humans through the provision of ecosystem services.
Ecosystem goods and services are ecosystem functions or processes that
directly or indirectly benefit human social or economic drivers, or have the
potential to do so in the future.
Ecosystem processes benefit humans through
• Provisioning of food, timber, water
• Regulation of air quality, water quality, or disease
• Cultural benefits including aesthetic or recreational value
• Indirect supporting processes that maintain the ecosystem
The value of ecosystem services depends on human need and use (e.g., market
value).
Response Humans make decisions in Response to the impacts on ecosystem services or
their perceived value. Responses are actions taken by groups or individuals in
society and government to prevent, compensate, ameliorate or adapt to changes
in the state of the environment by seeking to:
• Control drivers or pressures through regulation, prevention, or mitigation
• Directly maintain or restore the state of the environment
• Deliberately “do nothing”
Decision making processes occur at a variety of scales, from individuals to local
management to federal government.
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E-1
E Institutional assessment
For the institutional or political economy assessment to be useful for practitioners, the World
Bank approach (Fritz et al., 2014) has been applied. This consists of the following steps:
1. Start with a diagnosis of the specific problem and identify dysfunctional patterns;
2. Analyse why the observed patterns are present, covering three dimensions:
a) Relevant structural factors that influence stakeholder positions
b) Existing institutions, including institutional dysfunctions that channel behaviour
c) Stakeholder interests and constellations
3. Identify ways forward.
The stakeholder assessment/mapping and legal, institutional and political economy
assessment are interlinked, as presented in the three key types of factors that are commonly
considered in governance and political economy analysis (Figure E.1).
Figure E.1, Three clusters of drivers (Fritz et al. 2009).
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F-1
F Overview of relevant legislation
F.1 List of laws in English
Acts 1. Act No. 5 of 1990 on the Conservation of Biological Natural Resources and its
Ecosystem
2. Act No. 41 of 1999 on Forestry
3. Act No. 26 of 2007 on Spatial Planning
4. Act No. 32 of 2009 on Environmental Protection and Management
5. Act No. 23 of 2014 on Regional Government
Government Regulation 6. Government Regulation No. 82 of 2001 on Water Quality Management and Water
Pollution Control
7. Government Regulation No. 44 of 2004 on Forest Planning.
8. Government Regulation No. 45 of 2004 on Forest Protection
9. Government Regulation No. 26 of 2008 on National Spatial Planning.
10. Government Regulation No. 42 of 2008 on Forest Planning.
Presidential Regulation 11. Presidential Regulation No. 81 of 2014 on spatial planning of Lake Toba and its
surrounding
12. Presidential Regulation No. 49 of 2016 on the Management Authority of Lake Toba
Tourism Area
Presidential Decree 13. Presidential Decree No. 32 of 1990 on Protected Areas Management
14. Presidential Decree No. 2 of 2014 on the addition of Jasa Tirta 1 Company’s working
area in Toba Asahan river, Serayu Bogowonto River and Jrantunseluna river.
Ministerial Regulation 15. Ministry of Health Regulation No. 416/1990 on the requirements of Water Quality
Supervision.
16. Ministry of Health Regulation No. 907 of 2002 on the Requirements and Supervision of
Drinking Water Quality.
17. Ministry of Environment Regulation No. 111 of 2003 on the Guidance of Requirements
and Licensing Procedures along with the Guidance on Waste Disposal to Water and
Water Sources.
18. Ministry of Environment Regulation No. 28 of 2009 on the capacity of pollution load on
Lake and Reservoir Water.
19. Ministry of Public Work and Public Housing Regulation No. 4 of 2015 on River Area
Criteria and Stipulation
20. Ministry of Public Work and Public Housing Regulation No. 9 of 2015 on Water
Resources Utilization.
21. Ministry of Public Work and Public Housing Regulation No. 10 of 2015 on Planning and
Technical Planning of Water Governance and Irrigation system.
22. Ministry of Public Work and Public Housing Regulation No. 28 of 2015 on the stipulation
of River border line and Lake border line
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23. Ministry of Public Work and Public Housing Regulation No. 37 of 2015 on the license
of Water and/or Water sources use.
24. Ministry of Environment and Forest Regulation No. 68 of 2016 on Water Waste Quality
Standard.
25. Ministry of Public Work and Public Housing Regulation No. 4 of 2017 on the
implementation of Domestic Water Waste Management system.
North Sumatra Governor Regulation 26. North Sumatra Governor Regulation No. 30 of 2008 on the Management Coordination
Board of Lake Toba ecosystem area.
27. North Sumatra Governor Regulation No. 1 of 2009 on the water quality standard of
Lake Toba in North Sumatra Province.
28. North Sumatra Governor Regulation No. 18 of 2009 on the Preservation Coordination
Board of Lake Toba ecosystem area.
North Sumatra Governor Decree 29. North Sumatra Governor Decree No. 062.05/255/K/2002 on the Preservation
Coordination Board of Lake Toba ecosystem area.
30. North Sumatra Governor Decree No. 614/468 of 2008 on the formation of Asahan -
Toba watershed Management Forum
31. North Sumatra Governor Decree No 188.44/209/KPTS/2017 on Lake Toba trophic
status
32. North Sumatra Governor Decree No. 188.44/213/KPTS/2017 on the Capacity of Lake
Toba pollution load and carrying capacity for Fisheries cultivation.
Regional Regulation No. 7 of 2003 on North Sumatra Spatial Planning is currently (July 2017)
being updated and still in the process of legalization in the Governor’s office.
F.2 List of laws in Bahasa Indonesia
Undang-Undang
1 Undang-Undang Nomor 5 Tahun 1990 tentang Konservasi Sumber Daya Alam Hayati
dan Ekosistemnya;
2 Undang-Undang Nomor 41 Tahun 1999 tentang Kehutanan;
3 Undang-Undang Nomor 32 Tahun 2004 tentang Pemerintahan Daerah;
4 Undang-Undang Nomor 26 Tahun 2007 tentang Penataan Ruang;
5 Undang-Undang Nomor 32 Tahun 2009 tentang Perlindungan dan Pengelolaan
Lingkungan Hidup.
Peraturan Pemerintah
6 Peraturan Pemerintah Nomor 82 Tahun 2001 tentang Pengelolaan Kualitas Air dan
Pengendalian Pencemaran Air;
7 Peraturan Pemerintah Nomor 44 Tahun 2004 tentang Perencanaan Kehutanan;
8 Peraturan Pemerintah Nomor 45 Tahun 2004 tentang Perlindungan Hutan;
9 Peraturan Pemerintah No. 26 Tahun 2008 tentang Rencana Tata Ruang Wilayah
Nasional;
10 Peraturan Pemerintah No. 42 Tahun 2008 tentang Perencanaan Kehutanan;
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F-3
Peraturan Presiden
11 Perpres No. 81/2014 – Peraturan Presiden No. 81 Tahun 2014 tentang Rencana Tata
Ruang Kawasan Danau Toba dan sekitarnya
12 Perpres No. 49/2016 – Peraturan Presiden No. 49 Tahun 2016 tentang Badan Otorita
Pengelola Kawasan Pariwisata Danau Toba
Keputusan Presiden
13 Keputusan Presiden Nomor 32 Tahun 1990 tentang Pengelolaan KawasanLindung;
14 Keppres No. 2/2014 – Keputusan Presiden Nomor 2 Tahun 2014 tentang Penambahan
Wilayah Kerja Perusahaan Umum (PERUM) JASA TIRTA I di Wilayah Sungai Toba
Asahan, Wilayah Sungai Serayu Bogowonto, dan Wilayah Sungai Jratunseluna
Peraturan Menteri
15 Peraturan Menteri Kesehatan Nomor 416/1990 tentang Syarat- Syarat Pengawasan
Kualitas Air;
16 Keputusan Menteri Kesehatan Nomor 907 Tahun 2002 tentang Syarat dan Pengawasan
Kualitas Air Minum;
17 Keputusan Menteri Negara Lingkungan Hidup Nomor 111 Tahun 2003 tentang Pedoman
mengenai Syarat dan Tata Cara Perijinan serta Pedoman Pembuangan Limbah ke Air
dan Sumber Air.
18 Peraturan Menteri Negara Lingkungan Hidup Nomor 28 Tahun 2009 tentang Daya
Tampung Beban Pencemaran Air danau dan/atau Waduk;
19 Peraturan Menteri PUPR Nomor 4 tahun 2015 tentang Kriteria dan Penetapan Wilayah
Sungai
20 Peraturan Menteri PUPR Nomor 9 tahun 2015 tentang Penggunaan Sumber Daya Air
21 Peraturan Menteri PUPR Nomor 10 tahun 2015 tentang Rencana dan Rencana Teknis
Tata Pengaturan Air dan Tata Pengairan
22 Peraturan Menteri PUPR Nomor 28 tahun 2015 tentang Penetapan Garis Sempadan
Sungai dan Garis Sempadan Danau
23 Peraturan Menteri PUPR Nomor 37 tahun 2015 tentang Izin Penggunaan Air dan/atau
Sumber Air
24 Peraturan Menteri Lingkungan Hidup Kehutanan Nomor 68 Tahun 2016 tentang Baku
Mutu Air Limbah
25 Peraturan Menteri PUPR Nomor 4 Tahun 2017 tentang Penyelenggaraan Sistem
Pengelolaan Air Limbah Domestik
Peraturan Gubernur Sumatera Utara
26 Peraturan Gubernur Sumatera Utara No. 30 tahun 2008 tentang Badan Koordinasi
Pengelolaan Ekosistem Kawasan Danau Toba
27 Peraturan Gubernur Sumatera Utara Nomor 1 Tahun 2009 tentang Baku Mutu Air Danau
Toba di Provinsi Sumatera Utara;
28 Peraturan Gubernur Sumatera Utara Nomor 18 Tahun 2009 tentang Badan Koordinasi
Pelestarian Ekosistem Kawasan Danau Toba.
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Keputusan Gubernur Sumatera Utara
29 Surat Keputusan Gubernur Sumatera Utara Nomor 062.05/255/K/2002 tentang Badan
Koordinasi Pelestarian Ekosistem Kawasan Danau Toba.
30 Surat Keputusan Gubernur Sumatera Utara No. 614/468 tahun 2008 tentang
Pembentukan Forum Pengelolaan Daerah Aliran Sungai Asahan – Toba
31 Surat Keputusan Gubernur Sumatera Utara Nomor 188.44/209/KPTS/2017 tentang
Status Trofik Danau Toba
32 Surat Keputusan Gubernur Sumatera Utara Nomor 188.44/213/KPTS/2017 tentang Daya
Tampung Beban Pencemaran dan Daya Dukung Danau Toba untuk Budidaya Perikanan
Peraturan Daerah Nomor 7 Tahun 2003 tentang Rencana Tata Ruang Wilayah Provinsi
Sumatera Utara is currently (July 2017) being updated and still in the process of legalization in
the Governor’s office.
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G-1
G Water quality data PJT1
Perusahaan Umum Jasa Tirta, or Perum Jasa Tirta 1 (PJT1) is the national corporation for
basin management, responsible for Toba Asahan and other river basins. PJT 1 has recently
started monitoring water quality at 20 sites in the Toba Asahan basin (Figure 3.4), together with
the Sepuluh Nopember Institute of Technology, Surabaya. The water quality data from these
sampling locations were not available at the time of the modelling yet, but have been included
here for comparison. Table G.1 shows the values of several parameters measured at the
sampling stations displayed in Figure 3.4.
Table G.1, Results of water quality (in mg/l) at 8 points by PJT1 in 2016 and 2017.
Para
mete
r
Wate
r q
ua
lity
sta
nd
ard
Location
date
Refe
ren
ce
po
int
Bakkara
Nain
gg
ola
n
Hil
ir D
an
au
Sim
alu
ng
un
Sip
iso
-pis
o
Dair
i
To
mo
k
DO
May ‘16 4 6.6 6.6 - 4.8 5.4 5.2 4.3 4.7
Sep ‘16 4 - - - 7.5 6.6 6.4 6.5 5.6
Jan ‘17 4 5.6 5.6 5.5 5.0 5.5 4.8 5.1 5.2
Apr ‘17 4 5.6 5.2 5.4 5.3 5.4 5.1 4.9 5.1
Jul ‘17 4 4.9 4.2 4.0 4.0 4.8 4.2 4.0 4.0
BO
D
Mei ‘16 3 5.1 3.9 - 3.8 9.2 4.9 9.4 9.0
Sep ‘16 3 - - - 3.2 3.1 3.2 3.4 3.2
Jan ‘17 3 6.5 5.5 13.6 6.3 4.7 4.3 4.9 12.0
Apr ‘17 3 3.89 6.91 2.54 3.20 3.59 4.75 2.01 3.54
Jul ‘17 3 5.55 4.55 4.80 6.35 6.30 7.35 4.45 4.75
CO
D
Mei ‘16 25 17.28 7.70 - 7.04 21.23 13.10 22.30 20.27
Sep ‘16 25 - - - 7.15 9.32 8.62 8.95 8.51
Jan ‘17 25 23.08 23.56 38.91 21.17 14.12 12.34 14.80 37.62
Apr ‘17 25 14.37 29.63 8.30 13.02 12.67 12.94 7.56 14.66
Jul ‘17 25 18.22 17.32 15.37 16.31 17.40 16.39 12.92 14.48
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H-1
H Methodology of stakeholder assessment
H.1 Theoretical framework
H.1.1 Stakeholder roles and functions
In accordance with the Indonesian water law39 as laid out in the Strategic Plan (Pola) and River
Basin Plan (Rencana), five important stakeholder roles can be identified (Figure H.1):
Figure H.1, Stakeholder roles as identified in the 2013-2015 TKPSDA process.
1. Regulator – the government, creating an enabling environment for efficient and effective
water resource management (WRM). This is called the “regulator” function because the
main instruments employed are laws and regulations to guide the activities of other parties
involved in WRM including management and monitoring of water quality.
2. Coordinator – the stakeholder that must achieve a balance between the other functional
categories to ensure sustainable utilization and preservation of resources as well water
safety (protection from the destructive power of water). Coordination also involves non-
water organizations whose activities have a direct or indirect impact on water resources,
such as Kementerian Lingkungan Hidup dan Kehutanan (KLHK, the Ministry of
Environment and Forestry) for conservation and pollution control; Kementerian Energi dan
Sumber Daya Mineral (ESDM, the Ministry of Energy and Mineral Resources) for licensing
of groundwater abstraction; and Badan Pertanahan Nasional-Kementerian Agraria dan
Tata Ruang/ (BPN-ATR, the National Land Agency at the Agrarian and Spatial Planning
Ministry) for flood management through spatial planning and land-based infrastructure.
3. Operator – institutions in charge of the daily operation of infrastructure assets to manage
and monitor water resources, including water quality. In most basins, the operator function
is carried out at provincial and district-level government level.
39 Water Resources Law 7/2004 and Regulation 4/2008 have expired in 2015. The new law and regulation are still in the
process of being formally approved by parliament. For this section, the concept text has been used.
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4. Developer – any party involved in the development of physical infrastructure that offers
protection from or enables the utilization of water, or protects water as a resource in terms
of quantity and quality. Examples include dams, levees, irrigation canals, water supply or
sewage treatment facilities, aqueducts, and sewers. Generally, this function is carried out
by (semi-) government or publicly-owned organizations such as Pengelolaan Sumber Daya
Air (PSDA, water resources management), Perusahaan Daerah Air Minum (PDAM, the
regional water supply company), and Perusahaan Umum Jasa Tirta (PJT, national
corporation for basin management).
5. User – large-scale users of water as well as individual users, e.g., individual farmers. Large-
scale users may in turn represent individual consumers. Relevant examples are water
supply companies, irrigation systems, and hydropower plants. The users comprise not only
government or state-owned enterprises but also private organizations such as breweries,
bottlers, and paper mills.
This stakeholder concept proved very effective in the stakeholder processes of Kementerian
Pekerjaan Umum Dan Perumahan Rakyat, (PUPR, the Ministry of Public Works and Housing)
and has been widely accepted in Indonesia. The concept is especially strong when combined
with the “expected/appointed role/responsibility” of the different stakeholders in the process -
in this case, the relation/role/responsibility for the WQ roadmap for Lake Toba. Interestingly, in
the Indonesian water law, no strict distinction is made between water quality monitoring and
water quality management. In the roles of regulator and operator water quality management
and monitoring are mentioned together as two aspects of one responsibility.
For each key point and non-point source of pollutants, however, the key stakeholders and the
legal, institutional and PE context are different. The legal and institutional setting may be similar
for each of the water quality interventions as it does not depend much on the different sets of
treatment measures. For implementation and maintenance of most of the WQ measures, the
lower level administrative Kecamatan (sub-district) level is crucial, and thus it is important to
determine the role of these local administrations. A total of 46 Kecamatan are included in the
assessment (Figure H.2).
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H-3
Figure H.2, Lake Toba Area related sub-districts (kecamatan).
H.1.2 Social network analysis
Social network analysis defines and analyses the relationships that organizations or individuals
have with each other by focusing on the positions and structural patterns of the actors. It can
highlight which stakeholders are important for influencing policy, initiating actions or facilitating
information and knowledge transfer. The analysed network perspectives can improve the
effectiveness of a network (intra-organizational or inter-organizational) by identifying points of
misalignment and accelerating collaboration in the right places. It can also help determine
whether certain organizations and functions are achieving the connectivity required for desired
results and identify and track intervention strategies if they are not. Network analysis can also
highlight top performers in a network and determine reasons for success and replication factors
for low performing actors. Some key characteristics of the network map (NetMap, see below)
are the ability to i) identify who the stakeholders are, together with their roles and relationships
with each other; ii) identify misalignment in the communications between stakeholders; iii)
identify a potential leading champion in water quality monitoring and management; and iv)
prioritize actions based on the highest negative influences in water quality management.
The NetMap exercise is only effective if the right stakeholders are present to map as
comprehensively as possible the stakeholders and flows. The resulting social network analysis
maps represent a subjective reality. For example, during the exercise, the participant who
represented the Basin Management Center Sumatra II (BWS Sumatera II) was actively
involved and participating, showing his keen interest in the WQ Roadmap for Lake Toba. Thus,
it may be shown in the NetMap that BWS Sumatera II had many more connections or linkages
compared to the linkages of other actors, while in reality this may be the same.
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H-4
Hence, it is difficult to achieve quantitative results with social network analysis. However, just
because the map does not represent an objective reality, it does not mean that stakeholders
are not making decisions and acting based on that reality. The network map should be seen as
a starting point for the understanding social landscape connectivity. The social network analysis
produces an important map to guide governance interventions. Moreover, the process provides
an important opportunity for reflection. The discussions that arise from the act of producing the
maps are an essential part of the learning process. It is, therefore, important to record
reflections and be cognizant of what has been learned during the process and also what
knowledge gaps still exist.
The process gives an opportunity to the participants to think about their own programs and
initiatives related to the lake management. For instance, at the second exercise, the provincial
and district services were prompted to think about who they should go to for direction, advices
and guidance on their planned activity.
H.2 Methods and tools
H.2.1 NetMap
The relationships between actors influencing the management of Lake Toba’s water quality
were defined and analysed with NetMap. The stepwise approach in NetMap (Figure H.3) was
elaborated into specific questions that would help increase understanding of the positions and
structural patterns of the stakeholders around Lake Toba.
Figure H.3, The six stages of mapping social network analysis in NetMap.
The specific guiding questions used in the stakeholder meetings were:
1. Who influences the water quality monitoring and management in Lake Toba?
2. Who are the stakeholders involved?
3. What are the types of links and how strong? (Authority, Funding, Information, Advice,
Advocacy, Pressure, Friendship)
4. How much interest do the stakeholders have in the issue?
5. How much influence do the stakeholders have?
The first question is defined as ‘who influences,’ rather than ‘who should be involved’. This
helps to identify those stakeholders that may have positive as well as negative impacts on the
water quality management. In the identification of stakeholders, all participants brainstorm
together and then create categories according to functions and roles.
Two NetMap exercises have been organized with two different groups to define and analyse
the relationships between actors influencing the management of Lake Toba’s water quality. The
1. Define Question
2. Identify Actors
3. Allocate Links
4. Assign Interest
5. Assign Influence
6. Input data
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first net map exercise was conducted in Jakarta on May 17, 2017 with the reference group,
where about 20 representatives actively participated in the process. The second net map
exercise was done in Laguboti, North Sumatra on June 14, 2017, with both the reference group
and participants at the local level, including representatives from provincial and district
agencies, local NGOs, the private sector, and local communities. The second net map exercise
was based on the result of the first net map exercise. There were about 50-60 participants at
this meeting. The involvement of the reference group and the participants in both meetings
provided an opportunity for a participatory approach. It allowed reflection and discussion on
many elements of the management of Toba Lake Water Quality, and contributed to a broader
understanding of the dynamics in the management of water quality in Toba.
To identify the actors that are involved in Lake Toba water quality management, a brainstorm
on paper was held with all the actors, after which some categories were created. Alll the
stakeholders with a similar role were put in the social landscape of Lake Toba in the same
category. These categories include: national government agencies, sub-national government
agencies, non-governmental organizations, local communities, academic institutions, and the
private sector.
Subsequently, the stakeholder names were written on post-it notes; each category of
stakeholders was assigned a single post-it notes colour. The list of stakeholders was confirmed
by the participants of the reference group and continued to be added throughout the exercise.
In the resulting map, red represents national government agencies, orange represents
subnational government agencies, purple represents non-governmental organization, green
represents local communities, pink represents academic institutions, and blue represents the
private sector and state-owned enterprises.
These post-it notes were then put on a dry-erase glass wall (Figure H.4). Once the actors and
actor groups had been defined, two important flow types were identified between the actors
relevant to Lake Toba water quality: authority and information (or coordination). These flows
were then drawn on the glass wall. Blue-coloured flows represent authority and red flows
represent information (or coordination). Formality of flows was represented with solid lines for
formal flows and dotted lines for the informal ones. Influence of the actors was determined by
the size of the circle of each actor. During the discussion, the participants also identified
stakeholders that have negative interests. The data were then entered into NodeXL and further
analysed.
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Figure H.4, NetMap Exercise with the Reference Group
There are many stakeholders who influence the water quality management of Lake Toba.
During the NetMap exercises, the participants were asked to think about the sources of
pollutants and the influencers in Lake Toba (such as aquaculture, wastewater, water supply,
solid waste, agriculture, erosion reduction, hydropower, and road infrastructure). Once they
started to think about these pollutant sources, they added and considered more actors
throughout this exercise.
Results from the collaborative NetMaps were analysed in NodeXL Basic software to produce a
quick perception of the social network visual. Node XL is fairly straightforward since it is an
add-on to the Excel program. Information can be copy-pasted from a previous Excel document
or written directly into the Node XL template. The sheets are organized separately for “Edges”
and “Vertices.” The headings of the columns are self-explanatory. NodeXL is user-frienly with
actors as input in a landscape on the “Vertices” sheet, and the relationships on “Edges” sheet.
Users can easily adjust the visual properties of the Vertices and Edges: the color, shape, width,
style, and visibility of each “Edge” and “Vertice” to show groups or similar interactions (Figure
H.5). Data can be shown as a circle or a vertical sine wave—each providing new perspectives
on connectivity between actors.
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Figure H.5, Example of stakeholder map visualisation (NetMap) in NodeXL software.
H.3 Stakeholder perceptions
H.3.1 Observations from NetMap discussions
Participants in the discussions on the NetMaps had many observations and suggestions that
are summarized below.
The discussions and resulting NetMaps illustrate that management of water quality in Lake
Toba is complex and dynamic. It also shows that to foster a change or intervene in the pollutant
control management, there are different sets of actors involved. For example, to enact change
in agriculture waste, the Agriculture District Services (or Dinas Pertanian) should be involved
because they could coordinate and give guidance to the Agriculture Communities (or
Komunitas Tani), while to manage pollutant loads from aquaculture, it has to go through
Fisheries Services (or Dinas Perikanan).
The maps show that the actors with many hubs (highly connected network) are mostly at the
central level. However, participants indicated that the many linkages connected to the actors
do not necessarily translate into a similar number of programs by each actor. Participants
indicated in the discussion that, in principle, the sub-national government should have more
roles in influencing management decisions of Lake Toba water quality (compared to the
national government). This is shown once interest and influence was assigned to the actors.
The participants agreed to assign sub-national actors with the highest influence, which is
reflected in Figure 4.1 and Figure 4.2 by the size of the circles.
At the second exercise at local level, the participants proposed to adjust the map by separating
the levels of actors at the subnational level into provincial level and district level. This was done
to better visualize the connection between levels, and where gaps could potentially exist. The
second map shows that there are few connections at the sub-national levels (both at the
provincial and district levels, but especially at the district levels), to the rest of the actors on the
map. It also seems that many of their connections are mostly with other governmental entities,
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and rarely with the private sector, academia, or others. It becomes more apparent that the sub-
national government, especially at the district level, often works in isolation – there is little
collaboration between agencies in different sectors, nor between various levels. Thus, this
might confirm findings from the first exercise, that the central level actors appear to be more
vocal and in practice, are more involved in terms of the management of Lake Toba.
Not shown in the maps are the assigned interests of the actors in relation to the water quality
management of Lake Toba. During the discussion, the participants brought up some of the
actors that may have very little interest in improved water quality management or pollution
control. They mentioned: aquaculture farmers (PT Aquafarm Nusantara, PT Suri Tani Pemuka),
hotel owners and household owners, agriculture and livestock farmers, forest enterprises, as
the biggest negative influencers (or polluters) of the water quality of the Lake Toba. Others
such as miners, lake transportation actors were also mentioned as having negative influence,
but with less prominent influence as the former actors.
There are many coordinating bodies (Forum DAS, TKPSDA, and BKEPDT) to manage the
water quality of Toba but the map does not show any clear leader or champion. These
coordinating bodies are also initiated by the central ministries and/or provincial governors, with
little focus given at the district levels, even though they were intended to accommodate district
services as well. In addition to these coordinating bodies, there are many hubs (or connections)
between actors, but no leading actors who supervise the management. The hubs indicate the
potential of these actors to be the champions of change toward the better management of Lake
Toba water quality. However, the hubs do not directly translate to the many initiatives by these
actors. Rather, they show that there are flows of information in the actors, but initiatives are still
lacking, especially from the sub-national level. The participants at both exercises confirm the
need to have a clear leader and champions. It is important to note that a champion or
management leader ideally has a capacity and linkage to many different types of institutions
and at different levels.
Many of the civil society organizations (CSOs), such as Yayasan Pencinta Danau Toba
(YPDT), WALHI, Alusi Tao Toba, KSPPM, and local communities, represented through
DAERMA (Local Fishermen’s Association), expressed that often when their aspirations are not
well-received by the district services, they would go directly to the relevant ministries at the
national level. It might be worth to explore the CSOs’ potential to guard the management
process of Lake Toba or be an agent of change, considering their active participation and
monitoring on the issue, and their close relationships (formal and informal) with different kinds
of stakeholders. From the discussion at the second workshop, the CSOs emerged as having
been engaging with each other as well as with the local communities, and as having been
pressuring many changes to the government and to private sector as well.
H.3.2 Summary of stakeholder comments
According to the stakeholders, good regulations are available but not always coordination, while
implementation is not being monitored systematically. These have to be followed up by clearer
guidance to be easy implemented (example: Spatial Plan in Province level has to followed up
by Spatial Plans in District level or to be elaborate in technical and implementing guidance).
Communication of new regulations could also be improved. Monitoring in implementation of
regulations has to be enforced and could be done by overlaying actual conditions and
requirements in regulation. Instruction letters would be useful for this and help guide program
implementation (especially in putting budget for implementation; example SSE Home Affairs).
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A contribution factor would be to base the issuance of permits on technical recommendations
by relevant district agencies.
During the interviews conducted with provincial and national institution as part of this
assessment, various stakeholders (in particular PU and forestry) indicated that broad
cooperation and acceptance of the recommendations by the Districts is required for successful
implementation of the WQ Roadmap. This includes clear support and direction by the Ministry
of Home Affairs, which has the mandate and authority to give direction to the Districts. Since
1998, most of the proposed programs and interventions lacked this support, according to the
stakeholders. Key members of the Reference Group consider this lack of local linkage and
embedment (with also no “active” agreement on the National level with the Ministry of Home
Affairs) as one of the main “dysfunctional features” or “bottlenecks” for the implementation of
their different well-formulated and urgently-required programs to safeguard and improve the
environment and water quality of Lake Toba.
Similarly, while officially (de jure; chapter 3) institutions have a mandate in water quality, in
reality (de facto; chapter 0) institutions with clear mandates do not necessarily have the most
impactful program. As a result, there is an institutional gap as no organization acts as a leader
in water quality management: not in monitoring, and not in implementation. Community-based
organizations could play a role, but need adequate support.
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I Comprehensive list of stakeholders involved in Lake Toba water quality
Table I.1 presents all stakeholders, identified during the stakeholder consultation process,
that use or influence Lake Toba. Those marked as regulator and/or operator, play a role
in water quality monitoring.
Table I.1, Institutions with a stake in Lake Toba, along with their roles (members of the Reference Group are
marked in yellow).
Institutions/ lembaga
stakeholder role
Regu
lato
r
Opera
tor
Develo
per
Coord
inatio
n
User
NATIONAL
Coordinating Min. of Maritime Affairs R C
Coordinating Min. of Economy R
Min. of Tourism R C
Min. of Home Affairs (cq DG Regional Development) R
National Planning Agency/Bappenas (Sub Dit. River, Coastal, Reservoir, Lake)
R C
Min. of Finance R
Min. of Environment and Forestry R
Min. of Agraria and Spatial Planning R
Min. of Public Works and Housing R O D
- Development Body Region Infrastructure (BPIW) R C
- Dit. Gen Human Settlements - PPLP R
- Dit. Gen of Bina Marga R
- Dit.Gen Water Resources (cq Dit Rivers and Coastal) R
- Center of Dam/reservoir (cq Lake, Situ, Embung division)
R D C
- Center of raw water and ground water R
- BWS Sumatera II R O D
- Center Research of Water Resources R
Min. of Transportation R
Min. of Marine Affairs and Fisheries R
Min. of Energy and Mineral Resources R
Min. of Manpower R
Min. of Aparatur State Utilization (bureaucracy reform) R
Secretary of Cabinet/Presidential Chief of Staff office R
Min. Of Agriculture R
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Institutions/ lembaga
stakeholder role
Regu
lato
r
Opera
tor
Develo
per
Coord
inatio
n
User
Min. of Industry R
LIPI Research Center of Limnology R
BPPT R
Min. State Own – PJT1 O
Badan Meteorologi Klimatologi & Geofisika (BMKG) O
Badan Nasional Penanggulangan Bencana (BNPB) R O
Badan Otorita Pariwisata Danau Toba O D C U
PROVINCE
Governor of North Sumatra R
Regional Planning Agency/Bappeda Prov R C
Prov. Forestry R O
Prov. Environmental Services R O C
Prov. Water Resources Services R O
Prov. Human Settlements TR Services R O
Land Cadaster/bpn atr Prov R O
Prov. Services of Transportation R O
Prov. Agriculture R O
PPL (Petani Penyuluh Lapangan) O
Prov. Fisheries services R
PPL (Penyuluh Lapangan Perikanan) O
Prov.. Tourism Services R O
Badan Penanggulangan Bencana Daerah (BPBD) O
Badan Pengelola Geopark Kaldera Danau Toba O C U
KABUPATEN/DISTRICTS (8)
Head of District R
Regional Planning Agency/Bappeda Kab. R C
Kab. Forestry R O
Kab. Environmental Services R O C
Kab. Water Resources Services R O
Kab. Human Settlements TR Services R O
Land Cadaster/bpn atr District R O
Kab. Services of Transportation R O
Kab. Agriculture R O
PPL (Petani Penyuluh Lapangan) O
Kab. Fisheries services R
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Institutions/ lembaga
stakeholder role
Regu
lato
r
Opera
tor
Develo
per
Coord
inatio
n
User
PPL (Petani Penyuluh Lapangan) Perikanan O
Kab. Tourism Services R O
STATE OWNED, private sector, civil society, NGO
Perhutani O U
Masyarakat Adat (Batak) U
AMAN (Aliansi Masyarakat Adat Nasional) U
WALHI North Sumatra U
Yayasan Pencinta Danau Toba U
Community Masyarakat Peduli Danau U
Forum Komunikasi Danau Toba U
KSM (Kelompok Swadaya Masyarakat) U
PKK (Pembinaan Keluarga Sejahtera) U
Forest communities (upstream conservation) U
Other NGOs (KSPPM, Alusi Tao Toba, Hutan Rakyat Institute)
U
Fishermen’s Association (DAERMA) + others U
Tourism communities U
Rivers communities U
Universities/Perguruan Tinggi – USU (North Sumatra University) - UNIMED, Nomensen - Universitas Simalungun
U
URI (University Rhode Island) U
Electricity company: INALUM + PLN + others U
Bajradaya Sentranusa (BDSN) U
Industrial group/area industry U
TPL (Toba Pulp Lestari) U
PT Aquafarm Nusantara U
Suri Tani U
Kelompok Tani U
Kelompok Pembudidaya Ikan U
Asosiasi Peternak U
Irrigation Commission/Komisi Irigasi U
WUA/Group WUA/Federation WUA U
Komunitas transportasi air U
Penambang Galian C U
DMO Toba U
Public Water Supply Company/PERPAMSI - PDAM U
Coordination Body
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Institutions/ lembaga
stakeholder role
Regu
lato
r
Opera
tor
Develo
per
Coord
inatio
n
User
Coordinating Body on Capital investment/BKPM C
National Water Resources Council/Dewan Sumber Daya Air Nasional
C
Provincial Water Resources Council/Dewan Sumber Daya Air Provinsi
C
BKPEDT C
Basin Council/Tim Koordinasi Pengelolaan Sumber Daya Air Wilayah Sungai
C
Forum DAS (Daerah Aliran Sungai) C
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J Detailed methodology lake assessment
J.1 Sumatra Spatial Model
J.1.1 Introduction
Strong demographic changes and increasing economic activities over the next (25) years
will stretch available resources of land, water and environment on many Indonesian islands
to the limit. Settlement and non-adapted land-use practices up to now have had a strong
impact on many sectors. For the water sector adverse impact on runoff, such as higher
peak flows and lower low flows, are being experienced, resulting in increased flooding and
shortages in water supply. For agriculture, the high demand for new urban land will result
in a loss of valuable irrigated land. In these circumstances, an effective protection through
zoning and regulation will be necessary to protect the interest of different sectors and
allocate urban development to less harmful locations. For water such conservation policy,
via a spatial zoning policy, should prevent further degradation of water resources and
upgrade as much as possible existing adverse conditions.
The spatial law Nr 26 (2007), with its orientation to sustainable resource management and
protection provides a framework to develop and implement spatial planning within
Indonesia (Figure J.1). For example for the water sector, the New Spatial law specifically
addresses conservation specifies as a minimum target of maintaining 30% of forest in each
water catchment area (DAS). Similar land claims or zoning policies are being specified for
other sectors like agriculture, forestry, housing, and environment. The Ministry of
Agriculture has adopted law nr. 41 (2011) on food security. The land requirements from
relevant sectors should be integrated in the spatial plans as many regions in Indonesia
suffer from a shortage of suitable land resources.
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Figure J.1, Land use according to Rupa Bumi (BIG).
The basis for the land use data in the Sumatra Spatial Model is the Peta Rupa Bumi
Indonesia from BIG (Figure J.2). This dataset however is often out of date and in practice
corrections have been made for the paddy fields (based on the 2010 Peta Audit Baku
Sawah from the Ministry of Agriculture) and the urban area (Google Maps). In particular, it
was found that some of the categories near Lake Toba needed correction to get
representative starting situation for the land use per village (desa).
If large land claims are developed for a sector then this will have strong impact on other
land consuming sectors (e.g. urbanization will grow at the expense of other sectors). To
analyse these effects a quantitative approach is needed that models spatial changes in
population, employment, urban land-use and associated changes in land-use. Such a
spatial model, the Sumatra Spatial Model, is presented here.
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Figure J.2, Lake Toba Region Spatial Plan (Presidential decree 81/2014).
The first version of the spatial model was developed for the island of Java: the Java Spatial
Model or JSM. JSM 1 was first developed under the BWRMP project in 2001-2002 and
further developed in the “Space and Water” project (2006-2008), see also Vernimmen
(2015). The latter is a spatial planning initiative covering all of Java, to support integration
of spatial planning with water resources planning, and JSM 1 proved its usefulness there.
Coverage of whole Java is necessary to reflect the migration flows on Java. In the 6Ci
project for the ADB the model has been updated to JSM 2.0, 2.1 and 2.2. The spatial
model provides internally consistent future projections of:
• The spatial distribution at village level of the population and employment;
• The urban area growth needed to accommodate human activities; and
• The land-use changes caused by the urban area growth.
JSM provides in particular a consistent projection of urban/rural land-use with important
consequences for total water demand, water quality and ecology, based on:
• Socio-economic projection of population/employment at district (kabupaten) level based on economic growth scenarios,
• Spatial allocation of population and land-use for Java at village (desa) level,
• Calculation of impacts, such as water demands, and pollutant emissions at different geographic levels (the River Basin Territories or parts thereof; Water districts; province; districts, sub-districts and villages). The calculation is based on existing Ministry of Public Works (MPW) guidelines for river basin studies.
In 2015 and 2016 the spatial model was applied to Sumatra (SSM) in the Sumatra Water
Resources Strategic Study and to Sulawesi in the Sulawesi Water Resources Strategic
Study (SulSM).
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J.1.2 Land use changes
The on-going transformation of non-urban area into urbanized land is the result of
developments in spatial markets like the housing market, labour market or transport
market. These markets change under influence of several interacting driving forces;
important drivers are demographic and socio-economic drivers. A good understanding of
these drivers, how they are going to develop and differ among regions, is important for
predicting future urban land-use. Demographic drivers are especially important to project
future residential land demand. Key drivers for additional urban land-use are:
• Domestic land use change is caused by: o Population growth; o Household size reduction; o Increasing use of land resources per household as wealth grows.
• Municipal and industrial land use is caused by: o Economic growth; o Employment growth; and o Change in economic structure
These drivers of land use steer the design of the Sumatra Spatial Model (Figure J.3). The
key design principles are:
• Two step approach to capture the different spatial trends of centralization at an interregional (kabupaten) level and suburbanization (or decentralization) within a region (desa level);
• The modelling is dynamic and uses time steps of one year; this reflects the incremental nature of spatial changes and enables to model the time path dependency of developments;
• Key feature of the model is its spatial detail, the model is capable of calculating the impacts on the spatial distribution of residents/employment and associated land-use changes of different socio-economic (or demographic) scenarios and/or policies at the level of desa units.
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Figure J.3, Overview of the Sumatra Spatial Model, as originally applied to Java.
J.2 Modules and variables
The model consists of three modules (Figure J.4):
Module 1: Regional module
• Calculates at district (kabupaten) level population growth and migration. Sum of population of all districts on the island (Sumatra) is kept equal to available official (BPS/BAPPENAS) population projections and economic growth scenarios.
Module 2: Land-use allocation module
• Allocates space demand at kabupaten level to desa level based on preferences of residents and zoning policy.
Module 3: Spatial development & water resources indicators
• Land-use changes at different administrative levels
• Water resources impacts
• Agricultural and food supply impacts
• Ecological Impacts
Spatial Plan
Kabupaten
Socio-economic
model
Desa land
allocation model
Start population,
employment, GDP
Postprocessor
impact indicators
Drivers:
Java population. Growth etc
Start land
use data
Input
parameters
Kabupaten results
Desa results
Impacts
Administrative regionWatersheds
Water districts
etc
Tim
e l
oop
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Figure J.4, Application concept for the Sumatra Spatial Model.
J.2.1 Regional or Socio-economic sub-model
The socio-economic sub-model handles the projections of population and industrial
activities. It uses four model sectors: population, employment, housing and industry. The
idea is that these sectors represent the major urban development processes. Between the
three economic sectors (agriculture, industry and services) there are various feedbacks
that influence the rates of change within the sectors. The distribution of the (growing)
population depends on the attractiveness of an area (e.g. number of available jobs) and is
constrained by limited resources (e.g. land). These two assumptions mean that growth is
limited in the end by available land.
The different model sectors are related to each other, values for model variables in one
sector will affect the values of model variables in other sectors. For example construction
of new industrial structures will result in more jobs. New jobs will attract people from
outside the region and the immigration will increase. A larger population size will result in
a higher demand for housing and construction of new houses will be the result. This growth
loop will be limited by the availability of land.
The sub-model predicts population developments (growth & migration) at the district
(kabupaten) level, based on a basic linkage between economic developments and
population developments. Explanatory variables are developments in gross regional
product, employment, regional features (e.g. land availability) and proximity. Key data
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source for calibration of this sub-model is the Dalam Angka data and Census 1990/2000
data of BPS. This has been collected for the time period 1990-2010. At district (kabupaten)
level census 2010 data were obtained for calibration.
The regional model consists of a simple shift/share procedure to allocate province level
economic growth scenarios over the districts. A more elaborated procedure (shift/share in
combination with regional explanatory variables) calculates the population developments
for each of the districts and explains the differences in development between the districts.
J.2.2 Spatial allocation sub-model
The spatial allocation sub-model predicts how the calculated growth of activities of the
social-economic sub-model is spatially distributed within the study area and what the
resulting land-use changes are. The allocation model distributes the land demand of the
social-economic model to different parts within the region. The available land in the
different areas (cells) will be subject of inventory and the attractiveness of this area for the
land demanding activities. The available land for the allocation process depends on the
land-use in the area. The attractiveness of an area for a specific activity is a combination
of the characteristics of the area and the preferences of the activities. This parameter is
called the attractiveness potential of an area. Every time step the new activities are
allocated to the areas. After the allocation the new situation will be stored in the database
and will function as starting point of the next time step. An overview of the applied
attractiveness criteria is given below:
1. Accessibility: In almost all spatial models the accessibility of a spatial unit plays an
important role in the allocation of functions. Good accessible areas are attractive as location for residential and industrial land use. The accessibility criterion gives a value for how far it is from the center of a cell to the closest main road. The accessibility is normally calculated as the average time needed to travel from inside the desa to the main road. Due to lack of time and available data the indicator is based on four accessibility classes.
2. Access to work: This indicator represents the accessibility of work from a certain
location. In other words are there enough jobs within a reasonable travel time. This requires a travel time matrix from a transport model. The Lake Toba model does not use this indicator.
3. Proximity (gravity criterion): This criterion is a parameter for the distance of an area to
urban and economic activities. This criterion refers to spatial regularities as movement-minimization and the tendency to agglomerate. The idea behind this criterion is that an area close to urban or economical centers is more attractive than an isolated area that is far away (see the example of Java in Figure J.5). This is similar to attractive forces of high density mass or gravity. Variables included in this criterion are the distances between areas, the number of inhabitants and jobs in the area.
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Figure J.5, Example of proximity indicator for Java.
4. Planning zones, governmental influence: Planning zones are spatial zones defined by
the government where specific land-use plans or restrictions exist. The knowledge of which area is in which planning zone can be obtained with an overlay analysis. The importance of a planning zone for a land demanding function can be managed in the weight set. For example an area within the zone where industrial development is allowed will have a positive value for this criterion in the allocation of new industries. Restriction of urban development, e.g. for reasons of food security, will have a negative value for the attractiveness for housing.
5. Land price and land development cost: Due to limitations in available data the indicator
is based on six classes. Each class represents a group of land price and land development costs. This indicator is a proxy for land suitability for urbanisation.
6. Attractivity or aesthetic value: The indicators mentioned above result in the attractivity
indicator for each desa. By giving each indicator a weight and making a weighed summation the attractivity for each desa for housing and industry is calculated.
J.2.3 Postprocessor for space, water and agricultural indicators
This sub-model calculates indicators as inputs to Basin Water Resources Management
Planning and other sectoral resources impact assessments. It is described in more detail
in the next section. Outputs of the sub-model are:
A. Spatial indicators (directly from the allocation module):
• Population and population density
• Fraction of areas by land use class
B. Water demands:
• Domestic Municipal and Industrial demand (DMI)
• Irrigation
C. Wastewater emissions (BOD):
• Domestic, Municipal and Industrial emissions
• Irrigated paddy
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D. Biodiversity:
• Mean species abundance (MSA) loss due to urbanisation
E. Rice, vegetable and palawija crop production, consumption and self-sufficiency
J.3 Spatial results by compartment and year
Table J.1, Overview of spatial results in 2018, 2022 and 2042 for Lake Toba as a whole.
Variables Whole Lake
2018 2022 2042
Metropolitan population 0 0 0
Large town population 0 0 0
Medium town population 0 0 0
Small town population 0 0 0
Kecamatan city population 42,468 43,547 46,896
Desa population 438,622 475,637 585,531
Employment 209,528 223,243 338,761
Households 118,610 129,903 173,747
Housing (ha) 10,964 12,155 16,628
Other buildings (ha) 1,534 1,751 4,105
Rainfed paddy (ha) 0 0 0
Technical Irrigated Paddy (ha) 17,188 17,062 16,443
Semi-technical Irrigated Paddy (ha) 11,459 11,374 10,962
Other agriculture (ha) 80,397 79,876 77,480
Grass/Other (ha) 10,871 10,748 10,243
Shrub (ha) 54,168 53,950 52,831
Forest (ha) 62,406 62,305 61,795
Ponds (ha) 0 0 0
Plantation (ha) 32,627 32,407 31,403
Water (ha) 3,575 3,575 3,575
Total urban area (ha) 12,497 13,906 20,732
Total irrigated paddy area (ha) 28,647 28,436 27,405
Sum of remaining area available for land use change (ha) 197,534 196,125 189,299
Total area (ha) 294,052 294,052 294,052
Total population 481,090 519,184 632,426
HouseAreaNeeded (ha) 0 0 0
IndustryAreaNeeded (ha) 0 0 0
HouseAreaVacated (ha) 0 0 0
IndustryAreaVacated (ha) 0 0 0
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Table J.2, Overview of spatial results in 2015, 2018, 2022 and 2042 for two compartments of Lake Toba.
Variables North South
2018 2022 2042 2018 2022 2042
Metropolitan population 0 0 0 0 0 0
Large town population 0 0 0 0 0 0
Medium town population 0 0 0 0 0 0
Small town population 0 0 0 0 0 0
Kecamatan city population 19,138 19,770 21,740 23,330 23,777 25,155
Desa population 124,803 137,582 175,930 313,819 338,055 409,600
Employment 65,208 69,478 105,950 144,321 153,765 232,812
Households 35,522 39,133 53,465 83,089 90,770 120,282
Housing (ha) 3,712 4,323 6,635 7,252 7,832 9,992
Other buildings (ha) 521 622 1,693 1,012 1,130 2,411
Rain-fed paddy (ha) 0 0 0 0 0 0
Technical Irrigated Paddy (ha) 2,187 2,156 2,012 15,001 14,905 14,431
Semi-technical Irrigated Paddy (ha)
1,458 1,438 1,341 10,001 9,937 9,621
Other agriculture (ha) 21,592 21,331 20,188 58,805 58,545 57,292
Grass/Other (ha) 2,938 2,847 2,485 7,933 7,901 7,758
Shrub (ha) 17,330 17,218 16,652 36,838 36,732 36,180
Forest (ha) 27,005 26,933 26,565 35,401 35,373 35,229
Ponds (ha) 0 0 0 0 0 0
Plantation (ha) 3,632 3,522 3,061 28,995 28,885 28,342
Water (ha) 1,626 1,626 1,626 1,949 1,949 1,949
Total urban area (ha) 4,233 4,945 8,329 8,264 8,961 12,404
Total irrigated paddy area (ha) 3,645 3,594 3,353 25,002 24,842 24,052
Sum of remaining area available for land use change (ha)
53,089 52,378 48,994 144,445 143,748 140,305
Total area (ha) 90,217 90,217 90,217 203,835 203,835 203,835
Total population 143,941 157,352 197,670 337,149 361,831 434,756
HouseAreaNeeded (ha) 0 0 0 0 0 0
IndustryAreaNeeded (ha) 0 0 0 0 0 0
HouseAreaVacated (ha) 0 0 0 0 0 0
IndustryAreaVacated (ha) 0 0 0 0 0 0
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Table J.3, Overview of spatial results in 2015, 2018, 2022 and 2042 for four compartments of Lake Toba:
North and South 1.
Variables N S1
2018 2022 2042 2018 2022 2042
Metropolitan population 0 0 0 0 0 0
Large town population 0 0 0 0 0 0
Medium town population 0 0 0 0 0 0
Small town population 0 0 0 0 0 0
Kecamatan city population 19138 19770 21740 4844 4960 5317
Desa population 124803 137582 175930 35847 38672 47115
Employment 65208 69478 105950 20666 22026 33413
Households 35522 39133 53465 10130 11094 14791
Housing (ha) 3712 4323 6635 1021 1088 1337
Other buildings (ha) 521 622 1693 174 190 362
Rain-fed paddy (ha) 0 0 0 0 0 0
Technical Irrigated Paddy (ha) 2187 2156 2012 944 942 930
Semi-technical Irrigated Paddy (ha) 1458 1438 1341 629 628 620
Other agriculture (ha) 21592 21331 20188 11600 11551 11302
Grass/Other (ha) 2938 2847 2485 1543 1539 1518
Shrub (ha) 17330 17218 16652 5652 5632 5529
Forest (ha) 27005 26933 26565 10784 10782 10772
Ponds (ha) 0 0 0 0 0 0
Plantation (ha) 3632 3522 3061 1404 1400 1383
Water (ha) 1626 1626 1626 130 130 130
Total urban area (ha) 4233 4945 8329 1195 1278 1700
Total irrigated paddy area (ha) 3645 3594 3353 1573 1569 1551
Sum of remaining area available for land use change (ha)
53089 52378 48994 18598 18515 18093
Total area (ha) 90217 90217 90217 33946 33946 33946
Total population 143941 157352 197670 40691 43632 52432
HouseAreaNeeded (ha) 0 0 0 0 0 0
IndustryAreaNeeded (ha) 0 0 0 0 0 0
HouseAreaVacated (ha) 0 0 0 0 0 0
IndustryAreaVacated (ha) 0 0 0 0 0 0
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Table J.4, Overview of spatial results in 2015, 2018, 2022 and 2042 for four compartments of Lake Toba:
South 2 and South 3.
Variables S2 S3
2018 2022 2042 2018 2022 2042
Metropolitan population 0 0 0 0 0 0
Large town population 0 0 0 0 0 0
Medium town population 0 0 0 0 0 0
Small town population 0 0 0 0 0 0
Kecamatan city population 3668 3761 4035 14818 15056 15804
Desa population 160417 171956 203774 117555 127426 158712
Employment 83023 88394 132849 40631 43345 66550
Households 39572 43081 56103 33388 36595 49387
Housing (ha) 3606 3942 5152 2624 2802 3503
Other buildings (ha) 445 514 1271 394 426 779
Rain-fed paddy (ha) 0 0 0 0 0 0
Technical Irrigated Paddy (ha) 6731 6687 6475 7326 7276 7026
Semi-technical Irrigated Paddy (ha)
4488 4458 4317 4884 4851 4684
Other agriculture (ha) 40560 40376 39507 6645 6618 6483
Grass/Other (ha) 4403 4382 4289 1987 1981 1951
Shrub (ha) 25401 25327 24939 5785 5773 5712
Forest (ha) 18151 18132 18031 6465 6459 6427
Ponds (ha) 0 0 0 0 0 0
Plantation (ha) 6699 6668 6520 20892 20817 20440
Water (ha) 1589 1589 1589 231 231 231
Total urban area (ha) 4051 4456 6422 3018 3228 4282
Total irrigated paddy area (ha) 11219 11146 10792 12210 12127 11710
Sum of remaining area available for land use change (ha)
81817 81411 79445 44031 43821 42767
Total area (ha) 112591 112591 112591 57297 57297 57297
Total population 164086 175717 207809 132372 142482 174515
HouseAreaNeeded (ha) 0 0 0 0 0 0
IndustryAreaNeeded (ha) 0 0 0 0 0 0
HouseAreaVacated (ha) 0 0 0 0 0 0
IndustryAreaVacated (ha) 0 0 0 0 0 0
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J.4 Calculation of nutrient concentration trajectories
Total nitrogen (TN) and total phosphorous (TP) concentrations are calculated in a simple
budget model approach. In this model the total nutrient concentration in a water body is
determined by the loading, the lake’s area and mean thermocline depth, the flushing rate,
and the fraction of nutrients retained in the water column:
C = L / (Q + k * A * d)
In which:
C = the calculated concentration (µg/l)
L = the nutrient load as calculated in the section above (µg/d)
Q = outflow (m3/d)
k = retention rate (1/d)
A = surface area (m2)
d = thermocline depth (m)
The above budget model is a modification of the models in previous Lake Toba carrying
capacity studies (Oakley 2015; LIPI, EPANS, CFM, 2014). Ultimately this budget model
approach stems from the widely used empirical model of Dillon & Rigler (1974), developed
to predict the response of aquatic ecosystems to increases in P loadings.
The outflow varies between 90 and 140 m3/s (Vernuimmen, 2015; section 2.2.1; Annex
B.5). In the model, this value is set at 110 m3/s; a combination of long term average and
extrapolation of trends. On the total volume of Lake Toba, the exact value of outflow has
minimal impact on the resulting concentrations. The effect is the same in the
compartments.
Figure J.6, The effect of changing lake outflows on concentrations of total phosphorous (P) in Lake Toba, for
the whole lake compartment.
Note that the budget model approach is an over-simplification of reality, which does not
take into account the complexity of physical and biogeochemical processes, nor their
variability in time and space. The model does therefore not provide any system
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understanding, nor provides any predictions about future changes in physical or
biogeochemical processes. The compartment approach addressesat least some of the
spatial variability present in Lake Toba. Also, the sensitivity for the thermocline depth is
explored. For more precise computations and predictions, it is recommended to use a 3D
ecosystem model.
J.5 Comparison to LIPI data
Results from the Sumatra Spatial Model were compared to findings from LIPI, such as
their 2010 study that describes the trophic state of 19 different measuring points along the
coast line of Lake Toba. The state is determined by measuring a series of parameters:
Total Organic Matter (TOM), Dissolved Organic Matter (DOM), Phosphate Organic Matter
(POM), Total Nitrogen (TN), Dissolved Oxygen, Temperature (Suhu), pH, and Conductivity
(LIPI 2013; Figure J.7). The values in the table of Figure J.7 correspond well with the PTAN
figures.
Figure J.7, LIPI data set 2010. Various parameters measured at 19 different locations in April of 2010. See
table on the right for values of different measurements (Figure provided by LIPI).
Another study conducted by LIPI in 2013 that TN concentrations measured in 2013 vary between 0.075 and 0.374 mg/l (Figure J.8), which corresponds well with the amounts mentioned in chapter 6. Station 7 and 8 (with concentration of 0.238 and 0.302 mg/l) are those closest to the measuring points of PTAN.
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Figure J.8, LIPI data set 2013. Various parameters measured at 19 different locations in August and October
of 2013 (Figure provided by LIPI).
14
13
15
16
11 12
10
17
18
19
9 1
2
8 6
Asa
han 3 4
7 5
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K Available data and their quality
K.1 Data collected from stakeholders
Many stakeholders provided data relevant for this study, such as catchment-wide GIS data on
land use, population statistics, agricultural statistics or lake monitoring data such as nutrient
concentrations, water transparency and chlorophyll concentrations. Table K.1 summarizes the
data, collected from the stakeholders, which have been included in the lake and catchment
assessment.
In environmental monitoring data fall in three functional categories, or levels, with significant
differences in monitoring effort:
1. Monitor environmental status (signal function)
2. Explain environmental phenomenon (exploratory)
3. Scientific, statistically sound analysis or modelling The usability of data differs per topic, question, or focus. Therefore, the general usability indicator was assigned per topic: trophic status, water balance, hydrodynamic modelling (3D), estimating nutrient inputs form the catchment and lake activities (nutrient loading), lake carrying capacity, and estimating catchment erosion load (erosion).
Table K.2 shows - data usability assessment for the available reference group data, inthe three
functional categories identified in the inception report. As much as possible and pending approval by data owners, the various data and literature collected in the course of this assignment are made available to the Reference Group. In that way, all participants can benefit from the aggregated and collective data.
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Table K.1, Overview of types of data collected by stakeholders of Lake Toba. The cells marked green depict data received by the consultant (in any form).
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Table K.2, Data assessment based on three functional categories (1) signal function; (2) exploratory data; (3)
statistically conclusive. The assessment is given for overall and for 6 applications. Not all data may apply to
all applications.
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K.2 Completeness of the data sets
To assess the completeness of the water quality data sets collected by the institutions
described in section 3.3, the data have been compared to the monitoring guideline set up by
Chapman (1996). His table indicates the water quality parameters that are relevant for various
issues (Table K.3). The marks indicate the likelihood that the concentration of the parameter
will be affected. If so, it is more important to include the variable in a monitoring program.
Variables stipulated in local guidelines or standards for a specific water use should be included
when monitoring that specific use. Of main interest to the underlying assessment are the
‘background monitoring’ and ‘aquatic life and fisheries’ (highlighted columns).
Table K.3, Selection of variables for assessment of water quality in relation to non-industrial water use (adapted
from: Chapman, 1996). Rating x to xxx: low to high likelihood that the concentration will be affected and low
to high importance to include the variable in a monitoring program. Background monitoring
Aquatic life and fisheries
Drinking water
sources
Recreation and health
Agriculture
Irrigation Livestock watering
General parameters
Temperature xxx xxx
x
Colour xx
xx xx
Odour
xx xx
Suspended solids xxx xxx xxx xxx
Turbidity/transparency x xx xx xx
Conductivity xx x x
x
Total dissolved solids
x x
xxx x
pH xxx xx x x xx
Dissolved oxygen xxx xx x
x
Hardness
x xx
Chlorophyll a x xx xx xx
Nutrients
Ammonia x xxx x
Nitrate/Nitrite xx x xxx
xx
Phosphorous or phosphate xx
Organic matter
TOC xx
x x
COD xx xx
BOD xxx xxx xx
Major ions
Sodium x
x
xxx
Potassium x
Calcium x
x x
Magnesium xx
x
Chloride xx
x
xxx
Sulphate x
x
x
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Background monitoring
Aquatic life and fisheries
Drinking water
sources
Recreation and health
Agriculture
Irrigation Livestock watering
Other inorganic variables
Fluoride
xx
x x
Boron
xx x
Cyanide
x x
Trace elements
Heavy metals
xx xxx
x x
Arsenic & selenium
xx xx
x x
Organic contaminants
Oil and hydrocarbons
x xx xx x x
Organic solvents
x xxx
x
Phenols
x xx
x
Pesticides
xx xx
x
Surfactants
x x x
x
Microbiological indicators
Feacal coliforms
xxx xxx xxx
Total coliforms
xxx xxx x
For this study the Chapman table has been adapted and filled with water quality parameters
have been measured by DLH-SU, LIPI, and PTAN (Table K.4). For each variable, crosses
indicate whether a certain parameter was considered relevant (according to the Chapman
(1996) guideline) for background monitoring and/or aquatic life, but was not present in one of
these three data sets. All parameters for which data were available were highlighted.
Table K.4, Data availability of DLH-SU, LIPI and PTAN, with indication of relevance (according to the Chapman
guidelines). When x is used, the variable is not present in the data set.
BLH-SU LIPI PTAN
Variable locations
time frequency locations
time frequency
locations
time frequency
General parameters
Temperature 18-28 2006-2016
1-2 per year
12 2009 once 4 2006-2017
monthly
Colour xx/- xx/- xx/- xx/- xx/- xx/- xx/- xx/- xx/-
Odour 18-28 2006-2016
1-2 per year
Suspended solids 18-28 2006-2016
1-2 per year
xxx/xxx
xxx/xxx
xxx/xxx xxx/xxx
xxx/xxx xxx/xxx
Turbidity/transparency
18-28 2006-2016
1-2 per year
12 2009 once 4 2006-2017
monthly
Conductivity xx/x xx/x xx/x xx/x xx/x xx/x xx/x xx/x xx/x
Total dissolved solids 18-28 2006-2016
1-2 per year
-/x -/x -/x -/x -/x -/x
pH 18-28 2006-2016
1-2 per year
12 2009 once 4 2006-2017
monthly
Dissolved oxygen 18-28 2006-2016
1-2 per year
xxx/xx xxx/xx xxx/xx 4 2006-2017
monthly
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TOC: Total organic carbon
BOD: Biochemical oxygen demand
COD: Chemical oxygen demand
Hardness -/x -/x -/x -/x -/x -/x -/x -/x -/x
Chlorophyll a 18-28 2006-2016
1-2 per year
12 2009 once 4 2006-2017
monthly
Nutrients
Ammonia 18-28 2006-2016
1-2 per year
x/xxx x/xxx x/xxx 4 2006-2017
monthly
Nitrate/Nitrite 18-28 2006-2016
1-2 per year
12 2009 Once 4 2006-2017
monthly
Phosphorous or phosphate
18-28 2006-2016
1-2 per year
12 2009 once 4 2006-2017
monthly
Organic matter
TOC 18-28 2006-2016
1-2 per year
xx/- xx/- xx/- 4 2006-2017
monthly
COD 18-28 2006-2016
1-2 per year
xx/xx xx/xx xx/xx xx/xx xx/xx xx/xx
BOD 18-28 2006-2016
1-2 per year
xxx/xxx
xxx/xxx
xxx/xxx xxx/xxx
xxx/xxx
xxx/xxx
Major ions
Sodium x/- x/- x/- x/- x/- x/- x/- x/- x/-
Potassium x/- x/- x/- x/- x/- x/- x/- x/- x/-
Calcium x/- x/- x/- x/- x/- x/- x/- x/- x/-
Magnesium 18-28 2006-2016
1-2 per year
xx/- xx/- xx/- xx/- xx/- xx/-
Chloride 18-28 2006-2016
1-2 per year
xx/- xx/- xx/- xx/- xx/- xx/-
Sulphate 18-28 2006-2016
1-2 per year
x/- x/- x/- x/- x/- x/-
Other inorganic variables
Fluoride
Boron
Cyanide -/x -/x -/x -/x -/x -/x -/x -/x -/x
Trace elements
Heavy metals 18-28 2006-2016
1-2 per year
-/xx -/xx -/xx -/xx -/xx -/xx
Arsenic & selenium -/xx -/xx -/xx -/xx -/xx -/xx -/xx -/xx -/xx
Organic contaminants
Oil and hydrocarbons 18-28 2006-2016
1-2 per year
-/x -/x -/x -/x -/x -/x
Organic solvents x/- x/- x/- x/- x/- x/- x/- x/- x/-
Phenols x/- x/- x/- x/- x/- x/- x/- x/- x/-
Pesticides xx/- xx/- xx/- xx/- xx/- xx/- xx/- xx/- xx/-
Surfactants x/- x/- x/- x/- x/- x/- x/- x/- x/-
Microbiological indicators
Feacal coliforms
Total coliforms
Pathogens
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Table K.4 shows that currently the DLH-SU data set is the most comprehensive data set of the
three. Only few of the relevant parameters are missing (hardness, conductivity, sodium,
potassium, calcium cyanide, arsenic and selenium, organic solvents, phenols, pesticides,
surfactants), of which for Lake Toba probably only the organic contaminants (solvents, phenols,
pesticides) are of relevance. The PTAN and LIPI data sets are less ‘complete’ with respect to
their set of parameters, as compared to the Chapman guideline.
K.3 Spatial and temporal distribution of data
The spatial vertical distribution of the 3 datasets confirms the different purposes of the data
collection. Both DLH-SU and LIPI aim to cover the whole lake. DLH-SU focusses on parameters
near the shore, probably connected to local pollutant sources and LIPI on characterizing the
lake itself by selecting only mid-lake monitoring points. PTAN is focusing on their aquaculture
farms and has one reference point. For whole lake monitoring on level 2 or 3, the combination
of DLH-SU and LIPI monitoring locations seems a good and non-overlapping match.
As for horizontal distribution (profiles), the DLH-SU data set does not contain depth information,
but a safe assumption would be that samples are taken directly below the water surface, in the
upper epilimnion. Both the LIPI and PTAN data do contain depth profiles; for 100 and 200m
depth, respectively. For the lake assessment, the profile data up to at least 200 m depth are
necessary, especially on temperature and oxygen to fully cover the transition of epilimnion to
the hypolimnion.
The temporal distributions of the data sets vary. PTAN data are most consistent, with monthly
data. DLH-SU monitors 1 to 2 times a year, consistent with their level 1 aim. LIPI data covers
2009 only, though more unpublished data might be present. For level 2 and 3, monthly data
can be regarded as the minimum requirement.99
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L Additional recommendations livestock
L.1 Steps in managing livestock manure
The various costs listed in Table 8.8 for the promotion of biogas production are detailed
below in Table L.1.
Table L.1, Activities proposed for the upscaling of conversion of livestock manure into biogas around Lake
Toba.
step activity category
1 Coordination with kabupaten and other institutions Institutional
2 Assign university to prepare criteria of proposal, design,
evaluation criteria
Information
3 Conduct data collection of livestock owners and numbers of
animals
Information
4 Short course Institutional
5 Site visit and comparative study (high scenario only) Information
6 Development of brochures, information campaign Information
7 Recruit field workers Infrastructure
8 Implementation of pilot biogas plants for smallholders Infrastructure
9 Implementation of pilot biogas plants for big companies Infrastructure
10 Output-based approach for replication Infrastructure
11 Assign university for monitoring and evaluation of the pilot Information
12 Additional training Institutional
L.2 Promotion of biogas production
The promotion of biogas production can be accelerated by various measures. For
instance:
1. Incentives for increased biogas use of solid manure should be created, such as
o Funding for technology development of dry fermentation.
o Funding for technology development of increasing degradation of solid
biomasses via efficient re-treatments.
o Support for co-digestion of slurry and solid manure.
2. Manure-based biogas plants utilising wastes and by-products as co-substrates should
be given priority in subsidy systems and permission processes.
o Energy crops utilisation should be regionally justified so as to avoid harmful
consequences for the environment and competition with food and feed
production.
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3. Manure-based biogas plants with clear plans to optimise the entire manure
management chain before and after the plant should be given priority in subsidy
systems and permission processes.
o Proper solutions for substrate collection, plant design and operation, and
storage, spread and potential post-processing of the digestate require
development to avoid pollution-swapping between different steps.
4. Energy efficient use of the biogas produced should be a key criterion for the
environmental permit and the financial support system.
o The best local utilisation of the biogas energy needs to be determined already
in the planning phase of the biogas plant.
L.3 Sustainable manure management
Additional considerations can be formulated to support Sustainable Manure
Management40: 1. There is an urgent need to raise the awareness of proper manure management. In
particular the possible effects on spreading of livestock diseases to humans, animals.
2. Legislation should be put in place to prevent discharge of animal manure (including
liquids) to surface waters (irrigation and drainage channels, rivers, ponds and lakes).
3. Considering the lack of a sustainable future for livestock production in urban
environments, the development, or continuation, of livestock rearing in the vicinity of
urban areas should be discouraged.
4. Development and adaptation of technologies for effective manure management should
be undertaken, as appropriate for local livestock production systems, and should be
accompanied by the introduction of legislation for effective uptake of technologies.
5. Surveys of current practices of manure application within crop production systems
should be undertaken, and the effects of manure applications on crop yield and soil
quality should be studied. The use of manure as a source of organic matter in poor
and degraded soils should be given attention by farmers, extension personnel and
those persons responsible for land management.
6. Animal manure management lies at the interface between animal production, soil
science and plant production. In order that animal manure is used effectively as a
resource and, therefore, not a source of pollution, there is a need to enhance
cooperation between researchers, legislators and NGOs from these fields. A systems
approach will encourage the integration of animal, soil and plant components, thereby
facilitating effective manure management.
7. An integrated system for the use of organic manure and inorganic fertilizers offers the
greatest potential for the sustainable management of manures while minimizing
40 Adopted from “Guidelines for Sustainable Manure Management in Asian Livestock Production Systems”; IAEA-
TECDOC-1582; May 2008
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environmental pollution and developing confidence amongst farmers in the use of
animal manures.
8. The integrated use of animal manures, in combination with inorganic fertilizers, is likely
to result in increases in crop and forage production, resulting in economic benefit for
farmers, as well as environmental benefits.
9. The development of pilot/demonstration farms (incorporating appropriate levels of
technology) is felt to be an effective way of promoting positive messages on manure
management at the local level.
10. Development of decision support software can assist in manure management system
design and in improved understanding of nutrient fluxes following manure application.
This technology can be very effective in the promotion and uptake of sound manure
management practices.
11. Training courses on nutrient budgets and improved manure management practices
should be designed and an initial test-run conducted for possible wider dissemination.
12. Based on current understanding and experience, a number of information
sheets/pamphlets, on ‘best practices’ of manure management should be prepared and
distributed, for use by extension workers and farmers.
13. The initiation of programs to reward farmers for carrying out sustainable manure
management activities is felt to be a particularly useful strategy. This is believed to be
an effective way of motivating other farmers to adopt ‘best’ manure management
practices.
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M Background information wastewater interventions
This annex provides more details on domestic wastewater (sewage), with special attention
to the tourism industry, as additional background to and elaboration of section 8.4.
M.1 Background and approach
The initial input for the inventory of the existing and planned infrastructure related to
sewage is based on the sanitation strategies (e.g. BPS, SSK, MPS) for each of the
kabupaten in the catchment. These documents have been prepared in most kabupaten in
the framework of the PPSP41 supported by the Urban Sanitation Development Program
(USDP42) and its predecessors. Experience and lessons learned in these programs, as
well as work done by the BWRMP (e.g. as presented in the report Laporan Kualitas, Air
WS Toba Asahan Provinsi Sumatera Utara; TA – BWRMP WISMP 2; October 2015), steer
the identification of interventions and assess issues and developments for successful
implementation (e.g. the comprehensive, multi-faceted program at local level).
In the light of the RPJMN 2015-2019 and as an input for the PPSP-2, USDP prepared an
assessment of the country wide (domestic) wastewater funding and facilities required in
the period of 2015-201943 (and beyond). The database that was developed for this
assessment was adapted (scaled down) to the Lake Toba catchment area and updated
with population figures and developments according to the Sumatra Spatial Model.
In the USDP various interventions are proposed and these serve as a basis for the
proposed investments. The selection of type of WWT facilities is based on the approach
explained in the Buku Referensi (TTPS, 2009). This approach aims to reduce the risk to
health and environment at the lowest costs. Thus, in urban areas with high population
densities and high exposure levels, on-site systems (septic tanks) are no longer preferred
and off-site systems with improved performance (removal efficiencies) are selected, which
is a general applied approach (UNEP, 2004). In Table M.1 the selection criteria are listed
to determine the most suitable type of sanitation facility.
41 The National Accelerated Sanitation Development for Human Settlements Program or Program Nasional
Percepatan Pembangunan Sanitasi Permukiman (PPSP) is a national program launched by the government
of the Republic of Indonesia for the development of integrated sanitation, from national to local level, by
involving all stakeholders from government and non-government parties (http://www.ppsp.info/). 42 The Urban Sanitation Development Program (USDP) is a technical support project, within Accelerated
Sanitation Development for Human Settlements Program or Program Percepatan Pembangunan Sanitasi
Permukiman (PPSP). USDP took a role to facilitate and further strengthen GoI institutions at the national,
provincial and, indirectly, at the local level to be involved in implementing the program. Funded by Embassy of
the Kingdom of the Netherlands, USDP supports over 400 cities and regencies throughout Indonesia with
technical, institutional and health related services (http://www.usdp.or.id/). 43 Sanitation Needs Assessment 2015-2019; USDP, January 2015, USDP-R-PIU.T-10083-2
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Table M.1, Selection criteria for wastewater facilities per type of area features.
BPS
criteria
Residential
pop.density
(pp/ha)
General
description
Type of WWT
system
Examples of
system
Rural < 100 Rural areas On-site systems Septic tank
Rural >100 Peri urban Community based IPAL communal/
MCK
Urban < 25 Very Low density
urban areas
On-site systems Septic tank
Urban 25-100 Low density
urban areas
Existing houses on-
site; New
developments off-
site
Existing: septic
tanks; New
developments:
IPAL Kawasan
Urban 100-250 High density
urban areas
off-site systems IPAL Kawasan
Urban >250 off-site systems IPAL Terpusat
Specific considerations:
• Country wide BPS 2010 data show that in urban areas nearly a quarter (23%) of poor
households practice open defecation (in the non-poor areas this was 7%). Around lake
Toba the reported percentage open defecation lies around 30% (except for Karo:
12%). Many of the areas where urban poor live could qualify for an off-site system.
However, this is not considered the most feasible options. This is because
o off-site systems require a certain amount of water available to transport the
solids, which is not likely to be the case, as often proper water provision is
lacking as well;
o areas are often temporary or concern non-legal houses, and;
o both willingness and availability to pay for operation for this group of
households is very limited44.
For these households, temporary facilities (either MCK or IPAL communal) are a more
appropriate solution. During a general renovation/rehabilitation of such areas, a more
structural solution (e.g. off-site system) can be considered. When putting the 2018-
2042 period in perspective these households are assumed to be connected to off-site
systems.
• In this assessment, an off-site (IPAL Terpusat) system is only proposed if:
o The indicated urban and population density values apply;
o The number of households connected in one Kab/Kota to this system exceed
10,000 (equivalent to 50,000 people);
o the GDP per indicated Kab/Kota reaches a value of 3,000 US$ (based on 2010
BPS value and expectedly 3,500 US$ by 2015), following Bappenas’ findings
on sustainability of large off-site systems in other developing countries;
44 It is, however, a political decision to apply a ‘polluter pays’ principle.
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o In case the two latter conditions are not met, one or more IPAL Kawasans are
proposed instead of an IPAL Terpusat. Possibly these systems could be further
connected in the long-term future.
• Existing urban conditions:
o Many of the urban on-site systems do not comply with the definition of a septic
tank and are more like pit latrines or leach pits (Cubluks) (Kearton et al., 2013).
The result is that there is still a lot of leakage of polluted water to the
groundwater;
o In addition, often the septic tank overflow is connected (together with the
greywater) to the drainage system that eventually discharges to the surface
water (WSP, 2013);
o In both of these situations human health as well as the quality of surface and
groundwater in urban areas are jeopardized.
• The approach to convert from existing systems to future “improved” systems in urban
cases is as follows: In order to improve the urban health and environmental conditions,
the described existing conditions should eventually be minimized. This entails (1) the
removal of poorly performing septic tanks that pollute the ground- and surface water
and connect to a sewerage collection system, and (2) interception and treatment of
the effluent septic tank water and greywater before it reaches the surface water.
o The former activity is to be best performed when renovations in the households
are taking place and requires active campaigning and socialization of the
individual households in line with the development of the sewer
system/interceptor system.
o The second activity, which aims to intercept and treat the water before being
discharged to surface water is best started from a location just before
discharge point and then gradually moving upstream to locations closer to the
house.
o Thus, eventually, part of these households will be connected to off-site
systems (even though they are already counted as “improved”). In this
assessment, it is estimated that in a 20 year time period half (50%) of the
existing urban population currently recorded as having a septic tank/cubluk will
be connected to an off-site system. For the first 5 years (2018-2022) this value
is only 5%.
Septic tanks and community based systems require regular desludging. However,
households in rural areas with low densities (<25 pp/ha) do not require this and IPLT’s will
only serve the households served by a septic tank and community based systems in urban
areas and higher density rural areas. The minimum size of an IPLT is 10,000 people,
whereas the maximum sizes is 200,000 people. If there are more people that require an
IPLT a second one will be constructed.
Applied cost figures:
An analysis was carried out to determine the investment (CAPEX) and operational costs
(OPEX) for wastewater collection and treatment facilities (Figure M.1). A distinction is
made between investment figures for existing and new developing areas. In new to be
developed areas costs for sewer works are expectedly lower and, if planned properly,
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these works can be done in conjunction with the general new area development. In this
assessment, the costs for sewer systems for new areas are expected to be reduced by
50%45 compared to the investments in an existing area. The cost for the wastewater
treatment Plant (WWTP) itself is expected to be the same either way.
Cost figures for off-site systems were updated from the Waste Water Management
Investment Roadmap46 which was drafted for the ADB funded City Wide Sanitation
Investment Program.
Figure M.1, Applied unit rates for indicated wastewater facilities.
Legislation
In theory, there are many regulations and incentives to manage wastewater (see also
section 3.4. For example, the standard on wastewater management is outlined in
Ministerial Regulation of KLHK No. 68/2016. Ministerial Regulation of PUPR No. 4/2017
was issued regarding the implementation of domestic waste water management system.
Until now, the Districts of the area surrounding Lake Toba have a tendency to follow
directives from the Ministry of Home Affairs. However, in the instruction letter from the
Minister of Environment and Forestry that determines the water quality classification of
Toba, the Ministry of Home Affairs was not copied. So far, the Districts have not shown
45 Based on data of the Dutch situation it is found that more than half of the costs of the sewer system in
existing areas are related to the opening and closing of existing roads/pavements. In new
developments, the opening up of the streets is not relevant and the construction of pavement is
considered part of the general development and a 50% factor for sewer system development is applied. 46 City Wide Sanitation Investment Program, Waste Water Management Investment Roadmap; Asian
Development Bank, May 2016; BE1344/R001/MvK/Indo
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any commitment to wastewater collection and treatment. For more information on relevant
legislation, see section 3.4.
M.2 Investment scenarios
For the intermediate scenario C, the intervention type selection is done according to national
guidelines, with 85% Minimum Service Standards and 15% Basic sanitation in 2022 and 100%
Minimum Service Standards in 2042 (Figure M.2). In the high scenario D the level 100%
Minimum Service Standards is reached in 2022, combined with off-site systems for core tourist
areas. Table M.2 shows for each of the scenarios the number of new wastewater systems to
be constructed until 2022 and 2042.
Figure M.2, Indicative development of new wastewater systems in the period 2018-2022 for the intermediate
scenario C.
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Table M.2, New wastewater systems targeted for 2022 and 2042 in the intermediate and high investment
scenarios.
on-site CBS IPLT IPAL Kawasan
Intermediate scenario C
2022 22,845 644 16 15
2042 40,718 1,446 26 31
High scenario D
2022 24,593 276 17 92
2042 33,666 379 25 206
The costs presented in section 8.4 are total costs based on unit cost per person; however, these cost need to be covered from different sources. These budgets need to come from both private and public sources. And the public sources can be subdivided into national and local level as well is by department (i.e public works and ministry of health. Finally, the cost includes hardware (i.e. physical measures) and software (i.e. advocacy/socialization and studies/design). The following table shows how the budget is divided (% allocated) by government level and department.
Table M.3, Budget division by government level and department – Wastewater On-site CBS IPAL Kawasan
Activity div % source* div% source* div% source*
Studies
-Master plan
0.25 N_PU_S
-LARAPAMDAL,FS
0.25 Lo_PU_S
Design
-guidelines
1 N_PU_S 1 N_PU_S
-detailing
4 U_S 3 N_PU_S
Campaign Advocacy, Socialization
-General 5 N_AE_S 2 N_PU_S 0.5 Lo_AE_S
-kabkot 5 Lo_AE_S 4 Lo_AE_S 2 Lo_AE_S
Land acquisition
11 U_La 3 Lo_La
Construction activities
-House connection 9 U_H 24 U_H 13 Lo_PU_H
-Sewer; IPLT for onsite
1 N_PU_H 22 N_PU_H 43 N_PU_H
-Treatment 80 U_H 32 N_PU_H 34 N_PU_H
All 100
100
100
Notes: Level: N=national, Lo=local (Provincial and/or kab/kot), U=user Department: PU = Public works (or construction), AE= Advocacy and Empowerment (=Ministry of health) Type: S= Software; H= Hardware, La=Land
The IPLT and communal system can be financed by the central government providing that
the municipalities have met the “readiness criteria”, e.g. land availability and institutional
set-up. As above mentioned, land availability is a challenging issue (cultural significance).
One solution to reduce the challenge is by developing a regional system where one
infrastructure will serve several municipalities. A regional system is more attractive for the
central government (MPWH) to finance. The institutional issue can be solved by assigning
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PDAM Tirtanadi in Parapat to be responsible for the sludge management and for that
purpose it needs to be supported by a provincial regulation. Table M.4 shows how the budget is divided by government level and department for the base scenario. A large part of the cost (~30%) is allocated to the users/community.
Table M.4, Budget by government level and department in the intermediate scenario C for wastewater.
period Origin of funds WWT IDR
Total 25 years (2018-
2042)
Investments
National 1,779 Billion
Local gov't (Kabkot+Prov) 259 Billion
users/community 1,041 Billion
total 3,079 Billion
OPEX 48,768 Million/y
Total 4 years (2018-
2022)
Investments
National 774 Billion
Local gov't (Kabkot+Prov) 122 Billion
users/community 493 Billion
total 1,389 Billion
OPEX 27,037 Million/y
Total 4 years (2018-
2022)
Investments national division
Infra (Public works) 688 Billion
Design and studies (PU) 20 Billion
CA /instit. (Health +
Bangda)
66 Billion
total 774 Billion
Total 4 years (2018-
2022)
Investments local division (prov/Kabkot)
Infra (Public works) 73 Billion
Design and studies (PU) 1 Billion
CA /instit. (Health +
Bangda)
49 Billion
total 122 Billion
Table M.5 shows how the budget is divided by government level and department for the high scenario D. The total budget is remarkably higher; however, the cost for the users and community is about 40% that of the intermediate scenario. This is the result of the shift from community-based systems to IPAL Kawasan.
Table M.5, Budget by government level and department in the high scenario D for wastewater.
period Origin of funds WWT IDR
Total 25 years (2018-
2042)
Investments
National 6,246 Billion
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Local gov't (Kabkot+Prov) 1,380 Billion
users/community 430 Billion
total 8,056 Billion
OPEX 134,405 Million/y
Total 4 years (2018-
2022)
Investments
National 3,318 Billion
Local gov't (Kabkot+Prov) 733 Billion
users/community 311 Billion
total 4,362 Billion
OPEX 66,900 Million/y
period Division national WWT
Total 4 years (2018-
2022)
Investments (national division)
Infra (Public works) 3,046 Billion
Design and studies (PU) 161 Billion
CA /instit. (Health +
Bangda)
110 Billion
total 3,318 Billion
Total 4 years (2018-
2022)
Investments local division (prov./Kabkot)
Infra (Public works) 625 Billion
Design and studies (PU) 9 Billion
CA /instit. (Health +
Bangda)
99 Billion
total 733 Billion
Supply chains would be different for each of the scenarios. Figure 8.9 shows a potential supply chain for Parapat, and Figure M.3, Figure M.4, and Figure M.5 suggest supply chains for the low B, intermediate C, and high D investment scenarios, respectively.
Figure M.3, Supply chain for low investment scenario B (after Tilley et al. 2008).
User
InterfaceStorage / Primary Treatment
Transportation /
Conveyance
Centralized
TreatmentRecycle / Disposal
Recycled
sludge
Effluent to
river / lake
Ground
water
Public
toiletSeptic Tank (ST)
Sludge
TruckSTP (IPLT)
Infiltration
area
Items
Infrastructure
Finance CSR or Local Government LG / Province Central Gov.
Regulation Set the performance of the public toilet
Local governmentInstitutionEnv agency to
monitorLocal private sector or LG agency
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Figure M.4, Supply chain for intermediate investment scenario C (after Tilley et al. 2008).
Figure M.5, Supply chain for high investment scenario D (after Tilley et al. 2008).
M.3 Parapat
For the concrete suggestion for improvement of the existing sewerage system in Parapat, a separate cost assessment was made. Concrete suggestions for the existing sewerage system in Parapat are: a. Repair the existing sewer line, either fully (best scenario) or at least in the
commercial area (intermediate scenario);
b. Additional sewer line to receive more customer;
c. Improve the process in the existing WWTP. d. Connect effluent of septic tank to the sewer line at a later stage (part of the IPAL
Kawasan system).
e. Design additional IPAL Kawasan
f. Construct additional IPAL Kawasan
User
InterfaceStorage / Primary Treatment
Transportation /
Conveyance
Centralized
TreatmentRecycle / Disposal
Recycled
sludge
Effluent to
river / lake
Ground
water
WC / toilet Septic Tank (ST)Sludge
TruckSTP (IPLT)
Infiltration
area
Items
Infrastructure
Sewer line
1st
stage
2nd
stage
WWTPEffluent to
river / lake
Finance Customer LG / Province Central Gov.
Regulation Standard ST – Connect to sewer
PDAM Tirtanadi to manageInstitutionEnv agency to
monitor
User
InterfaceStorage / Primary Treatment
Transportation /
Conveyance
Centralized
TreatmentRecycle / Disposal
Recycled
sludge
Effluent to
river / lake
WC / Toilet Sewer line WWTP
Items
Infrastructure
Finance CustomerProvince /
Central GovCentral Gov.
Regulation Obligation to connect & fee
PDAM Tirtanadi or Local GovernmentInstitutionEnv agency to
monitor
Customer for house connection
LG for branch sewer
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g. Construct reliable public toilet including the below-structure (septic tank) at tourism
hotspots;
Table M.6, Three investment scenarios for wastewater management at the existing wastewater treatment
plant in Parapat.
Total costs (US$) for Parapat
Low Intermediate High
Infrastructure
a. Repair existing sewer lines in Parapat
150,000 750,000
b. Additional sewer line to receive more customers
2,700,000
c. Improve the process in the wastewater treatment plant
,.000,000
d. Connect effluent of septic tank to the sewer line (at a later stage)
80,.000
e. Construct reliable public toilet including the below-structure (septic tank)
150,000
Institutional
f. Local regulation for customers to connect to sewer
25,000
g. Enforce the hotels and restaurants to connect to sewer
20,000
h. Prepare local regulation to construct septic tank in accordance to technical standard
20,000
i. Assign PDAM Tirtanadi for O&M 5,000
j. Assign responsible institution for the operation of the public toilet
5,000
Information
k. Open contact with private companies
5,000
l. Set the performance of the public toilet
5,000
Total of each scenario (US$) 215,000 950,000 7,470,000
M.4 Institutional recommendations on wastewater management47
47 Largely based on City Wide Sanitation Investment Program (2016).
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M.4.1 General considerations
Sanitation development in the Lake Toba catchment cannot operate in a vacuum.
Implementation of the Wastewater Management Investment Roadmap (City Wide
Sanitation Investment Program, 2016), especially with regards to the further planning and
implementation of physical infrastructure will inevitably need to be aligned with the national
planning and budgeting procedures. National targets will need to be translated in the
planning and budgeting at provincial and local levels and reflected in the strategic planning
of the concerned provincial and local government departments, for which mechanisms are
in place.
Beside planning and budgeting the required infrastructure, which essentially need to be
undertaken at local levels, it is acknowledged that a successful achievement of higher
levels of access to improved waste water management needs to go hand in hand with
(sometimes drastic) policy reforms. In addition, in view of the ambitious targets set,
Government is facing a serious capacity gap, especially in having sufficient skilled and
experiences officials at all levels of government and in all technical and non-technical
agencies required to deal with sanitation development in a professional way and in
planning as well as implementation. This also holds true for the national consultancy
sector. Capacity building and training is a key subject of on-going programs in the
sanitation sector that indeed receives the necessary attention. However, it will take time
before this will bear fruit, for instance in terms of skills development for local administrators
and the availability of newly graduated sanitation engineers able to join government
agencies or consultancy firms.
Local governments need to understand the implications of the targets set by the central
government for their own situation and that ‘business as usual’ in planning and budgeting
for improving sanitation is no longer adequate. It is important that local government officials
are properly advocated and are made aware that they must step up (i) their own financing
for sanitation development, and (ii) get actively engaged in sourcing external funding. The
financing modalities and especially the readiness criteria of such external funding sources
should be fully understood and taken into account in planning and budgeting.
For the higher investments in infrastructure, for which external funding from central and/or
provincial government would be available it is important for local governments to first
comply with the readiness criteria; hence plan and allocate funds for that with priority.
These would typically include (i) Master and Feasibility planning; (ii) Meeting social and
environmental safeguards if co required (impact assessments); (iii) Land acquisition; (iv)
Detailed engineering designs; and (v) Ensuring community awareness and participation.
All this should be undertaken first and budgets allocated accordingly.
M.4.2 Policy actions
Successful sanitation development has to go hand in hand with reform of the sector.
Institutional and procedural related aspects to sanitation development at national and local
level, including legislation and regulatory provisions need to be addressed in concrete
actions. Table M.7 and Table M.8 present an overview of recommended policy actions at
national and local level, respectively. Actions marked with ‘Immediate’ should be
addressed in 6 to 12 months, actions marked with ‘Short-term” in the coming 1 to 2 years.
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Table M.7, Recommended policy actions at national level to support implementation of the Wastewater
Management Investment Roadmap (City Wide Sanitation Investment Program, 2016).
Priority Area Immediate Actions
6 – 12 months
Short-term Actions
1 – 2 years
Strengthen National Regulation, Oversight and Monitoring
Secure a Joint Ministerial Regulation on the effectiveness of programs and activities for development of sanitation and water supply
Outline the establishment of a National Sanitation Development Council charged with coordinating legislation and regulation and overseeing and monitoring performance of local governments
Secure regulation on asset transfer and local sanitation management (post construction)
Outline the establishment of a National Sanitation Management Board charged with coordination of and managing sanitation investments
Secure Bappenas regulation on the management and organization of Nawasis to ensure that it becomes the data source for sector monitoring and fund allocation;
Develop and/or strengthen Sewerage and Septage Management Laws outlining obligations, mandates and implementation arrangements
Balance Investments Develop program(s) for improving on-site sanitation at scale
Include tertiary sewerage and household connection in basic designs, including costing
Allocate resources (financial and human) for faecal sludge management
Develop and implement investment program for medium-scale sewerage systems (IPAL Kawasan, for up to 5,000 hh connections)
Improve Funding Clarify funding source related readiness criteria and build capacity at local government levels to receive funding
Reform and remove legal barriers to subsidizing improved on-site sanitation for low income and disadvantaged households and facilitate practical and affordable mechanisms for financial support
Prioritize and provide funding for measures directly increasing access levels (no regret measures)
Remove regulatory barriers for putting in place cost reflective pricing schemes and sustained tariff collection mechanism
Align national faecal sludge management programs with improving on-site sanitation
Improve Standards Review and develop improved national standards for access to improved waste water management covering the entire service chain (section M.2) and in line with international criteria
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Priority Area Immediate Actions
6 – 12 months
Short-term Actions
1 – 2 years
Intensify inclusion of social aspects
(Re-)develop and promote behaviour change communication packages and strengthen delivery modalities
Restructure Capacity Building and Training
Decentralize responsibilities for operational implementation of CBT
Finance CBT through ministries involved with sanitation development
Engage education and training institutes in developing appropriate course curricula on sanitation planning, implementation and management
Improve Monitoring and Evaluation
Optimize the use of the National Water and Sanitation Information System (Nawasis)
Table M.8, Recommended policy actions at local level to support implementation of the Wastewater
Management Investment Roadmap (City Wide Sanitation Investment Program, 2016).
Priority Area Immediate Actions
6 – 12 months
Short-term Actions
1 – 2 years
Strengthen local regulation
Develop standard template and promulgate Govenor Regulations or Decrees on the position of the provincial Roadmap
Review and develop improved Standard Operation Procedures for wastewater and sludge treatment facilities
Develop standard template and promulgate Mayoral/Regental Regulations or Decrees on the position of the district SSK/MPS as input for local planning
Develop and adapt local regulations for putting in place cost reflective pricing schemes and sustained tariff collection mechanism
Develop standard template and promulgate a Mayoral/Regental Regulation or Decree on the establishment of a wastewater management organisation
Balance Investments Allocate local resources for improving on-site sanitation at scale
Allocate local resources (financial and human) for faecal sludge management
Allocate local resources and implement investment program for medium-scale sewerage systems (IPAL Kawasan, for up to 5,000 hh connections)
Improve Funding Align local funding for faecal sludge management programs with improving on-site sanitation
Establish subsidy schemes for improved on-site sanitation for low
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Priority Area Immediate Actions
6 – 12 months
Short-term Actions
1 – 2 years
income and disadvantaged households
Improve Standards Adhere to national standards but consider local conditions and local regulations
Develop and implement
M.4.3 Technical assistance
Apart from recommended technical assistance (TA) support in the fields of national and local regulations, finding a right balanced investment regime and to improve national codes, standards and permitting modalities for each of the investment packages, or combinations thereof, will require external support in scoping, planning and preparatory studies, and design, tendering and construction supervision of civil works. Technical assistance could be financed directly by the central, provincial, or local governments or through Bilateral Grants, dedicated technical assistance Grants or Loans, or technical assistance provided as part of bigger investment loans of international financing institutions (IFI). Table M.9presents an overview of recommended technical assistance, together with a suggested funding source.
Table M.9, Modalities and funding options for technical assistance in implementation of the Wastewater
Management Investment Roadmap (City Wide Sanitation Investment Program, 2016).
Description of technical assistance Proposed Funding Souce
Timeframe
Strengthen national and local regulations
1.1 Assist national government with the development and establishment of a dedicated National Sanitation Development Council and National Waste Water Management Board
Bilateral Grant Short to medium term
1.2 Review and recommend strengthening or new national legislation
Bilateral Grant Short term
1.3 Develop standard/templates for local regulations and modalities for enforcement
Bilateral Grant Immediate
1.4 Review and recommend improvements on current permitting systems and their enforcement
Bilateral Grant Short term
Balance investments
2.1 Assist LGs developing and establishing faecal sludge management, align this with improved on-site sanitation including the formation of a dedicated waste water management organisation with a practical institutional development trajectory developed and implemented
Bilateral Grant or IFI TA Loan
Immediate
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Description of technical assistance Proposed Funding Souce
Timeframe
2.2 Assist national and local governments establishing a pilot or a broader program for planning and implementing medium-scale sewerage systems (IPAL Kawasan)
Bilateral Grant or IFI TA Loan
Immediate
Improve standards
3.1 Review and recommend improvements to national codes and standards
Bilateral Short term
Improve Implementation
4.1 Review and improve advocacy programs and their dissemination modalities
Bilateral Grant Immediate
4.2 Assist LGs with Master Plan, Feasibility Studies, EIAs, Resettlement, DED, Tendering and Construction Supervision
TA Loan or tied to IFI Loan Programs or Projects
Immediate to short term
Capacity Building and Training
5.1 Design HRM of waste water management organisations
Bilateral Grant or IFI TA Loan
Immediate
5.2 Design a dedicated capacity building program for waste water management organisations
Bilateral Grant or IFI TA Loan
Immediate
Monitoring and Evaluation
6.1 Improve Nawasis and strengthen utilization at provincial and local levels
Bilateral Immediate
To ensure adequate allocations for sanitation development, funding possibilities could be
explored to reallocate funds from other sectors; and increase borrowing from international
financing agencies; and pursue sanitation infrastructure development as a preventive
public health measure. The latter would make it eligible for funding under the 10% budget
earmarked for public health from provincial and local budgets. The sector itself has scope
to further develop cost recovery through charging service fees. At a national level, the
revenue could be increased through introducing new or revised ‘sanitation related’ taxes
or levies.
M.4.4 Other recommendations
Summarizing, planning and coordination between major stakeholders in sanitation
development could be improved by establishing an independent, responsible body at
catchment level to effectively regulate sanitation development, that is also charged with
monitoring performance against minimum service standards. The ‘Urban Waste Water
Framework’ (Figure M.6) can be adapted to the situation in the Lake Toba area. This
framework integrates the various drivers of domestic waste water management into a
comprehensive urban waste water management scheme. Together, the independent body
and the framework can create and maintain an enabling environment that embraces
regulatory conditions in a strong institutional setting.
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Figure M.6, Urban Waste Water Management Framework.
In addition to the issues mentioned above, a “National Law on Sanitation” should be
drafted, approved and promoted. This would facilitate urgent decision making on a number
of legal/regulatory aspects related to sanitation development mentioned in Table M.7 and
Table M.8. At the beginning of the process, institutional roles and responsibilities need to
be clarified, including the establishment of and capacity building for a ‘wastewater
management unit’ in charge of catchment-wide sanitation services; development of all
components of the sanitation service chain (figures in section M.2), followed by the
handover of assets built and managed by different agencies to the agency ultimately in
charge of wastewater management.
Wastewater regulations must be established, promoted and enforced, requiring among
others:
• Existing and new households to connect to sewerage systems, where they exist;
• Households to build improved on-site sanitation in areas without sewerage;
• Institutionalization of facilities for faecal sludge management and mechanisms for
regular emptying of septic tanks;
• Payment of tariffs or contributions to infrastructure construction (improved on-site
sanitation or connection to sewer) or operation (sewerage and/or emptying services).
As part of the promotion and improvement of the balance of investments (Table M.7 and
Table M.8) it is crucial to include smaller infrastructure and faecal sludge management,
acknowledging that more than 90% of wastewater management is on-site and in need of
substantial investments to ensure compliance with environmental standards. In planning,
design and construction, tertiary sewers and household connections must be given equal
emphasis as wastewater mains and treatment facilities. Where tertiary networks and
household connections are not part of the main project funding, then as a minimum
requirement they must be included in the overall system design to optimize it and to better
enable local government to plan and budget for their construction.
A common issue of septic tanks is that these are not always built in accordance with the
technical standard, i.e. not watertight. This contributes to ground water pollution and may
contaminate wells and create health risks. To support the achievement of the sanitation
coverage target, for the last few years the Ministry of Public Works and Housing (MPWH)
c.q. Directorate General of Human Settlements has launched an “output based program”.
Under this program the municipal that provides standard septic tanks to households can
get reimbursed from the central government.
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In the preparation of practical phased sanitation investment plans, the full-service chain
for both on-site and sewerage systems must be addressed (see figures in section M.2).
Adopting a step-wise approach to investment will facilitate efficient spending, matched to
demand. In this respect it is wise to use up and optimize idle capacity of existing off-site
systems and sludge treatment facilities (IPLT) first. Existing sewerage systems and sludge
treatment facilities can be rehabilitated and expanded to more households.
Additional recommendations:
Improve codes and standards and related technical aspects
• Improve minimum service standards for access to improved sanitation, sewerage
and faecal sludge management.
• Ensure national standards cover entire sanitation service chains and can be easily
adopted at a local level.
• Improve national codes and standards for on-site systems, sewer connections,
treatment and reuse.
• Allow for multi-year contracting of facilitators and services providing consultants.
• Improve construction quality, operations and maintenance.
Pay appropriate attention to social aspects
• Develop behaviour change communication packages and institutionalize advocacy
mechanism.
• Inform the public of wastewater standards, targets and responsible agencies so they
understand their rights and increase demand on local governments.
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Focused capacity building
• Accept limited effectiveness and impact of formal training, and shift to coaching
instead.
• Identify subject areas for which sufficient capacity development can only come
through increased numbers of graduates from the regular education system.
• Decentralize responsibility for operational implementation of capacity building and
training.
• Finance capacity building and training from the ministries involved with sanitation
development.
Improve and further institutionalize monitoring and evaluation
• Optimize the use of the National Water and Sanitation Information System (Nawasis)
as decision support system.
• Arrange for institutional embedding of Nawasis.
• Collect and collate information and undertake performance assessments of off-site
and on-site waste water management systems.
• Include monitoring of system performance with the aim to check meeting minimum
service standards and upload performance contracts with utilities into Nawasis.
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N Other sectors
N.1 Solid waste
N.1.1 Approach and background
Currently, the management of solid waste is under Environmental District Services according
to the Government Regulation no.18/2016 (see section 3.4). This is a structural change from
previously operation under City Planning and Sanitation District Services, which has not been
fully implemented yet and is not functioning properly. The district governments have not
established any formal arrangement for waste management and currently there are no formal
final garbage disposal sites (TPA) or areas. Unlike for wastewater, there are no directives for
reaching a certain solid waste coverage target. On a national level (Bappenas) priority is given
to improvement of the urban solid waste situation for the period 2015-2019. No additional
infrastructure is proposed for rural areas. Without such directives given from the Ministry of
Home Affairs to the Districts, there seems to be a reluctance and lack of motivation from the
Districts to implement improvement actions on solid waste treatment.
Solid waste management is one of the basic local government services that need to involve the
communities. It is included in the Sanitation Strategy for Districts and Cities (or SSK) prepared
by the assembled city sanitation working groups (POKJA Sanitasi). The community,
represented by KSM, is responsible for collecting the garbage from the source to the
intermediate collecting point (TPS). From that point to the final disposal site (TPA) should be
under the responsible local government agency. In practice, the local communities use the
‘open dumping method’.
At the moment, solid waste might not contribute much to the water quality degradation of Lake
Toba and therefore the impacts have not been modelled. However, this may be different in the
future with more people. Moreover, lack of good solid waste management is bad for tourism.
As with (domestic) wastewater, the PPSP-2 USDP prepared an assessment of the country wide
solid waste funding and facilities required in the period of 2015-2019 (and beyond) for the
RPJMN 2015-2019. The database that was developed for this assessment was adapted
(scaled down) to the Lake Toba catchment area and updated with population figures and
developments according to the Sumatra Spatial Model. Tourism development has been
accounted for.
For MSW two activities have been distinguished. The first one deals with collection, transfer and transport systems of solid waste and the second one deals with the final treatment or disposal of solid waste. Table N.1 shows the proposed developments as per current policies based on (1) urban and rural features, (2) time of developments and (3) population densities for these activities.
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Table N.1, Planned interventions for MSW.
Type Rural Urban
Implementation Only after 2022 2018-2022 2023-2042
Density (pp/ha) <25 >25 <100 >100 <100 >100
Collection no yes yes yes
Disposal no yes Kab/Kota without
TPA
Build new TPA in
Kab/Kota with
already existing TPA
3R
(50% of people
targeted)
Home
compost
At TPS
(decentral)
level
At TPS
(decentral)
level
Central level
in Kab/Kota
without TPA
At TPS/
community
level
Central level
in Kab/Kota
without TPA
Note:
Because of a low success rate with 3R community based systems operated by the community;
a different operating system (e.g. operated by the dinas kerbersihan) should be considered to
sustain these facilities
Specific considerations for rural areas:
In line with the view of Bappenas, the priority lies on improvement of the urban situation for the
medium term. No additional infrastructure is proposed for rural areas per national policy.
However, in the longer term the higher dense rural population will be served by MSW
infrastructure as well. In this assessment, a rural area is classified as high density when the
residential population is more than 25 pp/ha (based on the expected 2027 situation). Thus, for
all rural areas with lower densities no collection or landfills will be developed in the short and
long term. However, in this assessment promotion of 3R and home composting for these areas
is included after 2022.
Specific considerations for landfills:
In order to identify the investment costs, it is expected that collection is done by motor sampah
and transfer takes place in a TPS-III with containers from where it is transported by Armroll
truck. Waste is finally disposed of in a sanitary landfill. Landfill development follows a stepwise
approach. This means that in the first phase the land for the complete period until 2042 is
purchased. Further, a first cell with a lifetime of 5 years and the facilities are constructed (office,
weighing bridge, vehicles, leachate treatment plant). After the first five years, an extension is
developed, again with a lifetime of 5 years. However, offices and leachate treatment plants only
require some minor upgrading. Thus, the second phase of the landfill development has lower
specific costs than the first development.
Specific considerations for 3R:
In PPSP (2010-2014) 3R (Reduce, Reuse, Recycle) is promoted. 3R includes the recovery and
processing of organic waste into compost and recovery of plastics, paper and other reusable
products like glass, timber, and metals. Data provided by PU shows that by the end of 2013
310 3R community based stations were constructed48. Figure N.1 shows that for rural areas
with residential population densities below 25 pp/ha after 2020 composting at a household level
is promoted. For higher densely rural populated areas, communal composters at the level of a
TPS station are proposed. In all cases, there is direct potential for reuse. Also for lower dense
(<100 pp/ha) populated urban areas communal composters at the TPS level and direct reuse
are proposed. Based on the current experience with communal 3R stations, which show a
48 Data are obtained from RINCIAN per SATKER 2013 provided by the Ministry of Public Works
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rather low (about 30% mentioned only) success rate only, the management of these systems
should be with the a dinas, rather than a community. For the high dense urban areas, a
centralized 3R facility is proposed. Recently larger scale 3R systems are being introduced and
tested, like in Banda Aceh, Bima and Cijantung. These systems consist of a recoverable waste
separation step (plastics and papers), a digestion step and a composting step. The refuse is
finally disposed of in a landfill. In this assessment, a differentiation is made between centralized
3R stations that (1) apply composting only, and (2) that apply digestion followed by
composting49. Plastic and glass recovery is applied in both types of centralized 3R facilities. In
order to come to a 20% waste reduction that is finally disposed in a TPA, the waste of about
30% of the population needs to be processed via 3R.
Figure N.1, Specific investment prices (CAPEX in IDR) per type of area (urban/rural) and management (3R or rural).
The unit running cost figures (OPEX) for the described cases are presented in Figure N.2.
49 Several pilots are currently taking place in Indonesia with this type of treatment system. Advantage of this
approach is that besides the production of compost, also biogas is produced, which, if centrally and in
sufficiently large quantities produced, can act as a source of energy. This however requires higher
investment costs. In this assessment it is assumed that half of the central 3R systems apply digestion and
composting, whereas the other half applies only composting besides the plastic and glass separation.
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Figure N.2, Specific running costs (in IDR) per type of area (urban/rural) and management (3R or rural) – figures in
brackets are revenue.
N.1.1.1 Existing Facilities
Table N.2 shows the existing facilities for solid waste disposal in the 7 kabupaten surrounding Lake
Toba. None of the landfills is designed or constructed as a proper sanitary landfill; all are operated
as open dumping.
Table N.2, Existing facilities for solid waste disposal.
Kabupaten # TPA* Remarks
Tapanuli Utara 0 units
Toba Samosir 2 units TPA at kec. Laguboti: area of 2 ha, operating from 2001
TPA at kec. Ajibata: area of 0.2 ha, operating from 2005
Both are operated as open dumping.
Simalungun
Dairi 1 unit TPA at kec. Berampu: area of 4 ha, operating as open dumping.
Humbang Hasundutan 1 unit TPA Saitnihuta: operating as open dumping.
Samosir 2 units TPA at kec. Simanindo
TPA at kec. Ronggor Nihuta.
Both are operated as open dumping.
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Kabupaten # TPA* Remarks
Karo 3 units 1. Nang Belawan 2. Keriahen 3. Tongging
No special design (just a field with open dumping practice).
* Tempat Pemrosesan Akhir – Solid waste landfill
N.1.2 Investment scenarios
N.1.2.1 Infrastructure
For solid waste two scenarios are considered; an intermediate scenario that follows the national
policy, a low scenario that envisages a more realistic, slower, rate of implementation, and an
accelerated scenario that reaches 100% coverage by 2022. Table 8.12 shows for each of the
scenarios the access to domestic waste collection and disposal or 3R facilities. For the
intermediate scenario, the criteria for the type selection are applied across the Lake Toba area
as envisaged in Figure N.3. For the accelerated scenario, map is presented in Figure N.4.
Figure N.3, Development of solid waste systems in the period 2018-2022 for the intermediate scenario C.
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Figure N.4, Development of solid waste systems in the period 2018-2022 for the high scenario D.
N.1.2.2 Institutional Improvements could be made with commitment from regional leaders, aiming at improving solid waste management to support tourism in Lake Toba. The province could lead the development of a regional waste management program, together with the seven kabupaten draining into the lake. Concrete suggestions for Lake Toba:
a. Contract private sector(s) for transporting the solid waste;
b. Manage the waste sorters working at the TPA
c. Facilitate work for the waste sorters, making it easier to collect recyclable material
at the TPA.
d. Facilitate the community (through PKK) to start “at home composting”
e. Facilitate the community (through PKK) to establish “bank sampah”
One way to attract the attention of the regional leaders is by correlating it with tourism instead of with health.
N.1.2.3 Costed scenarios Table N.3 shows details of the investment required to reach 80% collection/treatment urban – none for rural by 2022 and 100% collection/treatment urban + rural by 2042. Total coverage does not reach 100% because some rural areas do not qualify for collection/disposal even in the long term. Also given is the yearly OPEX required for operation and maintenance of the systems. Note that currently an estimated 0% of population's waste is disposed of in a sanitary landfill; costs are based on prices of TPA sites constructed by 2013
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Table N.3, Solid waste intervention targets and investment cost in the intermediate scenario C (in IDR).
Sub-sector MSW
System IDR Collection
activities
Final disposal and
3R facilities
Total MSW
New Investments (2018-
2042)
Billion 157 869 1,025
targets access to safe
waste disposal
0-4 years (2018-2022) 12% 12% 12%
5-10 years (2023-2027) 92% 94% 92%
11-15 years (2028-2032) 92% 95% 92%
16-25 years (2033-2042) 93% 95% 93%
Investment planning
Inv.: 0-4 y (2018-2022) Billion 8 120 128
Inv.: 5-10 y (2023-2027) Billion 116 460 576
Inv.: 11-15 y (2028-2032) Billion 11 125 136
Inv.: 16-25 y (2033-2042) Billion 22 164 186
OPEX: at 4 y Million/y 14,254 4,139 18,393
OPEX: at 10 y Million/y 102,414 28,379 130,793
OPEX: at 15 y Million/y 110,806 30,717 141,523
OPEX: at 25 y Million/y 127,588 35,393 162,982
Table N.4 shows the investment required to reach 100% collection/treatment urban + rural by 2022 and onward. In this case 100% coverage is reached because the type selection for low density rural areas is overruled. Also given is the yearly OPEX required for operation and maintenance of the systems. Currently an estimated 0% of population's waste is disposed of in a sanitary landfill; costs are based on prices of TPA sites constructed by 2013
Table N.4, Solid waste intervention targets and investment for the high investment scenario D (in IDR).
Sub-sector MSW
System IDR Collection
activities
Final
disposal
and 3R
facilities
Total MSW
New Investments (2018-
2042)
Billion 157 885 1,042
targets access to safe
waste disposal
0-4 years (2018-2022) 100% 100% 100%
5-10 years (2023-2027) 100% 100% 100%
11-15 years (2028-2032) 100% 100% 100%
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Sub-sector MSW
System IDR Collection
activities
Final
disposal
and 3R
facilities
Total MSW
16-25 years (2033-2042) 100% 100% 100%
Investment planning
Inv.: 0-4 y (2018-2022) Billion 113 295 408
Inv.: 5-10 y (2023-2027) Billion 10 156 167
Inv.: 11-15 y (2028-2032) Billion 11 171 182
Inv.: 16-25 y (2033-2042) Billion 22 262 284
OPEX: at 4 y Million/y 94,511 27,151 121,662
OPEX: at 10 y Million/y 102,414 29,548 131,962
OPEX: at 15 y Million/y 110,806 31,944 142,750
OPEX: at 25 y Million/y 127,588 36,737 164,326
The cost presented in the above tables are total costs based on unit cost per person; however, these cost need to be covered from different sources. These budgets need to come from both private and public sources. And the public sources can be subdivided into national/local level as well is by department (i.e public works and ministry of health. Finally, the cost includes hardware (i.e. physical measures) and software (i.e. advocacy/socialization and studies/design). Table N.5 shows how the budget is divided (% allocated) by government level and department. This is elaborated in Table N.6 for the intermediate scenario C and in Table N.7 for the high scenario D. For the summary Table 8.13, the total of mobilized funds in a low investment scenario B serve as reserved funds.
Table N.5, Budget division by government level and department – Solid waste
Activity Collection-transfer-
transport
Treatment
div% source* div% source*
Studies
-Master plan 3 N_PU_S 1.5 N_PU_S
-LARAPAMDAL,FS 1 Lo_PU_S 1 Lo_PU_S
Design
-guidelines 2 N_PU_S 2 N_PU_S
-detailing 2 Lo_PU_S 3 Lo_PU_S
Campaign Advocacy,
Socialization
-General 1 N_AE_S 0.5 N_AE_S
-kabkot 2 Lo_AE_S 1 Lo_AE_S
Land acquisition 10 Lo_La 20 Lo_La
Construction/procurement
activities
53 Lo_PU_H 55 N_PU_H
(civil)
-Collection/Treatment 26 U_H
(collection)
16 Lo_PU_H(
Elec&mec
h)
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All 100
100
Notes: Level: N=national, Lo=local (Provincial and/or kab/kot), U=user Department: PU = Public works (or construction), AE= Advocacy and Empowerment (=Ministry of health) Type: S= Software; H= Hardware, La=Land
Table N.6, Budget by government level and department for the intermediate scenario C on solid waste.
period Origin of funds WWT IDR
Total 25 years (2018-2042) Investments
National 541 Billion
Local gov't (Kabkot+Prov) 445 Billion
users/community 39 Billion
total 1,025 Billion
OPEX 162,982 Million/y
Total 4 years (2018-2022) Investments
National 74 Billion
Local gov't (Kabkot+Prov) 52 Billion
users/community 2 Billion
total 128 Billion
OPEX 18,393 Million/y
Total 4 years (2018-2022) Investments (national division)
Infra (Public works) 67 Billion
Design and studies (PU) 5 Billion
CA /instit. (Health + Bangda) 2 Billion
total 74 Billion
Total 4 years (2018-2022) Investments local division (prov./Kabot)
Infra (Public works) 9 Billion
Design and studies (PU) 40 Billion
CA /instit. (Health + Bangda) 3 Billion
total 52 Billion
Table N.7, Budget by government level and department for the high investment scenario D on solid waste.
period Origin of funds WWT IDR
Total 25 years (2018-2042) Investments
National 551 Billion
Local gov't (Kabkot+Prov) 452 Billion
users/community 39 Billion
total 1,042 Billion
OPEX 164,326 Million/y
Total 4 years (2018-2022) Investments
National 188 Billion
Local gov't (Kabkot+Prov) 192 Billion
users/community 28 Billion
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period Origin of funds WWT IDR
total 408 Billion
OPEX 121,662 Million/y
Total 4 years (2018-2022) Investments national division
Infra (Public works) 165 Billion
Design and studies (PU) 16 Billion
CA /instit. (Health + Bangda) 7 Billion
total 188 Billion
period Division Local (prov./Kabkot) WWT
Total 4 years (2018-2022) Investments local division (prov./Kabot)
Infra (Public works) 81 Billion
Design and studies (PU) 101 Billion
CA /instit. (Health + Bangda) 10 Billion
total 192 Billion
N.1.3 Conclusions and recommendations
• Cost for solid waste management is 12%-30% of wastewater cost (depending on
wastewater type selection);
• Difference in total cost (until 2042) between the national targets (base scenario) higher
targets (accelerated scenario) on Lake Toba catchment is negligible;
• Applying higher targets results in a shift of cost to an earlier period (until 2022);
• Main burden of solid waste management cost lies with local and national government.
Even more so than domestic wastewater, solid waste has a limited direct effect on the water
quality of Lake Toba. However, as with wastewater, aspects such as health, wellbeing and
environmental amenities make it necessary to address proper disposal of solid waste—in
particular in the light of tourism development.
N.2 Erosion reduction
N.2.1 Background
The unsustainable conversion of forests surrounding Lake Toba into other types of land use,
and associated illegal logging and land and forest fires, have led to a decrease in Lake Toba’s
water quality, among others because Toba stream water and surface runoff have stimulated
the growth of algae. While community wastes and waste waters also contribute, the unique
combination of major and minor nutrients, trace elements, and natural organic compounds
released by the erosion of Toba watersheds together stimulate the algal growth. Erosion
control, forest rehabilitation, and better land-use management are therefore critical to maintain
the health of Lake Toba.
Many regulations have been issued by the national and subnational governments over the
years to solve the problems associated with erosion. These regulations are often related to the
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national targets and initiatives on restoration, such as the National Movement for Rehabilitation
(GN-RHL/Gerhan) launched in 2003 and the One Billion Trees program launched in 2011. The
current national target is to rehabilitate up to 5.5 million hectares of ‘critical land’ nationally by
2019. In many of those initiatives, Lake Toba appears on the list of priority areas. The visits of
the President or the Minister of Environment and Forestry to Lake Toba are often accompanied
by ceremonial tree planting and speeches about the importance of rehabilitating the forests
surrounding the lake.
The planning and execution of erosion control and reforestation have mainly been the domain
of the national and sub-national government agencies and implemented in a top-down
approach. As a sign of mistrust, a few weeks after the President and his entourage did a
ceremonial tree planting near the shore of Lake Toba, some villagers uprooted the trees
because those do not belong to the species that the locals wanted to plant in the area. This is
emblematic of the problem with many restoration projects in Indonesia, whereby there is little
sense of ownership by the locals as they are not involved in the decision-making process.
The Save Indonesian Lake Movement (‘Germadan’) in 2009 (see section 3.4) for Lake Toba
attempts to review all the regulations related to Lake Toba and analysed the gaps in the overall
management of Lake Toba, including its surrounding. The Ministry of Environment and
Forestry, together with the Provincial Forest Service, is now implementing a reforestation
program. In this program, members of the community are invited to manage 10 hectares of
forest, for which they get permission to plant 1 hectare with whatever trees they want. The
stakeholders expressed fears that the GERMADAN is at risk of becoming yet another review
or planning document with little impact or no implementation because it does not legally bind
the stakeholders mentioned in the document to conduct certain actions.
Another problem is the potentially contradictory regulations and actions that would work against
the erosion control and reforestation efforts. For example, the edict issued by President Jokowi
to establish a special authority to revive and manage Lake Toba’s tourism industry (PP No.
49/2016) contains a section about re-zoning some areas surrounding the lake currently
classified as “protected forest” into other uses in a fast-tracked process. This fast-track
approach could possibly bypass some due process needed before the legal status of forest
estates can be altered. Further, a weak law enforcement process has let illegal logging to take
place in the forests near Lake Toba, including in protected forest areas. If unchecked, large-
scale illegal logging could greatly undermine the efforts to restore forests in the Toba
landscape.
N.2.2 Investment scenarios Several interventions would reduce erosion in Lake Toba’s catchment area. Below various suggestions are made, some of which would have optimal effects, while others can be considered the bare minimum. In Table 8.14 these are summarised with approximate costs and an indication of total budget for each of the two scenarios.
N.2.2.1 Infrastructure
Healthy forests act as a filter to keep pollution out of water. Strong roots anchor soil against
erosion and material on the forest floor helps absorb nutrients and sediment. But when forests
are disturbed and degraded, sediment flows into streams and pollutes water.
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Natural infrastructure approaches can mitigate and prevent further damage in watersheds.
Establishing conservation zones, engaging in agroforestry and other sustainable forestry
practices and regulating road development can help. Figure N.5 compares the costs of grey
infrastructure with green infrastructure such as watershed conservation, forestation, and
wetlands in the United States. Green infrastructure is less costly than investing in water filtration
plants or improving wastewater treatment plants and systems.
Figure N.5, Investment costs for natural infrastructure and gray infrastructure.
While cost-benefit analyses of restoration and establishing “natural infrastructure” for the
catchment of Lake Toba have not been done yet, several studies on restoration in Indonesia
suggest that the costs to restore degraded landscapes are relatively small (Table N.8). The
cost to restore through the community forestry scheme, which would allow local communities
to develop agroforestry and agro-tourism, appears to be lower than other schemes. Indeed, a
study conducted by World Resources Institute Indonesia and World Agroforestry Center
(ICRAF) in the Musi Watershed of South Sumatra suggests that all restoration interventions,
including agroforestry, rehabilitation, natural regeneration, yield relatively high benefit to cost
ratios and internal rates of return, with agroforestry emerging as the best option economically
(unpublished document).
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Table N.8, Standard costs per hectare for forest rehabilitation and restoration strategies (FAO, 2016).
Strategy Standard costs (US$/ha) Sources
Industrial timber plantation (HTI) and
community-based timber plantation (HTR)
666-12,111 MOF (2009)
Community forestry scheme (HKm) 60 Arlan (2013)
Deposit for mining reclamation 1,500-2,000 Sunandar (2013)
Restoration ecosystem 1,400 Arlan (2013)
In addition to conducting natural restoration, building several simple structures, e.g.
containment dam and gully plugs in the upper watershed, controller dam and terraces in the
central part of the watershed, and infiltration wells in the lower watershed can go a long way in
the effort to reduce erosion. Further, such structures could help prevent natural disasters
(floods and landslides) and protect vital buildings located downstream. Additional analyses will
help determine where and how many of such structures need to be built in the catchment of
Toba so that the costs could be estimated. According to Ministry of Forestry’s guideline on the
rehabilitation program, the unit costs for building structures that could reduce erosion in
Sumatra range from US$ 278 to 17,863 (Table N.9).
Table N.9, Standard costs per unit of physical/grey infrastructures built to reduce erosion (Ministry of Forestry,
2013)
Structure to be built Cost/unit in 2012 (US$)
Containment dam 2,506
Controller dam 17,683
Infiltration well 383
Gully plug 278
Concrete suggestions for Lake Toba:
a. Natural infrastructure: construct and restore nature-based solutions such as forests and
wetlands.
b. Construct grey infrastructure to reduce erosion, such as containment dams, checkers,
gully plugs, and terraces on or around steep slopes.
c. Restore degraded lands in the catchment, taking into account ecological, socio-political,
economic, and cultural aspects, to improve both forest cover and people’s livelihoods.
N.2.2.2 Institutional
The social forestry scheme and customary forest scheme, which are essentially community-
managed forests schemes, could be explored as an alternative of managing the forests around
Lake Toba. In Indonesia’s medium term development plan, the government targeted 2.5 million
hectares of forests allocated for communities each year. The Ministry of Environment and
Forestry has established the Indicative Map of Social Forestry Area (Figure N.6). The task is
now to develop this indicative map into a definitive social forestry area. This scheme could
potentially reduce erosion since it could increase the forest cover in degraded areas or critical
lands, while at the same time the community could receive benefits of forests products from
directly managing the land. The cost per hectare to implement the community forestry scheme
is only about US$ 60, lower than other restoration strategies (Figure N.5 and Table N.9). In
addition to social forestry, the government could consider synchronizing and expanding the
various planting activities that are conducted by private companies around Lake Toba, often as
part of corporate social responsibility schemes.
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In the implementation of these interventions, it is important to pay attention to the business
models for different types of restoration strategies. For example, the agroforestry and agro-
industry that could be developed in Toba will need various on-farm and off-farm support, e.g. a
factory for processing the commodities, or a formal body from the government acting as a
middleman to buy and sell the products, which will help in regulating the price. A feasibility
study conducted by the research center of the Ministry50 does show the benefits of developing
agroforestry in North Sumatra. For example, the net present value/NPV (as of 2013) of coffee
agroforestry was US$ 1,000/ha, while the NPVs for rubber and benzoin agroforestry were US$
787/ha and US$ 434/ha respectively. Differentiating products across districts could also help.
“One Kecamatan One Product” has been introduced in Lebak, Banten in 2001 and could serve
as a lesson learned area. The concept can be translated into “One Kabupaten One Product” in
Lake Toba area. To select the right commodities in certain appropriate locations, academic and
research institutions, such as the Indonesian Tropical Fruits Research Institute (Balai Pelatihan
Tanaman Buah Tropika) under the Ministry of Agriculture can be engaged.
Figure N.6, Indicative area of social forestry around Lake Toba.
To support this, expanding and strengthening agricultural extension services will help the
government in developing agro-industry and agro-tourism near Lake Toba. Technology
transfer, knowledge dissemination, outreach activities to farmers, farmer-to-farmer exchange,
and farmer field schools need to be conducted or organized by government agencies, with
assistance from experienced NGOs. Based on the government’s guideline for extension
services, the monthly operational cost for one extension service staff is ~ US$ 31 (Ministry of
Forestry, 2013). Ideally, there would be one extension service staff per village. One of the
primary goals of such services is to ensure the adoption of sustainable planting processes,
especially for onion and potato, which will help conserve the environment while improving the
agricultural yield and, hopefully, farmers’ income.
50 http://www.worldagroforestry.org/sea/Publications/files/paper/PP0342-14.pdf
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Concrete suggestions for Lake Toba:
d. Introduce and develop agro-industry and agro-tourism with strong community
involvement, encompassing all parts of the value-chain, as part of efforts to improve
people’s livelihoods while reducing the extent of critical/degraded lands.
e. Encourage local communities to adopt best planting practices so as to reduce erosion
and avoid detrimental impacts of fertilizers and business-as-usual planting practices.
f. Strengthen both the regulations and institutional aspects of restoration, especially for
restoration through social forestry/customary forest schemes and partnerships with
private sector (via corporate social responsibility schemes)
N.2.2.3 Information
Monitoring from the National Land Agency (or BPN) and from the Ministry of Agrarian and
Spatial Planning should be made tighter in relation to land conversion (land use change from
protection forest to other use), as referred to Presidential Regulation No. 81/2014. At the
provincial lev
el, the monitoring effort should be synchronized with the provincial spatial plan (RTRW).
Monitoring could also be done by the Ministry of Environment and Forestry that oversees the
forest moratorium policy. The Ministry has launched the “Indicative Map for Forest Moratorium”
to halt granting new licenses for forest concession on primary forests and on peatland. Tight
monitoring on forest concessions inside the Lake Toba Water Catchment Area is therefore
essential to prevent non adherence to the policy on the ground. Further, areas in the realm of
the Lake Toba Tourism Area Management Authority (BOPDT) require further study, such as a
strategic environmental assessment, before any rezoning can be conducted. Close monitoring
on their rezoning activity is also needed.
Global Forest Watch Water (GFW Water) is a free global database and interactive mapping
tool designed to help identify deforestation risks to watersheds and opportunities for natural
infrastructure solutions. The tool can help downstream beneficiaries, financing and
development institutions, civil society and research groups apply natural infrastructure as one
of their strategies to enhance water security and improve watershed management. In South
Sumatra, for example, the provincial government is working on incorporating Global Forest
Watch into the provincial government’s situation room room at a cost of around US$ 50,000
(personal communication). A similar initiative could be set up by the provincial government of
North Sumatra.
Concrete suggestions for Lake Toba:
g. Adapt Global Forest Watch Water for use in North Sumatra.
h. Monitor closely land-use conversion around Lake Toba utilizing the various tools
available to reduce illegal deforestation.
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N.2.2.4 Costed scenarios
Table N.10, Summary of measures for erosion control and total costs of two different scenarios.
Measure Costs
Best
scenario
Minimal
scenario
Infrastructure
i. Natural infrastructure (reforestation) 1,150
US$/ha
x
j. Erosion control structures x
k. Restoration of degraded lands x
Institutional
l. Develop agro-industry and agro-
tourism
x
m. Promote best planting practices 859 US$/ha
n. Strengthen regulations and
institutional aspects
x
Information
o. Adapt GFW Water x
p. Monitor land-use conversion x
N.2.2.5 Impacts
Upstream forests, wetlands, and other “natural infrastructure” play a critical role in the supply
of clean water downstream. They stabilize soil and reduce erosion, regulate water flow to
mitigate floods and droughts, and purify water. In the 2010 Java Water Resources Strategic
Study (JWRSS) by Deltares and Royal Haskoning, the on-site benefits of reforestation and
improved agriculture have been calculated as 4.43 and 1.58 million rupiahs annually per
hectare, respectively. In the case of Lake Toba, it is expected that restoration through various
means will make the area more attractive for tourists, and hence would yield relatively high
benefits.