appendix a wetland status quo report€¦ · client contact ms franci gresse tel: 021 526 9400...

APPENDIX A

WETLAND STATUS QUO REPORT

WORKING FOR WETLANDS

PROVINCE: Gauteng

PROJECT: Gauteng North

Phase 2: Wetland Status Quo Report

DRAFT

Report Reference: Doornrandjies

Wetlands

Page ii

Report Control

Approval

Author signature

Date March 2019 Name Retief Grobler

Title Mr

Document control

Report title Doornrandjies Phase 2: Wetland Status Quo Report

Document ID Doornrandjies Client project number

113223113223113223

Prepared by Mr Retief Grobler

Client Aurecon South Africa (Pty) Ltd

PO Box 494

Cape Town

8000

On behalf of Working for Wetlands Programme (WfWet)

Department of Environmental Affairs: Natural Resource Management

Private Bag X447

0001

Client contact Ms Franci Gresse

Tel: 021 526 9400

WfWet contact Dr Farai Tererai

Tel: 012 399 8970

Rev Date Revision details/status Approver

0 Draft Report

1

Contributors

Report reference

Working for Wetland Programme. 2019. Doornrandjies Wetland 3 Phase 2: Wetland Status Quo Report. Prepared by Imperata Consulting CC as part of the planning phase for the Working for Wetlands Rehabilitation Programme. Report No. 2019

Working for Wetlands Doornrandjies Phase 2 Status Quo Report 2019

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Table of Contents List of Tables ........................................................................................................................................... v

List of Figures ........................................................................................................................................ vii

List of Acronyms ..................................................................................................................................... ix

Glossary of Terms.................................................................................................................................... x

1. OVERVIEW OF WORKING FOR WETLANDS ..................................................................................... 1

1.1 Objectives of Working for Wetlands ....................................................................................... 1

1.2 Relevant legislation, policies and guidelines applicable to the project .................................. 1

1.3 Introduction to project ........................................................................................................... 2

2. METHODOLOGY .............................................................................................................................. 4

2.1 Assessment of wetland functioning and condition ................................................................ 4

2.1.1 Assessment of wetland functioning ................................................................................ 4

2.1.2 Ecological importance and sensitivity ............................................................................. 5

2.1.3 Assessment of wetland condition/integrity .................................................................... 6

2.2 Monitoring and Evaluation ..................................................................................................... 7

2.2.1 Fixed Point Photography/ Site Photographs ................................................................... 7

2.2.2 Wetland Assessments ..................................................................................................... 8

3. STUDY AREA .................................................................................................................................... 8

3.1 Regional context ..................................................................................................................... 8

3.2 Climate .................................................................................................................................... 8

3.3 Vegetation types ..................................................................................................................... 9

3.4 National Freshwater Ecosystem Priority Areas ....................................................................... 9

4. ASSUMPTIONS AND LIMITATIONS .................................................................................................. 9

5. WETLAND DESCRIPTIONS .............................................................................................................. 10

5.1 Wetlands identified for Rehabilitation Assessment ............................................................. 10

5.2 Wetlands A21C-01 and A21C-04 ........................................................................................... 10

5.2.1 Wetland Details ............................................................................................................. 10

5.2.2 Wetland Characteristics ................................................................................................ 14

5.2.3 Benchmark or reference state ...................................................................................... 14

5.3 Wetland A21C-05 .................................................................................................................. 15

5.3.1 Wetland Details ............................................................................................................. 15



5.4 Wetland A21C-08, A21C-10 and A21C-11 ............................................................................. 19

5.4.1 Wetland Details ............................................................................................................. 19


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6. STUDY RESULTS ............................................................................................................................. 25


6.1.1 Wetland ecological functioning .................................................................................... 25

6.1.2 Wetland importance and sensitivity ............................................................................. 26

6.1.3 Wetland ecological integrity assessment ..................................................................... 28

6.2 Wetland A21C-05 .................................................................................................................. 32




6.3 Wetland A21C-08 .................................................................................................................. 36




7. CONCEPT WETLAND REHABILITATION INTERVENTIONS .............................................................. 45


7.1.1 Problems within wetland target areas .......................................................................... 45

7.1.2 Rehabilitation aims and objectives within target areas 1 and 2 ................................... 45

7.1.3 Rehabilitation strategy for all assessed areas ............................................................... 45

7.1.4 Monitoring and evaluation for Wetlands A21C-01 and A21C-04 ................................. 48

7.2 Wetland A21C-05 .................................................................................................................. 49

7.2.1 Problems within wetland target area ........................................................................... 49



7.2.4 Monitoring and evaluation for Wetlands A21C-05 ....................................................... 52

7.3 Wetland A21C-08 .................................................................................................................. 54

7.3.1 Problems within Wetlands A21C-08, A21C-10 and A21C-11 ........................................ 54

7.3.2 Rehabilitation aims and objectives within Wetlands A21C-08, A21C-10 and A21C-11 55


7.3.4 Monitoring and evaluation for Wetlands A21C-08, A21C-10 and A21C-11.................. 59

8. REFERENCES .................................................................................................................................. 62


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List of Tables Table 1.1: Project area descriptions for Quaternary Catchment A21C included in the study................ 2

Table 2.1: Ecosystem services supplied by wetlands (Kotze et al., 2007). ............................................. 5

Table 2.2 Ecological Importance and Sensitivity Classes (DWA, 2013)................................................... 6

Table 2.3: Impact scores and present state categories for describing the integrity of wetlands .......... 7

Table 3.1: The MAP, PET and hydrological sensitivity for Quaternary Catchment A21C (Macfarlane et

al., 2008). ................................................................................................................................................ 8

Table 5.1: Wetlands investigated during the Phase 2 site visit to the Doornrandjies area. ................. 10

Table 5.2: Details for Wetland A21C-01. ............................................................................................... 11


Table 5.4: The inferred reference benchmark state of Wetlands A21C-01 an A21C-04. ..................... 15


Table 5.6: The inferred reference benchmark state of Wetland A21C-05. .......................................... 19

Table 5.7: Details for Wetland A21C-08, which consists of Wetland A21C-08, Wetland A21C-10 and

Wetland A21C-11. ................................................................................................................................. 22



Table 5.10: The inferred reference benchmark state of Wetland A21C-11. ........................................ 25

Table 6.1: Wetland functioning of the target area in Wetland A21C-01, at present and with

rehabilitation......................................................................................................................................... 25


rehabilitation......................................................................................................................................... 26

Table 6.3: Summary of EIS Scores for the target area in Wetland A21C-01 at present and with

rehabilitation......................................................................................................................................... 27


rehabilitation......................................................................................................................................... 27

Table 6.5: Hydrological Impact Scores and PES categories for the target area in Wetland A21C-01 at

present (status quo), with rehabilitation and without rehabilitation. ................................................. 28



Table 6.7: Geomorphological Impact Scores and PES categories for the target area in Wetland A21C-

01 at present (status quo), with rehabilitation and without rehabilitation. ........................................ 29

Table 6.8: Geomorphological Impact Scores and PES categories for the target area in Wetland A21C-

04 at present (status quo), with rehabilitation and without rehabilitation. ........................................ 29

Table 6.9: Vegetation Impact Scores and PES categories for the target area in Wetland A21C-01 at




Table 6.11: Overall impact scores and PES categories for the target area in Wetland A21C-01 at





rehabilitation......................................................................................................................................... 32


rehabilitation......................................................................................................................................... 33


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Table 6.16: Geomorphological Impact Scores and PES categories for the target area in Wetland

A21C-05 at present (status quo), with rehabilitation and without rehabilitation. ............................... 34






rehabilitation......................................................................................................................................... 36


rehabilitation......................................................................................................................................... 37


rehabilitation......................................................................................................................................... 37


rehabilitation......................................................................................................................................... 38


rehabilitation......................................................................................................................................... 39


rehabilitation......................................................................................................................................... 39

























Table 7.1: Summary of the anticipated effect of the proposed rehabilitation on the ecological

integrity of the target area in Wetland A21C-01 at present (status quo), with and without the


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proposed rehabilitation intervention, and with expected changes in wetland hectare equivalents

(Macfarlane et al., 2012). ...................................................................................................................... 47




(Macfarlane et al., 2012). ...................................................................................................................... 47

Table 7.3: Proposed rehabilitation interventions for target areas in Wetlands A21C-01 and A21C-04

(also refer to Figure 7.1). ...................................................................................................................... 48




(Macfarlane et al., 2012). ...................................................................................................................... 51

Table 7.5: Proposed rehabilitation interventions for the target area in Wetlands A21C-05 (also refer

to Figure 7.3). ........................................................................................................................................ 51


integrity of Wetland A21C-08 at present (status quo), with and without the proposed rehabilitation

intervention, and with expected changes in wetland hectare equivalents (Macfarlane et al., 2012). 57







Table 7.9: Proposed rehabilitation interventions for target areas in Wetlands A21C-01 and A21C-04

(also refer to Figure 7.5). ...................................................................................................................... 58

List of Figures

Figure 1.1: Location Map of wetlands assessed for rehabilitation in the Doornrandjies area as part of

the October 2018 Phase 2 survey. .......................................................................................................... 3

Figure 5.1: Wetland A21C-01 and A21C-04 as they appeared in 1961 (notice the extensive presence

of cultivation within both wetlands and their catchments). ................................................................ 12

Figure 5.2: Wetlands A21C-01 and A21C-04 along with their respective wetland target areas and

recorded impacts. ................................................................................................................................. 13

Figure 5.3: Extensive erosion in the target area of Wetland A21C-04. ................................................ 14

Figure 5.4: Wetlands A21C-05, A21C-08, A21C-10 and A21C-11 as they appeared in 1961 (notice the

extensive presence of cultivation within both wetlands and their catchments). The large river visible

west of the wetlands is the Jukskei River. ............................................................................................ 16

Figure 5.5: Wetland A21C-05 along with its target area and recorded impacts, which includes

remnant furrows from historical cultivation. ....................................................................................... 17

Figure 5.6: Example or ridge and furrow cultivation within the target area of Wetland A21C-05. ..... 18

Figure 5.7: Clamany Farm Wetland and its three HGM units, namely A21C-08, A21C-10 and A21C-11

with recorded impacts. The three HGM units are assessed as individual wetlands in their own right

due to their dissimilarity. ...................................................................................................................... 21

Figure 5.8: Illustrates the deeply eroded channel in Wetland A21C-08 (top); an unchannelled valley

bottom reach in Wetland A21C-10 (bottom left) and a failed gabion in Wetland A21C-11. ............... 23


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Figure 7.1: Target areas for rehabilitation in Wetlands A21C-01 and A21C-04 along with the locations

of two proposed rehabilitation interventions, namely A21C-01-210-00 and A21C-04-201-00. .......... 46

Figure 7.2: Monitoring photographs for the target areas in Wetlands A21C-01 and A21C-04. ........... 49

Figure 7.3: Target area for rehabilitation in Wetlands A21C-05 along with the locations of all seven

proposed rehabilitation interventions. ................................................................................................. 50

Figure 7.4: Monitoring photographs for the target area in Wetlands A21C-05. .................................. 54

Figure 7.5: Wetlands A21C-08, A21C-10 and A21C-11 along with the locations of existing and

proposed rehabilitation interventions. ................................................................................................. 56

Figure 7.6: Monitoring photographs for new and existing interventions in Wetlands A21C-08, A21C-

10 and A21C-11. .................................................................................................................................... 61


Page ix

List of Acronyms Acronym Explanation

C-Plan Conservation Plan (typically in the form of a spatial dataset at a provincial level)

DEA Department of Environmental Affairs DWAF Department of Water Affairs and Forestry DWS Department of Water and Sanitation (previously referred to as

the Department of Water Affairs and Forestry) EC Ecological Category EI Ecological Importance EIS Ecological Importance and Sensitivity ES Ecological Sensitivity GDARD Gauteng Department of Agriculture and Ruderal Development HGM unit Hydro-geomorphic unit IHI Index of Habitat Integrity NFEPA National Freshwater Ecosystem Priority Areas PES Present Ecological State WfWet Working for Wetlands WMA Water Management Area


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Glossary of Terms Term Explanation

Catchment A drainage basin or land area with convergent contour lines where water flow starts and accumulate to form a drainage network. Also referred to as a watershed (specifically in the US), but a watershed can also refer to a catchment divide

Catchment divide Divisions between catchments, located on areas with divergent contour lines.

Channelled valley bottom wetland (HGM unit)

A valley bottom wetland with a river channel running through it. Channelled valley bottom wetlands are characterised by their position on valley floors and the absence of characteristic floodplain features. Dominant water inputs to these wetlands are from the river channel flowing through the wetland either as surface flow resulting from flooding or as subsurface flow, and/or from adjacent valley side slopes (as overland flow or interflow), (Ollis et al. 2013).

Depression wetland (HGM unit)

An inland aquatic ecosystem with closed (or near-closed) elevation contours, which increases in depth from the perimeter to a central area of greatest depth, and within which water typically accumulates Dominant water sources are precipitation, groundwater discharge, interflow and diffuse (or concentrated) overland flow. Dominant hydrodynamics are primarily seasonal with resultant vertical fluctuations (Ollis et al., 2013).

Floodplain wetland (HGM unit)

A wetland area within a floodplain Water and sediment input to these wetlands is mainly via overspill from a river channel during flooding. Floodplains consists of gently sloping land adjacent to, and formed by, an alluvial river channel (Ollis et al., 2013).

Headcut An erosion feature that can develop within a channel, at the proximal end of a channel, or on an unchannelled slope. They are the precursors to channel development as headcut migration create or extent channels.

Hillslope seep wetland (HGM unit)

See seep wetland

Hydro-geomorphic

A type of aquatic ecosystem distinguished primarily on the basis of landform (shape and setting), hydrological characteristics (nature of water movement), and hydrodynamics (direction and strength of water movement), (Ollis et al., 2013).

Hydromorphic soil Soils with features that have developed under anaerobic conditions due to a fluctuating water table or longer periods of saturation

Hydrophyte Plant species that are adapted to wetter areas and can therefore grow in water or soils that are at least periodically saturated and/or inundated. Can also refer to facultative and obligate hydrophyte species to help indicate the gradient of wetness to which a particular species is adapted.

Instream habitat Includes the physical structure of a watercourse and the associated vegetation in relation to the bed of the watercourse (National Water Act, Act No. 36 of 1998), (NWA)


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Term Explanation

Pan wetland See depression wetland. Riparian habitat/zone/area

The physical structure and associated vegetation of the areas associated with a watercourse which are commonly characterized by alluvial soils, and which are inundated or flooded to an extent and with a frequency sufficient to support vegetation of species with a composition and physical structure distinct from those of adjacent land areas (NWA).

River A linear landform with clearly discernible bed and banks, which permanently or periodically carries a concentrated flow of water. A river includes both the active channel and the riparian zone (Ollis et al., 2013)

Seep wetland (HGM unit)

Wetland area located on gently to steeply sloping land and dominated by the colluvial (i.e. gravity-driven), unidirectional movement of water and material down-slope. Seeps are often located on the side-slopes of a valley, but they do not typically, extend unto a valley floor. Water inputs are primarily via subsurface flows from an up-slope direction.

Unchannelled valley bottom wetland (HGM unit)

A valley bottom wetland without a river channel running through it. These wetlands are characterised by the location on valley floors, an absence of distinct channel banks, and the prevalence of diffuse flows. Water inputs are typically from an upstream channel and seepage from adjacent valley side slopes, if present.

Watercourse Watercourse definitions as provided in the NWA:

• A river or spring; • A natural channel in which water flows regularly or intermittently; • A wetland, lake or dam into which, or from which, water flows

and • Any collection of water which the Minister may, by notice in the

Gazette, declare to be a watercourse. A reference to a watercourse includes, where relevant, its bed and banks.

Wetland Land which is transitional between terrestrial and aquatic systems where the water table is usually at or near the surface, or the land is periodically covered with shallow water, and which land in normal circumstances supports or would support vegetation typically adapted to life in saturated soil (NWA).

Wetland flat (HGM unit)

A level or near-level wetland area that is not fed by water from a river channel, and which is typically situated on a plain or bench. Closed elevation contours are not evident around the edge of a wetland flat. They are characterised by the dominance of vertical water movements associated with precipitation, groundwater inflow, infiltration and evaporation. Horizontal water movements within these wetlands, if present, are multi-directional, due to the lack of any significant change in gradient within the wetland (Ollis et al., 2013).


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1. OVERVIEW OF WORKING FOR WETLANDS Working for Wetlands (WfWet) is a government programme managed under the Natural Resource Management Programme (NRM) of the Department of Environmental Affairs (DEA). It is a joint initiative with the Departments of Water and Sanitation (DWS), and Agriculture, Forestry and Fisheries (DAFF). In this way the programme is an expression of the overlapping wetland-related mandates of the three parent departments, and besides giving effect to a range of policy objectives, it also honours South Africa’s commitments under several international agreements, especially the Ramsar Convention on Wetlands The programme is mandated to protect pristine wetlands, promote their wise-use and rehabilitate those that are degraded throughout South Africa, with an emphasis on complying with the principles of the Expanded Public Works Programme (EPWP) and using only local Small, Medium and Microenterprises (SMMEs). The EPWP seeks to draw significant numbers of unemployed people into the productive sector of the economy, gaining skills while they work and increasing their capacity to earn an income.

1.1 Objectives of Working for Wetlands WfWet engages with provinces, especially government departments and agencies responsible for biodiversity and environment, and municipalities through individual projects. A stronger working relationship with these spheres of government is being promoted through the programme’s emphasis on partnerships. In particular, compatibility with Integrated Development Plans (IDPs) and rehabilitation project objectives will be a key area of future focus. WfWet encourages municipalities to participate in provincial wetland forums because they are the platform for the roll-out of all the programmes processes, including planning for future work. Provincial forums also offer support from the government departments and private sectors that are represented. Partnerships with non-governmental organizations and the private sector are also critical, requiring collaboration and cooperation with a wider range of stakeholders and role players in the wetland management field. The newly identified strategic framework of WfWet has underlined the need for a more refined process that the programme is embarking on with catchment-scale planning. Catchment-scale planning seeks to promote ecosystem-scale outcomes, long-term custodianship, and embedding of rehabilitation in broader local institutions and frameworks. The recent move to a systematic wetland rehabilitation planning process has provided a fertile and conducive platform for partnerships to be formed and/or strengthened as it draws in a much wider stakeholder base. This is in line with NRM’s objective to increase its footprint through Land User Incentive based projects.

1.2 Relevant legislation, policies and guidelines applicable to the project WfWet operates within the context of the Constitution (1996), whereby everyone has the right to an environment that is not harmful to their health and wellbeing, and that is protected. The following national legislation, amongst others, are thus applicable:

• National Environmental Management Act, 1998 (NEMA) • National Environmental Management: Biodiversity Act, No 10 of 2004 (NEMBA) • National Water Act, 1998 (NWA) • Conservation of Agricultural Resources Act, 1993 (CARA) • National Heritage Resources Act, 1999 (Act 25)


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This legislation both directs WfWet in its vision and objectives and regulates the wetland rehabilitation activities which WfWet carries out. WfWet has put in place systems to achieve compliance with all applicable legislation. For example, Basic Assessments for Environmental Authorisation are carried out for all listed activities involved in wetland rehabilitation to comply with NEMA and a Memorandum of Agreement is in place with DWS to ensure compliance with the water licensing requirements of the NWA.

1.3 Introduction to project This wetland status quo report forms part of Phase 2 of the Gauteng North wetland rehabilitation project, which is classified as a Category 2 wetland rehabilitation project. This involves projects where rehabilitation planning is being undertaken in recently prioritized wetlands that are combined with maintenance work in surrounding wetlands present in the area (e.g. Quaternary Catchment A21C). Wetland rehabilitation assessments have been undertaken in the Doornrandjies area, located in the south-western section of the City of Tshwane Metropolitan Municipality (CTMM) and the northern section of the City of Johannesburg (COJ) Metropolitan Municipality. Extensive rehabilitation work has been undertaken by WfWets in the Doornrandjies area over the last ten years. The planned rehabilitation strategy for 2018/2019 will be focussed on six wetland areas, all located within Quaternary Catchment A21C (Table 1.1 and Figure 1.1) Table 1.1: Project area descriptions for Quaternary Catchment A21C included in the study.

Province Gauteng

Quaternary Catchment A21C

Project Name Gauteng North

Land Owner / Partnership Private land

Planning Phase Phase 2

Nearest Town Centurion

Previous Work

Previous rehabilitation work has been undertaken in the area by WfWets. Wetland

with existing rehabilitation interventions include A21C-01, A21C-02, A21C-03 and A21C-

08

Project Description Category 2


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Figure 1.1: Location Map of wetlands assessed for rehabilitation in the Doornrandjies area as part of the October 2018 Phase 2 survey.


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2. METHODOLOGY The rehabilitation of freshwater ecosystems is considered to be a complex undertaking and the planning process involves multiple disciplines. The relevant components of the following methodology were adopted for the project and comprised of multiple steps.

2.1 Assessment of wetland functioning and condition Determining the impacts on the wetland habitat requires the assessment and thus understanding of the levels of functioning and condition/integrity of the wetlands for the current and post-rehabilitation scenarios. Wetlands and other types of watercourses, such as headwater ephemeral channels, were delineated through a desktop approach with little emphasis on the identification and recording of watercourse indicators used for delineation purposes. Emphasis was placed on recording indicators associated with the ecological integrity (health) of watercourses watercourse. Suspected problem area in watercourses that may be suitable for rehabilitation were first identified through a desktop approach and investigated on site during the Phase 2 survey on 30 October 2018.

2.1.1 Assessment of wetland functioning To quantify the level of functioning of the wetland systems, and to highlight their relative importance in providing ecosystem benefits and services at a landscape level, a WET-EcoServices (Kotze et al., 2007) assessment was performed for the current and post-rehabilitation scenarios for all the high priority wetland systems identified during the WfWet Phase 1 planning phase. The WET-EcoServices assessment technique focuses on assessing the extent to which a benefit is being supplied by the wetland habitat, based on both:

• The opportunity for the wetland to provide the benefits; and

• The effectiveness of the particular wetland in providing the benefit. Ecosystem services, which include direct and indirect benefits to society and the surrounding landscape, were assessed by rating various characteristics of the wetland and its surrounding catchment, based on the following scale:

• Low (0);

• Moderately Low (1);

• Intermediate (2);

• Moderately High (3); and

• High (4) The scores obtained from these ratings for the wetland systems were then incorporated into WET-EcoServices scores for each of the fifteen ecosystem services (Table 2.1). The same method was used to assess wetlands and ephemeral channels, collectively referred to as watercourses. This was done for the sake of consistency with other similar assessments being undertaken for WfWets across South Africa In addition, non-wetland ephemeral channels are


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expected to provide similar functions as marginal-temporary wetlands in a semi-arid area, such as the study area. Table 2.1: Ecosystem services supplied by wetlands (Kotze et al., 2007).

Eco

syste

m s

erv

ices s

up

plied

by w

etl

an

ds

Ind

irect

ben

efi

ts

Reg

ula

tin

g a

nd

su

pp

ort

ing

ben

efi

ts

Flood attenuation The spreading out and slowing down of floodwaters in the wetland, thereby reducing the severity of floods downstream

Stream flow regulation Sustaining stream flow during low flow periods

Wat

er q

ualit

y en

hanc

emen

t be

nefit

s

Sediment trapping The trapping and retention in the wetland of sediment carried by runoff waters

Phosphate assimilation

Removal by the wetland of phosphates carried by runoff waters

Nitrate assimilation Removal by the wetland of nitrates carried by runoff waters

Toxicant assimilation Removal by the wetland of toxicants (e.g. metals, biocides and salts) carried by runoff waters

Erosion control Controlling of erosion at the wetland site, principally through the protection provided by vegetation

Carbon storage The trapping of carbon by the wetland, principally as soil organic matter

Dir

ect

ben

efi

ts

Biodiversity maintenance Through the provision of habitat and maintenance of natural process by the wetland, a contribution is made to maintaining biodiversity

Pro

vis

ion

ing

ben

efi

ts

Provision of water for human use

The provision of water extracted directly from the wetland for domestic, agricultural or other purposes

Provision of harvestable resources

The provision of natural resources from the wetland, including livestock grazing, craft plants, fish, etc.

Provision of cultivated foods The provision of areas in the wetland favourable for the cultivation of foods

Cu

ltu

ral b

en

efi

ts

Cultural heritage Places of special cultural significance in the wetland, e.g. for baptism or gathering of culturally significant plants

Tourism and recreation Sites of value for tourism and recreation in the wetland, often associated with scenic beauty and abundant birdlife

Education and research Sites of value in the wetland for education or research

2.1.2 Ecological importance and sensitivity In accordance with DWAF (1999), the ecological importance of a water resource provides an expression of its importance to the maintenance of ecological diversity and functioning at local and wider scales. As WET-EcoServices does not provide a consolidated score that can be used as a target, the assessment scores were incorporated into the Ecological Importance and Sensitivity (EIS) assessment framework to provide an EIS score based on scores for ecological importance and sensitivity, hydro-functional importance, and direct human benefits (DWA, 2013). Table 2.2 provides an overview of the ratings used to interpret the derived EIS


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scores. The same method was used to assess wetlands and ephemeral channels, collectively referred to as watercourses. Ephemeral channels and marginal-temporary wetlands in a semi-arid area, such as the study area, are expected to provide similar functions and have similar sensitivities. Table 2.2 Ecological Importance and Sensitivity Classes (DWA, 2013).

Ecological Importance and Sensitivity Categories Range of EIS

Score EIS

Class

Very high: Wetlands that are considered ecologically important and sensitive on a national or even international level. The biodiversity of these systems is usually very sensitive to flow and habitat modifications. They play a major role in moderating the quantity and quality of water of major rivers.

4 A

High: Wetlands that are considered to be ecologically important and sensitive. The biodiversity of these systems may be sensitive to flow and habitat modifications. They play a role in moderating the quality and quantity of water in major rivers.

>3 and <4 B

Moderate: Wetlands that are considered to be ecologically important and sensitive on a provincial or local scale. The biodiversity of these systems is not usually sensitive to flow and habitat modifications. They play a small role in moderating the quantity and quality of water of major river.

>2 and </=3 C

Low/Marginal: Wetlands that are not ecologically important and sensitive at any scale. The biodiversity of these systems is ubiquitous and not sensitive to flow and habitat modifications. They play an insignificant role in moderating the quantity and quality of water of major rivers.

>1 and </=2 D

None: Wetlands that are rarely sensitive to changes in water quality/hydrological regime. 0 E

2.1.3 Assessment of wetland condition/integrity To determine the level of ecological integrity, a WET-Health (MacFarlane et al., 2007) assessment was performed for the current, post-rehabilitation and without rehabilitation scenarios for the wetland systems (where appropriate). The WET-Health assessment technique gives an indication of the deviation of the system from the wetlands’ natural reference condition for the following biophysical drivers:

• Hydrology - defined as the distribution and movement of water through a wetland and its soils;

• Geomorphology - defined as the distribution and retention patterns of sediment within the wetland; and

• Vegetation - defined as the vegetation structural and compositional state. The impacts on the wetlands, determined by features of the wetlands and their catchments, were scored based on the impact scores and then represented as Present State Categories (PES) as outlined in WET-Health (Table 2.3). The wetland catchment was estimated based on interpretation of terrain topography and 1:50000 topographical maps (


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Table 2.3: Impact scores and present state categories for describing the integrity of wetlands

(MacFarlane et al., 2007).

Impact

Category Description

Impact

Score Range

(0-10)

Present

State

Category

None Unmodified, natural. 0-0.9 A

Small Largely natural with few modifications. A slight change in ecosystem processes is discernible and a small loss of natural habitats and biota may have taken place.

1-1.9 B

Moderate Moderately modified. A moderate change in ecosystem processes and loss of natural habitats has taken place but the natural habitat remains predominantly intact.

2-3.9 C

Large Largely modified. A large change in ecosystem processes and loss of natural habitat and biota has occurred. 4-5.9 D

Serious The change in ecosystem processes and loss of natural habitat and biota is great but some remaining natural habitat features are still recognizable.

6-7.9 E

Critical Modifications have reached a critical level and the ecosystem processes have been modified completely with an almost complete loss of natural habitat and biota.

8-10 F

The scores for hydrology, geomorphology and vegetation were simplified into a composite impact score, using the predetermined ratio of 3:2:2 (MacFarlane et al., 2007) respectively for the three components. The composite impact score was used to derive a health score that then provided the basis for the calculation of hectare equivalents (also referred to as functional area), which can be described as the health of a wetland expressed as an area (Kotze and Ellery 2009). Wetland rehabilitation and maintenance planning.

2.2 Monitoring and Evaluation The monitoring and evaluation of the wetlands relies on collecting relevant baseline information, with the collected data including fixed point photographs. Furthermore, it should include the summary of the systems to be rehabilitated, including:

• number of wetlands to be rehabilitated; • number of HGM units to be rehabilitated; • hectare equivalents gained/secured due to the rehabilitation; and • area (hectares) influenced by the proposed rehabilitation activities (only applicable to

wetland watercourses).

2.2.1 Fixed Point Photography/ Site Photographs Pre-implementation photographs were recorded for the wetland and/or wetland complex, as outlined in WET-RehabEvaluate (Cowden and Kotze, 2009), to provide a visual baseline of the system prior to the implementation of the proposed rehabilitation activities. Visual monitoring can then be undertaken in subsequent years to document the changes of the systems.


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2.2.2 Wetland Assessments The ecological integrity and functioning of the wetlands should be monitored using the WET-Health (Macfarlane et al., 2007) and WET-EcoServices (Kotze et al., 2007) assessment techniques. The assessments undertaken for the Phase 2 planning will form the baseline data of the systems from which future assessments of the systems can be based.

3. STUDY AREA The following section provides an overview of the study area, focusing on the regional context, climate, and vegetation types.

3.1 Regional context The entire site forms part of Crocodile (West) and Marico Water Management Area (WMA), of which Quaternary Catchment A21C forms part of. The latter is associated with a Largely modified (class D) Present Ecological State (PES) and a Moderate Ecological Importance and Sensitivity (EIS) category (Middleton & Bailey, 2008). All of the assessed wetlands are located within the Rhenosterspruit Conservancy. Wetlands in the quaternary catchment are impacted by current and historical cultivation, unregulated grazing and development in the form of small holdings, farm dams, road networks, and sand mining. Another important impact that affect some wetlands within the quaternary catchment is the release of treated sewage effluent from one of the largest sewage treatment facilities in the City of Johannesburg, namely the Northern Waste Water Treatment Works, located in Diepsloot. Treated effluent is released through irrigation in Northern Farm, which flow into wetlands that are connected with the Jukskei River. Treated effluent flowing into wetlands are expected to be rich in nitrogen and phosphate associated compounds, while the hydrology of receiving wetlands are modified by larger flow volumes and velocities. Taking into consideration the above-mentioned degradation of wetland ecosystems, ecosystem rehabilitation is viewed as a means of maintaining the current levels of ecosystem service delivery, and where possible, enhancing the systems’ ability to supply these benefits and services.

3.2 Climate This section provides an overview of the climate within the Quaternary Catchment A21C. An understanding of the climate, i.e. the sensitivity of catchments to hydrological impacts influences rehabilitation planning activities. The hydrological vulnerability factor of wetlands within the quaternary catchment is moderate, with a vulnerability factor of 1.0, based on a mean annual precipitation of 682 mm and a mean annual evaporation of approximately 1700 mm (Macfarlane et al., 2008; Middleton & Bailey 2008), (Table 3.1). Frost is common during winter and rainfall occurs primarily as thundershowers during the summer months (Mucina and Rutherford, 2006). Table 3.1: The MAP, PET and hydrological sensitivity for Quaternary Catchment A21C (Macfarlane et al., 2008).

Quaternary catchment

MAP (mm) PET (mm) Hydrological sensitivity

A21C 682 1700 Moderately


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3.3 Vegetation types Under natural conditions the surrounding landscape and study site would have been characterised by particular vegetation types. The Mesic Highveld Bioregion forms part of the entire study area, while each of the six assessed wetlands overlap with the Egoli Granite Grassland vegetation unit (Mucina & Rutherford, 2006). The Egoli Grassland vegetation unit is a listed Threatened Ecosystem area according to the 2011 Schedule (Government Gazette of December 2011) of the National Environmental Biodiversity Act (Act 10 of 2004), with an Endangered status (Gm 10). All of the wetlands overlap with conservation biodiversity areas (CBA) that are either classified as Irreplaceable or Important, in the provincial C-Plan 3 spatial dataset (version 3.3 published by GDARD). Important Area and Irreplaceable Area sections are associated with confirmed Red Listed plant, bird and/or mammal species, or with habitat suitable for them, or the presence of primary vegetation (GDARD, 2011).

3.4 National Freshwater Ecosystem Priority Areas The National Freshwater Ecosystem Priority Areas (NFEPA) is a tool developed to assist in the conservation and sustainable use of South Africa’s freshwater ecosystems, including rivers, wetlands and estuaries. Noe of the delineated wetland areas overlaps with any wetland area indicated on the 2011 NFEPA wetlands spatial dataset (Nel et al., 2011).

4. ASSUMPTIONS AND LIMITATIONS It is important to note that this assessment was undertaken in a short period of time, with limited field verification. There are therefore a number of limitations to this assessment as outlined below:

• Wetland boundaries are estimated primarily through a desktop approach that made used of time series aerial imagery, including a georeferenced aerial photograph from 1961. A limited amount of time was spent on verifying watercourse boundaries during the site visit. No soil auguring was undertaken but exposed soil profiles, such as channel banks, were inspected where present.

• The wetland catchment area was also delineated through an on-screen digitising desktop approach based on the interpretation of available 5 m contour lines; no GIS modelling was undertaken based on digital elevation models (DEMs).

• Assessment of impacts and rehabilitation outcomes is informed by a structured process but is based to a large extend on a qualitative rather than a quantitative approach. The latter is associated with the collection of more detailed information related to the hydrology, geomorphology and vegetation components of investigated wetlands.

• Wetland surveys are timed to overlap with the dry season in Gauteng Province, which enables a better identification of erosion, sedimentation and drainage impacts, but restricts the collection of vegetation and floristic data in surveyed watercourses.

• It follows that the vegetation component does not inform the PES assessments as accurately as it would have during a wet season survey.

• The level of confidence in the accuracy of the assessed Ecological Importance and Sensitivity (EIS) of each wetland is also reduced by dry season surveys, as the identification of plant species of conservation concern (sensu Raimondo et al., 2009) is restricted during the dry season.


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• Limited time was available for wetland indicator analyses, while the timing of the survey occurred at the end of the dry season when hydrophyte (wetland plant) indicators are still in a dormant phase and not easily identifiable.

• Decisions regarding the suitability for rehabilitation at a specific impact are made on site based on an evaluation by the wetland specialist, engineer and provincial coordinator. Wetland and watercourse assessments are only undertaken afterwards in an attempt to quantify what the contribution of the proposed rehabilitation will be for the targeted watercourse area.

5. WETLAND DESCRIPTIONS 5.1 Wetlands identified for Rehabilitation Assessment Only surveyed wetland sections are assessed in terms of their ecological condition, functioning and sensitivity. This is done as the proposed rehabilitation strategy presented in this report will not necessarily improve and/or stabilise (protect) the entire delineated wetland. In some instances, such as wetlands A21C-01, A21C-04 and A21C-05, only a portion of each wetland will be improved/stabilised through the proposed rehabilitation strategy. These rehabilitation-associated wetland sections are referred to as target areas. Interflow and perched aquifers are expected based on experience of similar wetland systems located within the Halfway House granitic dome. Seepage is therefore an important driver of wetland systems within the Egoli Granite Grassland vegetation unit. Table 5.1: Wetlands investigated during the Phase 2 site visit to the Doornrandjies area.

Wetland Number

Name Watercourse type

Hydro-geomorphic unit

Surface area of delineated watercourse

A21C-01 Doornrandjies 1 Wetland Seep and unchannelled valley bottom wetland 32.3 ha

A21C-04 Doornrandjies 4 Wetland Channelled valley bottom 5.31 ha

A21C-05 Doornrandjies 5 Wetland Seep 14.5 ha

A21C-08 Clamany Farm Wetland Channelled valley bottom 6.76 ha

A21C-10 Clamany Farm Wetland Unchannelled valley bottom 2.59 ha

A21C-11 Clamany Farm Wetland Channelled valley bottom 1.21 ha

5.2 Wetlands A21C-01 and A21C-04 5.2.1 Wetland Details Wetlands A21C-01 and A21C-04 are both located in a first order drainage line positions, with Wetland A21C-04 forming a confluence with Wetland A21C-01 (Figures 1.1 and 5.1). Only two small target areas are assessed in both wetlands (Table 5.2; Figure 5.2). Wetland A21C-04 is very different from Wetland A21C-01, as it contains a deeply eroded channel, while the latter is unchannelled (Figure 5.2). Wetland A21C-04 is regarded as a channelled valley


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bottom wetland, with the channel primarily restricted to the target area (Figure 5.2). Historically the entire wetland existed as an unchannelled valley bottom HGM unit, as is evident from the aerial photograph of 1961 (Figure 5.1). The target area in Wetland A21C-01 is regarded as separate HGM unit that is better represented as a seep than an unchannelled valley bottom wetland (Figure 5.2). This is due in part to the smaller size of the target area and the fact that the target area overlaps with a separate HGM unit that as delineated by Grobler (2008). The transition from a seep to an unchannelled valley bottom wetland is not distinct and some ambiguity remains regarding the most accurate classification of the HGM unit. Table 5.2: Details for Wetland A21C-01.

Wetland Name Doornrandjies 1

Wetland Number/Label A21C-01

GPS Location 25°52'34.64"S 27°58'13.90"E

Catchment Land Use Grassland (most dominant), followed by Urban smallholding and Woodland/Open bush

Catchment Size of Wetland 398 ha

Catchment Size of Wetland Target Area 44.9 ha

Wetland Type (HGM unit) Seep (upstream margin of a larger unchannelled valley bottom HGM). Only the seep is assessed as it overlaps

with the target area

Wetland Land Use Grassland used for grazing (historically cultivated)

Wetland Size 32.3 ha

Target Area 1 Size 3.17 ha

Table 5.3: Details for Wetland A21C-04.



GPS Location 25°52'53.53"S 27°57'44.74"E

Catchment Land Use Grassland (most dominant), followed by Urban smallholding and Woodland/Open bush

Catchment Size of Wetland 86.7 ha

Catchment Size of Wetland Target Area 65 ha

Wetland Type (HGM unit) Channelled valley bottom (previously existed as an unchannelled valley bottom based on aerial

photograph from 1961)





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Figure 5.1: Wetland A21C-01 and A21C-04 as they appeared in 1961 (notice the extensive presence of cultivation within both wetlands and their catchments).


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Figure 5.2: Wetlands A21C-01 and A21C-04 along with their respective wetland target areas and recorded impacts.


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5.2.2 Wetland Characteristics Large portions of both wetlands were cultivated in the past as is evident on the aerial photograph from 1961. The majority of Wetland A21C-04 was previously cultivated, which in addition to the presence of erosion prone soils, are expected to have contributed to the development of an extensive erosion gully within the target area (Figures 5.2 and 5.3). The exposed soil profile in eroded areas appear to represent prismacutanic horizons with rounded “heads” visible at the top of the surface. It is therefore likely that soils within the wetland consisted of duplex soils, with an overlying E-horizon and/or Orthic A-horizon. The target area in Wetland A21C-04 currently function more like an ephemeral channel than a wetland due to the loss of functioning caused by erosion. Large parts of the target area in Wetland A21C-01 were also historically cultivated, but no distinct remnant gullies were identified. Recorded impacts in Wetland A21C-01 include a vehicle crossing and a headcut at the downstream edge of the target area.

Figure 5.3: Extensive erosion in the target area of Wetland A21C-04.

5.2.3 Benchmark or reference state The inferred reference state of Wetlands A21C-01 and A21C-04 are described in Table 5.4. The Present Ecological State (PES) assessments would compared current changes to these expected natural wetland properties.


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Table 5.4: The inferred reference benchmark state of Wetlands A21C-01 an A21C-04.

Characteristic Description

HGM Unit Seep HGM unit located at one of the points of origin of a larger unchannelled valley bottom wetland (Figure 5.2). Also referred to as a valley head seep in some literature.

Wetness Regime and hydrology

Temporary and seasonal/permanent wetness zones were historically present and continue to be present in the target area of Wetland A21C-01. Only temporary and seasonal wetness zones are expected to have been present in the target area of Wetland A21C-04.

No natural channel was present in the reference condition of either wetland and water flow was diffuse across the width of the wetlands. The largest contributor of water is expected to be interflow (subsurface seepage). Sandy soils with a high hydrological conductivity are a common feature of wetlands and surrounding terrestrial areas in the landscape, which is also supported by the number of sand mines in the area. These soils are well-suited to support interflow into wetlands. Perched aquifers that develop on aquitards in the form of underground ferricrete horizons that feed water into wetlands are also a common feature in wetlands associated with the Halfway House Granitic Dome (Batchelor et al., 2009). Hydrological catchment impacts were similar to the present day situation, with minimal transformations visible.

Geomorphology Erosion feature were generally absent from the seep (Wetland A21C-01), while erosion is not expected to have existed in Wetland A21C-04 either. The latter existed as an unchannelled valley bottom wetland on erosion-prone duplex soils before it became channelled due to anthropogenic impacts associated with cultivation and grazing.

It must be stated that not all erosion features are regarded as negative impacts caused by anthropogenic actions, as channel development does occur naturally in headwater settings depending on factors such as the slope, soils, vegetation cover, runoff, rainfall intensity and other parameters. The presence of erosion-prone duplex soils alone may also have resulted in natural channel development. Evidence of extensive grazing and cultivation within Wetland A21C-04, approximately 75 % of the target area was ploughed, are expected to have accelerated erosion. Uncertainty, however, still exists regarding to what extent present day erosion features can be explained by natural or anthropogenic processes or both. The absence of channels in the present day and the absence of channels in 1961 (based on an interpretation of an aerial photograph), suggest that no channel was present in the reference benchmark state of the target areas of both wetlands.

Vegetation Invasive alien plant species, as well as ruderal and agestral weeds were absent in the wetland historically. Ruderal and agestral weeds refers to alien species associated with agriculture and similar disturbances. Alien species would have become established after introduction by settlers of European descent and opportunities created by disturbances, such as cultivation.

5.3 Wetland A21C-05 5.3.1 Wetland Details Wetland A21C-05 is located in a first order drainage line positions and forms a tributary of the Jukskei River (Figures 5.4 and 5.5). It is a seep wetland with a size of 14.5 ha, while the target area that is assessed as part of the rehabilitation strategy is 10.4 ha (Table 5.5; Figure 5.2).


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Figure 5.4: Wetlands A21C-05, A21C-08, A21C-10 and A21C-11 as they appeared in 1961 (notice the extensive presence of cultivation within both wetlands and their catchments). The large river visible west of the wetlands is the Jukskei River.


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Figure 5.5: Wetland A21C-05 along with its target area and recorded impacts, which includes remnant furrows from historical cultivation.


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Table 5.5: Details for Wetland A21C-05.



GPS Location 25°54'14.16"S 27°57'55.69"E

Catchment Land Use Grassland (most dominant) and Urban smallholding

Catchment Size of Wetland 82.7 ha

Catchment Size of Wetland Target Area 72.5 ha

Wetland Type (HGM unit) Seep




5.3.2 Wetland Characteristics Large portions of both wetlands were cultivated in the past as is evident on the aerial photograph from 1961 and remnant furrows associated ridge and furrow cultivation practices that are also common in other wetlands within the Doornrandjies area, (Grobler, 2017). Headcut erosion features have formed in some of the furrows, while the furrows cause a surrounding desiccation effect (Figure 5.5). Dumping has occurred in furrows located close to the vehicle crossing through the wetland target area. The topsoil is sandy with suspected Orthic A-horizons underlain by E-Horizons, while B-horizons associated with illuviation are expected in the lower reaches of the wetland. The vegetation is expected to be secondary due to cultivation impact, by grass species were still recovering after the dry season and recent fire event, which restricted species identification in most instances. The hydrophyte, Imperata cylindrica, does occur in wetter portions of the wetland, such as furrows, and was already in flower. The pioneer shrub, Seriphium plumosum, is common in the wetland. Its encroachment is expected to have been aided by wetland desiccation and a high grazing pressure. Raised ridges have created drier conditions that enabled trees, such as Searsia lancea and S. pyroides, to become established in the wetland. Bare patches with little to no vegetation are also common within the wetland but will decrease during the wet season.

Figure 5.6: Example or ridge and furrow cultivation within the target area of Wetland A21C-05.


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5.3.3 Benchmark or reference state The inferred reference state of Wetland A21C-05 is described in Tables 5.6. The Present Ecological State (PES) assessments would compared current changes to these expected natural wetland properties. Table 5.6: The inferred reference benchmark state of Wetland A21C-05.


HGM Unit Seep HGM unit located in a headwater drainage line position.


Temporary and seasonal/permanent wetness zones were historically present. The extensive ridge and furrow cultivation system is expected to have been required to enable cultivation in a wetland with-well developed seasonal and permanent wetness zones. The slope of the wetland and sandy soils allowed drainage through the ridge and furrow systems.

No natural channel was present in the reference condition of the wetland and linear erosion features currently present are associated with historical cultivation practices. Surface flow in the wetland was therefore diffuse as is common in seep systems.

The largest contributor of water is expected to be interflow (subsurface seepage). Sandy soils with a high hydrological conductivity are a common feature of wetlands and surrounding terrestrial areas in the landscape, which is also supported by the number of sand mines in the area. These soils are well-suited to support interflow into wetlands. Perched aquifers that develop on aquitards in the form of underground ferricrete horizons that feed water into wetlands are also a common feature in wetlands associated with the Halfway House Granitic Dome (Batchelor et al., 2009). Hydrological catchment impacts were similar to the present day situation, with minimal transformations visible.

Geomorphology Erosion features were generally absent within the seep (Wetland A21C-05). Present day erosion features, including eroded furrows and headcuts, are all expected to have developed as a result of anthropogenic activities in the form of ridge and furrow cultivation practices. Natural erosion is expected to have been absent or limited to a few small headcuts that were stabilised by vegetation.

Vegetation Invasive alien plant species, as well as ruderal and agestral weeds were absent in the wetland historically. Ruderal and agestral weeds refers to alien species associated with agriculture and similar disturbances. Alien species would have become established after introduction by settlers of European descent and opportunities created by disturbances, such as cultivation. The wetland was densely vegetated during summer and lacked bare areas.

5.4 Wetland A21C-08, A21C-10 and A21C-11 5.4.1 Wetland Details Wetland A21C-08 was divided into three separate HGM units by Grobler (2008) due to them forming a confluence on the same property (Clamany Farm). Each HGM unit is, however, very different from one another and can be assessed as separate wetlands in their own right. Clamany Farm Wetland can therefore be divided into Wetland A21C-08, A21C-10 and A21C-11 (Figures 5.4 and 5.7). Wetland A21C-08 is a channelled valley bottom HGM unit of 6.76 ha, Wetland A21C-10 is an unchannelled valley bottom HGM unit of 2.59 ha and Wetland A21C-11 is a channelled valley bottom wetland of 1.21 ha (Figure 5.7; Table 5.7). There are no


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separate target areas in any of these wetlands as they are assessed in their entirety as part of the rehabilitation strategy.


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Figure 5.7: Clamany Farm Wetland and its three HGM units, namely A21C-08, A21C-10 and A21C-11 with recorded impacts. The three HGM units are assessed as individual wetlands in their own right due to their dissimilarity.


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Table 5.7: Details for Wetland A21C-08, which consists of Wetland A21C-08, Wetland A21C-10 and Wetland A21C-11.

Wetland Name Clamany Wetland

Wetland Number/Label A21C-08, divided into Wetland A21C-08, Wetland A21C-10 and Wetland A21C-11

GPS Locations 25°54'33.28"S 27°57'18.39"E (Wetland A21C-08)

25°54'41.84"S 27°57'30.24"E (Wetland A21C-10)

25°54'43.17"S 27°57'13.15"E (Wetland A21C-11)

Catchment Land Use (Wetland A21C-08) Grassland, central pivot irrigation, dams, sand mine, informal settlement, Eucalyptus sp. plantation, urban

smallholding

Catchment Size of Wetland A21C-08 1340 ha

Catchment Size of Wetland A21C-10 92.6 ha

Catchment Size of Wetland A21C-11 12.8 ha

Wetland Land Use (Wetland A21C-08) Grassland used for grazing (historically cultivated) and Woodland/Open bush (Wetland A21C-08)

HGM unit Type: Wetland A21C-08 Channelled valley bottom

HGM unit Type: Wetland A21C-10 Unchannelled valley bottom

HGM unit Type: Wetland A21C-11 Channelled valley bottom

Wetland Size: Wetland A21C-08 6.76 ha



5.4.2 Wetland Characteristics Large portions of all three wetlands were cultivated in the past as is evident on the aerial photograph from 1961 (Figure 5.4). Wetland A21C-08 is severely eroded up to bedrock in the channel bed, with a channel depth deeper than 5 m in areas (Figures 5.7 and 5.8). This was not always the case as an interpretation of the aerial photograph from 1961 indicates that the wetland had a poorly developed and non-incised channel less than 60 years ago (Figure 5.4). The hydrology of the wetland has been drastically modified as a result of high volumes of treated sewage effluent being released daily into Wetland A21C-08. This wetland receives the bulk of treated effluent runoff as the majority of watercourses that receive effluent irrigation water flow into Wetland A21C-08 (Figure 1.1). Wetland functioning and ecological integrity have therefore been permanently modified as quantified in Section 6. The current characteristics of the watercourse is closer to that of a perennial river than a wetland, with both indigenous and alien riparian species present on the channel banks of the watercourse. Aliens include Morus alba, Melia azedarach, Populus xcanescens, Salix babylonica and Solanum mauritianum, while indigenous species include Acacia karroo, Asparagus laricinus, Searsia lancea and S. pyroides. Several lateral headcut erosion features were recorded along the left-hand bank of Wetland A21C-08 (Figure 5.7). Wetland A21C-10 is an unchannelled valley bottom wetland that is significantly wetter compared to its pre-disturbance benchmark state (reference condition). The increased wetness is also associated with treated sewage water effluent that is irrigated in its catchment. The volume of effluent that flows into Wetland A21C-10 is lower compared to Wetland A21C-08 due to the smaller size of its catchment and with less irrigation (Table 5.7). The valley


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bottom wetland remains largely unchannelled and only contains headcut erosion features at its downstream reach, at the confluence with Wetland A21C-08 (Figures 5.7 and 5.8). Wetland ecological integrity and functioning is more intact compared to Wetland A21C-08, but many facultative hydrophytes have been replaced with obligate hydrophytes due to the increased wetness in the wetland. A constant inflow of treated sewage effluent water also results in an influx of nitrogen and phosphate nutrients that are normally limited in natural freshwater systems. Alien plant species are able to make use of this abundance of nutrient more effectively than may indigenous hydrophyte species, resulting in the encroachment of alien species, such as the grasses Pennisetum clandestinum and Paspalum dilatatum. Other alien species present in the wetland include Cirsium vulgare, Nasturtium officinale, Oenothera rosea, Trifolium sp., Verbena bonariensis and Xanthium strumarium. Indigenous hydrophyte species include the grasses Eragrostis plana, Imperata cylindrica and Hyparrhenia hirta, the forbs Berkheya radula and Berula erecta, and the sedges Cyperus sexangularis and Schoenoplectus cf. corymbosus. An eroded berm is present in the upstream reach of the wetland and have resulted in the development of a short, yet stable and well vegetated channel. A short, but deep, channel section is also present at the downstream end of the wetland. Wetland A21C-11 is a channelled valley bottom that forms a tributary of Wetland A21C-08 (Figure 5.7). Only a temporary wetness zone is present in the wetland, while the majority of the wetland was historically cultivated (Figure 5.4). No channel appears visible in the wetland in a 1961 historical aerial photograph (Figure 5.4). The wetland is therefore expected to have existed previously as an unchannelled valley bottom wetland that became channelled as a result of cultivation activities and the creation of a vehicle crossing through the wetland (Figure 5.7). A headcut at the downstream end of the wetland was targeted for rehabilitation intervention in 2008 (Grobler, 2008), but the implemented gabion structure failed at an unknown date and needs to be rectified as discussed in Section 7 (Figure 5.8).

Figure 5.8: Illustrates the deeply eroded channel in Wetland A21C-08 (top); an unchannelled valley bottom reach in Wetland A21C-10 (bottom left) and a failed gabion in Wetland A21C-11.


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5.4.3 Benchmark or reference state The inferred reference state of Wetlands A21C-08, A21C-10 and A21C-11 are described in Tables 5.8 to 5.10. The Present Ecological State (PES) assessments would compared current changes to these expected natural wetland properties. Table 5.8: The inferred reference benchmark state of Wetland A21C-08.


HGM Unit Channelled valley bottom HGM unit (weakly channelled and not-incised)


Temporary and seasonal/permanent wetness zones were historically present. Flows were regularly spread out across the valley floor of the wetland. Diffuse flow occurred outside the channel through dense wetland vegetation following bankfull flow events that exceeded the capacity of the channel. Interflow (seepage) into the wetland is expected to have formed an important hydrological driver, both to the HGM unit and to upstream wetland habitat.

Geomorphology Erosion features were restricted to the development of a shallow channel, which may not have been continuous throughout the length of the wetland. No large in-channel or lateral headcut erosion features are expected in the reference condition of the wetland.


Table 5.9: The inferred reference benchmark state of Wetland A21C-10.


HGM Unit Unchannelled valley bottom wetland (same as the present situation)


Temporary, seasonal and potentially permanent wetness zones were historically present. Seasonal and permanent wetness zones were, however, smaller compared to the present day situation as the wetland received less water inflow (no daily release of treated sewage effluent was present in the upstream catchment). Flows were regularly spread out across the valley floor and were diffuse. Interflow (seepage) into the wetland is expected to have formed an important hydrological driver, both to the HGM unit and to upstream wetland habitat.

Geomorphology Erosion features are expected to have been absent within the unchannelled valley bottom wetland.



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Table 5.10: The inferred reference benchmark state of Wetland A21C-11.


HGM Unit Unchannelled valley bottom wetland (differs from the present situation)


Only a temporary wetness zones is expected to have been historically present, but small and localised areas of seasonal wetness may also have existed. This is similar to the present day situation. Flows were regularly spread out across the valley floor and were diffuse. Interflow (seepage) into the wetland is expected to have formed an important hydrological driver.

Geomorphology Erosion features are expected to have been absent within the unchannelled valley bottom wetland and the present day channel is expected to have formed as a result of cultivation practices and the construction of a vehicle crossing that created a flow barrier.


6. STUDY RESULTS 6.1 Wetlands A21C-01 and A21C-04 6.1.1 Wetland ecological functioning Tables 6.1 and 6.2 indicate expected ecosystem-services currently performed by each target areas in Wetland A21C-01 and A21C-04 at the time of the site survey (October 2018), as well as expected changes to ecosystem services that could potentially occur should the proposed rehabilitation strategy be successfully implemented. Ecosystem service improvements are not expected in Wetland A21C-01, as only stabilisation of a single headcut is required (Table 6.1). The proposed stabilisation of the headcut will, however, decrease erosion within the wetland, which will result increase erosion control (Table 6.1). Wetland habitat will be improved in Wetland A21C-04 as sediment trapping will be facilitated within an erosion gully network (Section 7). The most noticeable expected improvements associated with sediment trapping, erosion control and carbon storage (Table 6.2)/ Table 6.1: Wetland functioning of the target area in Wetland A21C-01, at present and with rehabilitation.

Ecosystem Service Current State Post-rehab

Importance Score Percentage Change

Reg

ula

tory

an

d

Su

pp

ort

ing

Serv

ices

Flood Attenuation 1.7 No change

Stream Flow Regulation 2.5 No change

Sediment Trapping 2.3 No change

Phosphate Trapping 2.4 No change

Nitrate Removal 3.0 No change


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Toxicant Removal 2.5 No change

Erosion Control 2.4 10 %

Carbon Storage 1.7 No change

Biodiversity Maintenance 2.9 No change

Pro

vis

ion

ing

Serv

ices

Water Supply 0.9 No change

Harvestable Natural Resources 0.6 No change

Cultivated Foods 0.2 No change

Cu

ltu

ral

Serv

ices

Socio-Cultural Significance 0.0 No change

Tourism and Recreation 1.3 No change

Education and Research 1.8 No change

Table 6.2: Wetland functioning of the target area in Wetland A21C-04, at present and with rehabilitation.



Reg

ula

tory

an

d S

up

po

rtin

g

Serv

ices

Flood Attenuation 1.6 10.3 %

Stream Flow Regulation 2.2 7.7 %

Sediment Trapping 2.0 42.6 %

Phosphate Trapping 1.6 43.9 %

Nitrate Removal 1.9 27.0 %

Toxicant Removal 1.6 41.9 %

Erosion Control 1.6 47.4 %

Carbon Storage 0.3 200.0 %

Biodiversity Maintenance 2.6 9.8 %

Pro

vis

ion

ing

Serv

ices

Water Supply 0.5 36.8 %



Cu

ltu

ral

Serv

ices



Education and Research 0.5 100.0 %

6.1.2 Wetland importance and sensitivity The scoring assessments for these three aspects of ecological importance and sensitivity have been based on the requirements of the National Water Act, Act No. 36 of 1998 (NWA), the


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original Ecological Importance and Sensitivity (EIS) assessments developed for riverine assessments (DWAF, 1999), and the work conducted by Kotze et al. (2005) on the assessment of wetland functions (the WET-EcoServices tool). The Ecological Importance and Sensitivity (EIS) of the assessed target areas in Wetland A21C-01 and A21C-04 are both Moderate (Class C) (Tables 2.2, 6.3 and 6.4). This is partially due to the fact that the wetlands and their target areas are located within a Threatened Ecosystem (Egoli Granite Grassland) and conservation priority areas (based on C-Plan version 3.3). Little information is available regarding the confirmed presence or absence of Species of Conservation Concern within each wetland (sensu Raimondo et al., 2009), as the wetland surveys were undertaken during the end of the dry season when plant species are in a dormant stage and not readily visible. Fauna species are also less active during the dry season and may not be present within the site as they are still away on winter migration (e.g. numerous bird species). The overall level of confidence for the EIS component is therefore low. The EIS category is not expected to change from the current scenario to a future post-rehabilitation scenario (Tables 6.3 and 6.4). The overall Importance and Sensitivity category for each of the wetland target areas decrease with the consideration of Hydro-functional Importance and Direct Human Benefits for the current and post-rehabilitation scenarios (Tables 6.3 and 6.4). The wetlands and their catchments are located within the Rhenosterspruit Conservancy with minimal present day cultivation impacts, direct uses or pollution sources. It is therefore to be expected that hydrological and direct human benefits score low. The proposed rehabilitation strategy will maintain the current Hydro-functional Importance score and class in the target area of Wetland A21C-01 (Table 6.3) The Hydro-functional Importance will improve from a Low/Marginal class to a Moderate class with rehabilitation in the target area of Wetland A21C-04 (Tables 2.2 and 6.4). Direct Human Benefits remain at the same score and in the same class for all scenarios and target areas, with and without rehabilitation (Tables 6.3 and 6.4). The combined, or overall Importance and Sensitivity categories, remain the same for both wetland target areas irrespective of rehabilitation (Tables 6.3 and 6.4). Table 6.3: Summary of EIS Scores for the target area in Wetland A21C-01 at present and with rehabilitation.

Current Post-rehab

Ecological Importance and Sensitivity (EIS) 3.0 3.0

Hydro-functional Importance 2.3 2.3

Direct Human Benefits 0.8 0.8

Overall Importance and Sensitivity Score 2.0 2.0

Overall Importance and Sensitivity Category D D

Table 6.4: Summary of EIS Scores for the target area in Wetland A21C-04 at present and with rehabilitation.

Current Post-rehab

Ecological Importance and Sensitivity (EIS) 2.8 2.8




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6.1.3 Wetland ecological integrity assessment The ecological integrity or Present Ecological State (PES) of the target areas in Wetlands A21C-01 and A21C-01 were assessed based on perceived modifications to wetland hydrology, geomorphology and vegetation. These components of the ecological integrity of the wetland were assessed for the current, post-rehabilitation and without rehabilitation scenarios. Impacts affecting the hydrology, geomorphology and vegetation of assessed wetland areas have already been described in Section 5.2.2. Assessment results that quantify the magnitude of change between the reference condition (Section 5.2.3) and the present condition, as well as the reference condition and the post-rehabilitation condition, are summarised for each wetland health component in Tables 6.5 to 6.11, while the combined results are provide in Table 6.12 for each target area. Each wetland target areas was assessed separately. Hydrology assessment

No change in the combined hydrological impact score or class is expected in Wetland A21C-01 in the event of rehabilitating the target area in its current state (Table 6.5). Failure to undertake rehabilitation can result in the migration of the existing headcut erosion feature through the length of the wetland target area, resulting in the channelisation of the entire target area. This can reduce the current hydrology PES class from a B to a C (Table 6.5). Rehabilitation intervention in Wetland A21C-04 will reduce the combined hydrological impact score from 3.6 to 2.3, but the combined hydrological PES will remain in class C (Table 6.6). Failure to undertake rehabilitation can result in the expansion of the gully network throughout the entire target area, which will reduce the current hydrology PES class from a C to an E (Table 6.6). Table 6.5: Hydrological Impact Scores and PES categories for the target area in Wetland A21C-01 at present (status quo), with rehabilitation and without rehabilitation.

Status quo With rehabilitation

Without rehabilitation

Impact Type Impact Score Impact Score Impact Score

Changes in water inputs 0.0 0.0 0.0

Changes in water distribution and retention patterns

1.6 1.6 3.2

Combined Hydrology Impact Score

1.0 1.0 3.0

PES Category B B C


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Table 6.6: Hydrological Impact Scores and PES categories for the target area in Wetland A21C-04 at present (status quo), with rehabilitation and without rehabilitation.






0.0 0.0 0.0


3.0 3.0 6.5

PES Category C C E

Geomorphological assessment

No change in the geomorphological impact score or class is expected in Wetland A21C-01, in the event of rehabilitating the target area in its current state (Table 6.7). Failure to undertake rehabilitation can result in the migration of the existing headcut erosion feature through the length of the wetland target area, which will reduce the current geomorphological PES class from a B to an E (Table 6.7). Rehabilitation intervention in Wetland A21C-04 will reduce the combined geomorphological impact score from 7.2 to 2.4, while the combined geomorphological PES class will improve from an E to a C (Table 6.8). Failure to undertake rehabilitation can result in the expansion of the gully network throughout the entire target area, which will reduce the current geomorphological PES class from an E to an F (Table 6.8). Table 6.7: Geomorphological Impact Scores and PES categories for the target area in Wetland A21C-01 at present (status quo), with rehabilitation and without rehabilitation.




Erosion features 0.1 0.1 6.4

Depositional features 0.3 0.3 0.3

Combined Impact Score 0.4 0.4 6.7

PES Category A A E

Table 6.8: Geomorphological Impact Scores and PES categories for the target area in Wetland A21C-04 at present (status quo), with rehabilitation and without rehabilitation.





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PES Category E C F

Assessment of vegetation impacts

No change in the vegetation impact score or class is expected in Wetland A21C-01, in the event of rehabilitating the target area in its current state (Table 6.9). Failure to undertake rehabilitation can result in the decrease of the current vegetation PES class from a C to a D (Table 6.9). Alien species can make use of disturbances caused by the advancement of an existing headcut to encroach into the target area. Rehabilitation intervention in Wetland A21C-04 will reduce the combined vegetation impact score from 4.5 to 3.1, while the combined geomorphological PES class will improve from a D to a C (Table 6.10). Failure to undertake rehabilitation can result in the expansion of the gully network throughout the entire target area, which will reduce the current vegetation PES class from a D to an E (Table 6.10). Erosion-associated soil disturbances provide opportunities for the establishment and eventual encroachment of alien plant species. Table 6.9: Vegetation Impact Scores and PES categories for the target area in Wetland A21C-01 at present (status quo), with rehabilitation and without rehabilitation.



Disturbance Class Impact Score Impact Score Impact Score

Old cultivated land 2.25 2.25 1.65

Road crossing 0.25 0.25 0.25

Fire break 0.15 0.15 0.15

Erosion gully - - 2

Remainder 0.15 0.15 0.1

Overall weighted impact score 2.8 2.8 4.2

PES Category C C D

Table 6.10: Vegetation Impact Scores and PES categories for the target area in Wetland A21C-04 at present (status quo), with rehabilitation and without rehabilitation.




Old cultivated lands 0.6 0.6 0.3

Erosion gully 3.6 2.25 5.6

Remainder 0.25 0.25 0.15



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PES Category D C E

Assessment of overall impacts and ecological integrity

For ease of interpretation the scores for hydrology, geomorphology and vegetation are simplified into a composite impact score for each target area in Wetlands A21C-01 and A21C-04, by weighting the scores obtained as outlined by Macfarlane et al. (2007). The combined PES class for the target area in Wetland A21C-01 remains stable with rehabilitation but can decrease by two categories to a class E in the event of no rehabilitation (Table 6.11). This decrease is related to the potential advancement of an existing headcut erosion feature with related impacts to the hydrology, geomorphology and vegetation wetland PES components. This assessment assumes the worse possible impact, in terms of headcut advancement. There are several unknown factors that can naturally halt headcut advancement within the target area, while the headcut may also remain stable at its current position for many years (see Section 7 for further details). The combined PES class for the target area in Wetland A21C-04 improves by one category from a class D to a class C with rehabilitation (Table 6.12). This improvement is related to effective sedimentation and rewetting within the gully system in the target area of Wetland A21C-04. It is expected that the overall PES class of the target area in Wetland A21C-04 can decrease by one category, from a class D to a class E in the event of no rehabilitation (Table 6.12). This is dependent on the expansion of the existing gully network within the wetland target area. Table 6.11: Overall impact scores and PES categories for the target area in Wetland A21C-01 at present (status quo), with rehabilitation and without rehabilitation.

Current (Status quo)

Post Rehab Without rehab

Hydrology 1.0 1.0 3.0

Geomorphology 0.4 0.4 6.7

Vegetation 2.8 2.8 4.2

Overall Score 1.3 1.3 4.4

Ecological Condition (PES Class)

B B D

Table 6.12: Overall impact scores and PES categories for the target area in Wetland A21C-04 at present (status quo), with rehabilitation and without rehabilitation.








D C E


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6.2 Wetland A21C-05 6.2.1 Wetland ecological functioning Table 6.13 indicate expected ecosystem-services currently performed by the target area in Wetland A21C-05 at the time of the site survey (October 2018), as well as expected changes to ecosystem services that could potentially occur should the proposed rehabilitation strategy be successfully implemented. Wetland habitat will be improved in the target area as sediment trapping will be facilitated within the existing furrow network (Section 7). The most noticeable expected improvements are associated with sediment trapping, erosion control and carbon storage (Table 6.13). The proposed stabilisation of recorded headcuts will also decrease erosion within the target area, which will result increase erosion control (Table 6.13). Table 6.13: Wetland functioning of the target area in Wetland A21C-05, at present and with rehabilitation.



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6.2.2 Wetland importance and sensitivity The Ecological Importance and Sensitivity (EIS) of the assessed target area in Wetland A21C-05 has a Low/Moderate (Class C) (Tables 2.2 and 6.14). This is partially due to the fact that the wetland target area is located within a Threatened Ecosystem (Egoli Granite Grassland) and conservation priority areas (based on C-Plan version 3.3). Little information is available regarding the confirmed presence or absence of Species of Conservation Concern within each wetland (sensu Raimondo et al., 2009), as the wetland survey was undertaken during the end


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of the dry season when plant species are in a dormant stage and not readily visible. Fauna species are also less active during the dry season and may not be present within the site as they are still away on winter migration (e.g. numerous bird species). The overall level of confidence for the EIS component is therefore low. The EIS category is not expected to change from the current scenario to a future post-rehabilitation scenario (Table 6.14). The overall Importance and Sensitivity category for target area decreases with the additional consideration of Hydro-functional Importance and Direct Human Benefits for the current and post-rehabilitation scenarios (Table 6.14). The wetland and its catchment is located within the Rhenosterspruit Conservancy with minimal present day cultivation impacts, direct uses or pollution sources. It is therefore to be expected that hydrological and direct human benefits score low. The proposed rehabilitation strategy will improve the current level of Hydro-functional Importance in the target area (Table 6.14), from a Low/Marginal class to a Moderate class (Tables 2.2 and 6.14). The overall Importance and Sensitivity categories remains the same irrespective of rehabilitation (Table 6.14). Table 6.14: Summary of EIS Scores for the target area in Wetland A21C-05 at present and with rehabilitation.

Current Post-rehab

Ecological Importance and Sensitivity 2.6 2.6





6.2.3 Wetland ecological integrity assessment The ecological integrity, or Present Ecological State (PES), of the target area in Wetland A21C-05 was assessed based on perceived modifications to wetland hydrology, geomorphology and vegetation. These components of the ecological integrity of the wetland were assessed for the current, post-rehabilitation and without rehabilitation scenarios. Impacts affecting the hydrology, geomorphology and vegetation of assessed wetland habitat have already been described in Section 5.3.2. Assessment results that quantify the magnitude of change between the reference condition (Section 5.3.3) and the present condition, as well as the reference condition and the post-rehabilitation condition, are summarised for each wetland health component in Tables 6.15 to 6.17, while the combined results are provide in Table 6.18. Hydrology assessment

No change in the combined hydrological impact score or class is expected in Wetland A21C-05 in the event of rehabilitating the target area in its current state (Table 6.15). Failure to undertake rehabilitation can result in the migration of existing headcut erosion features present in old cultivation furrows, which would further channelise the seep wetland. This can reduce the current hydrology PES class from a B to a C (Table 6.15).


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1.7 1.3 2.5


1.0 1.0 3.0

PES Category B B C


Rehabilitation is expected to decrease the geomorphological impact score and improve its PES class from C to B (Table 6.16). Failure to undertake rehabilitation can result in the migration of existing headcut erosion features through the length of the wetland target area, which will reduce the current geomorphological PES class from a C to an E (Table 6.16). Table 6.16: Geomorphological Impact Scores and PES categories for the target area in Wetland A21C-05 at present (status quo), with rehabilitation and without rehabilitation.







PES Category C B E


Rehabilitation intervention is not expected to improve the vegetation PES class of Wetland A21C-05 as it is likely to remain in a Moderately modified (Class C) PES (Table 6.17). Failure to undertake rehabilitation can result in an increase of the overall vegetation impact score, but the vegetation PES class is not expected to change (Table 6.17).


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Furrows 0.74 0.42 1.64


Vehicle crossing 0.2 0.2 0.2

Remainder 0.12 0.12 0.12


PES Category C C C


For ease of interpretation the scores for hydrology, geomorphology and vegetation are simplified into a composite impact score for the assessed target area by weighting the scores obtained as outlined by Macfarlane et al. (2007). The combined PES class for the target area in Wetland A21C-05 can improve with rehabilitation from a class C (Moderately modified) to a class B (Largely natural), (Table 6.18). This improvement is related to effective sediment trapping and rewetting within furrows in the target area. In the event of no rehabilitation the combined PES can decrease by one category to a class D (Largely modified), (Table 6.18). This decrease is related to the potential advancement of existing headcut erosion features that will extend furrows within the wetland target area. This assessment assumes the worse possible impact, in terms of headcut advancement. There are several unknown factors that can naturally halt headcut advancement within the wetland target area, while recorded headcuts may also remain stable at their current position for many years. Table 6.18: Overall impact scores and PES categories for the target area in Wetland A21C-05 at present (status quo), with rehabilitation and without rehabilitation.








C B D


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6.3 Wetland A21C-08 6.3.1 Wetland ecological functioning Tables 6.19 to 6.21 indicate expected ecosystem-services currently performed by Wetlands A21C-08, A21C-10 and A21C-11 at the time of the site survey (October 2018), as well as expected changes to ecosystem services that could potentially occur should the proposed rehabilitation strategy be successfully implemented. Ecosystem service improvements are not expected in Wetland A21C-08, as only minor intervention will be undertaken to divert flow away from lateral headcut features that appear to be stable for more than 10 years. No change in the provision of ecosystem services are therefore expected in Wetland A21C-08 (Table 6.19). Only a single ecosystem services, namely erosion control, is expected to improve in Wetland A21C-10 due to the proposed rehabilitation strategy (Table 6.20; Section 7). Rehabilitation will stabilise a large headcut in the wetland and contribute to erosion control, without affecting other ecosystem services in a positive or negative manner (Table 6.20) Rehabilitation intervention in Wetland A21C-11 will, however, result in the expected improvement of several ecosystem services, primarily flood attenuation, sediment trapping, erosion control and carbon storage (Table 6.21). Table 6.19: Wetland functioning of the target area in Wetland A21C-08, at present and with rehabilitation.



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Erosion Control 1.6 No change



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Flood Attenuation 1.6 10.4

Stream Flow Regulation 2.0 8.3

Sediment Trapping 2.3 14.8

Phosphate Trapping 2.2 3.8

Nitrate Removal 2.3 4.4

Toxicant Removal 2.0 8.5

Erosion Control 2.3 16.4

Carbon Storage 0.7 100.0


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Water Supply 0.3 58.3



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6.3.2 Wetland importance and sensitivity The Ecological Importance and Sensitivity (EIS) of Wetlands A21C-08, A21C-10 and A21-11 are Low/Marginal, mainly due to erosion and historical cultivation disturbances (Tables 6.22 to 6.24). Wetland A32C-10 has a higher EIS score but remains in the same class as the other two wetlands (Table 6.23). Little information is available regarding the confirmed presence or absence of Species of Conservation Concern within each wetland (sensu Raimondo et al., 2009), as the wetland surveys were undertaken during the end of the dry season when plant species are in a dormant stage and not readily visible. Fauna species are also less active during the dry season and may not be present within the site as they are still away on winter migration (e.g. numerous bird species). The overall level of confidence for the EIS component is therefore low. The EIS category is not expected to change from the current scenario to a future post-rehabilitation scenario in any of the three wetlands (Tables 6.22 to 6.24). The overall Importance and Sensitivity score decrease for all three wetlands with the additional consideration of Hydro-functional Importance and Direct Human Benefits for the current and post-rehabilitation scenarios (Tables 6.22 to 6.24). The wetlands and their catchments are located within the Rhenosterspruit Conservancy with minimal present day cultivation impacts, direct uses or pollution sources. It is therefore to be expected that hydrological and direct human benefits score low. The proposed rehabilitation strategy will maintain the current Hydro-functional Importance score and class in Wetlands A21C-08 and A21C-10 (Tables 6.22 and 6.23) but will improve the class from Low/Marginal to Moderate in Wetland A21C-11 (Table 6.24). Direct Human Benefits remain at the same score and in the same class for all three wetlands, with and without rehabilitation (Tables 6.22 to 6.24). The combined, or overall Importance and Sensitivity categories, remain the same for both wetland target areas irrespective of rehabilitation (Tables 6.22 to 6.24). Table 6.22: Summary of EIS Scores for the target area in Wetland A21C-08 at present and with rehabilitation.

Current Post-rehab







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Current Post-rehab





Overall Importance and Sensitivity Category C C


Current Post-rehab






6.3.3 Wetland ecological integrity assessment The ecological integrity or Present Ecological State (PES) of Wetlands A21C-08, A21C-10 and A21C-11 were assessed based on perceived modifications to wetland hydrology, geomorphology and vegetation. These components of the ecological integrity of the wetland were assessed for the current, post-rehabilitation and without rehabilitation scenarios (See Section 7 for a description of the proposed rehabilitation strategy). Impacts affecting the hydrology, geomorphology and vegetation of assessed wetland areas have already been described in Section 5.4.2. Assessment results that quantify the magnitude of change between the reference condition (Section 5.4.3) and the present condition, as well as the reference condition and the post-rehabilitation condition, are summarised for each wetland health component in Tables 6.25 to 6.35, while the combined results are provide in Table 6.18 for each wetland. Each wetland was assessed separately. Hydrology assessment

No change in the hydrological PES class is expected in Wetlands A21C-08, A21C-10 or A21C-11 in the event of rehabilitation (Tables 6.25 to 6.27). The proposed rehabilitation strategy will therefore only maintain a class E hydrology PES in Wetland A21C-08 and a class C in Wetlands A21C-10 and A21C-11. Failure to undertake rehabilitation is not expected to result in a lower hydrological PES class in Wetland A21C-08, but a downward shift of 2 categories to a class E is possible in Wetland A21C-10, and a single category decrease to a class D in Wetland A21C-11 (Tables 6.25 to 6.27). The decrease in hydrology PES components in Wetlands A21C-10 and A21C-11 are associated with further channelisation as a result of headcut migration in both wetlands. The extent and magnitude of channelisation and erosion is so severe in Wetland A21C-08 that any additional erosion/channelisation impacts are expected to be negligible.


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4.1 4.1 4.1


6.5 6.5 6.5

PES Category E E E







0.5 0.5 4.0


3.0 3.0 6.5

PES Category C C E







0.0 0.0 0.0


3.0 3.0 5.0

PES Category C C D


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No change in the geomorphological PES class is expected in Wetlands A21C-08, A21C-10 or A21C-11 in the event of rehabilitation (Tables 6.28 to 6.30). The proposed rehabilitation strategy will therefore only maintain a class F geomorphological PES in Wetland A21C-08, a class D in Wetland A21C-10 and a class B in Wetland A21C-11. Failure to undertake rehabilitation is not expected to result in a lower geomorphological PES class in Wetland A21C-08, but a downward shift of 2 categories to a class F is possible in Wetland A21C-10, and a lowering by three categories to a class E in Wetland A21C-11 (Tables 6.28 to 6.30). The decrease in geomorphological PES components in Wetlands A21C-10 and A21C-11 are associated with continued headcut migration (advancement) in both wetlands. The extent and magnitude of channel erosion is so severe in Wetland A21C-08 that any additional erosion impacts are expected to be negligible. Table 6.28: Geomorphological Impact Scores and PES categories for the target area in Wetland A21C-08 at present (status quo), with rehabilitation and without rehabilitation.




Infilling 0.3 0.3 0.3

Increased runoff 3.0 3.0 3.0



PES Category F F F






Erosion features 0.1 0 5.6


PES Category D D F


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PES Category B B E


No change in the vegetation PES class is expected in Wetlands A21C-08, A21C-10 or A21C-11 in the event of rehabilitation (Tables 6.31 to 6.33). The proposed rehabilitation strategy will therefore only maintain a class D PES in Wetland A21C-08, and a class C in Wetlands A21C-10 and Wetland A21C-11. Failure to undertake rehabilitation is not expected to result in a lower geomorphological PES class in Wetlands A21C-08, but a downward shift of 1 category to a class D is possible in Wetlands A21C-10 and A21C-11 (Tables 6.31 to 6.33). Table 6.31: Vegetation Impact Scores and PES categories for the target area in Wetland A21C-08 at present (status quo), with rehabilitation and without rehabilitation.





Alien vegetation 0.4 0.4 0.4

Gully erosion 2.8 2.8 2.8

Road crossings 0.2 0.2 0.2

Remainder 0.4 0.4 0.4


PES Category D D D





Erosion gully 0.1 0.1 2.8



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Eroded berm 0.1 0.1 0.1

Alien 0.3 0.3 0.3

Remainder 2.34 2.34 1.32


PES Category C C D






Road crossing 0.1 0.1 0.1

Fire break 0.08 0.08 0.08

Remainder 0.56 0.56 0.2

Erosion gully - - 1.44


PES Category C C D


For ease of interpretation the scores for hydrology, geomorphology and vegetation are simplified into a composite impact score for Wetlands A21C-08, A21C-10 and A21C-11, by weighting the scores obtained as outlined by Macfarlane et al. (2007). The combined PES class for Wetland A21C-08 remains stable with rehabilitation, while it is not expected to decrease at all in the event of no rehabilitation (Table 6.34), as the wetland is already highly modified by extensive erosion caused by the daily release of treated sewage effluent from the upstream Northern WWTW. The combined PES class for Wetland A21C-10 does not improve but is merely maintained by the proposed rehabilitation strategy (Table 6.35). Failure to implement rehabilitation measures to halt a large headcut feature can result in the development of a deep gully throughout the length of the wetland. This is expected to result in a decrease in the overall PES of the wetland to a class E (Table 6.35). The combined PES class for Wetland A21C-11 also does not improve as a result of rehabilitation intervention but will be maintained by the proposed rehabilitation strategy (Table 6.36). Failure to implement rehabilitation measures to halt a headcut feature where a collapsed gabion is currently present, can result in the development of a gully throughout the length of the wetland. This is expected to result in a decrease in the overall PES of the wetland to a class D (Table 6.36). The expected decrease in the overall PES of Wetlands A21C-10 and A21C-11 are driven by the potential advancement of an existing headcut erosion feature at the downstream end of each of the wetlands. Worse-case assumptions were made regarding the possible rate and magnitude of headcut advancement in the assessment of future no-rehabilitation scenarios.


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Several factors that determine headcut advancement remain unknown, such as submerged natural key points that halt headcut advancement. The existing headcuts may also remain stable at their current positions for many years (see Section 7 for further details). Other unpredictable factors that can affect future wetland PES scenarios relate to catchment changes (e.g. continued urbanisation or changes in the release of treated sewage effluent) and unauthorised development within delineated wetlands. Table 6.34: Overall impact scores and PES categories for the target area in Wetland A21C-08 at present (status quo), with rehabilitation and without rehabilitation.








E E E









C C E









C C D


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7. CONCEPT WETLAND REHABILITATION INTERVENTIONS

Wetland rehabilitation can be described as a process in which the causes and symptoms of the wetland degradation are addressed, ensuring the wetland integrity and functionality are maintained and/or improved to a desired state. A proactive approach in terms of corrective interventions is recommended to address the impacts within the wetland systems. The following section serves to describe the rehabilitation of the wetland ecosystems, including the objectives, which attempt to maximise the levels of ecosystem functioning and integrity. The planning of the rehabilitation interventions was carried out by wetland specialist in conjunction with a civil/agricultural engineer, as well as an EAP.

7.1 Wetlands A21C-01 and A21C-04 7.1.1 Problems within wetland target areas Identified wetland impacts that can be rehabilitated at present include the presence of a single headcut at the downstream edge of the target area in Wetland A21C-01 and a deep erosion gully in the target area of Wetland A21C-04 (Figure 7.1).

7.1.2 Rehabilitation aims and objectives within target areas 1 and 2 To aims and objectives of the rehabilitation strategy can be summarised as follow:

• Stabilise the recorded headcut erosion feature in the target area of Wetland A21C-01. • Trap sediment within the erosion gully in order to fill it in and also rewet surrounding

desiccated wetland habitat, in the target area of Wetland A21C-04.

7.1.3 Rehabilitation strategy for all assessed areas The effect of the proposed rehabilitation strategy has been assessed by predicting the anticipated future outcomes of wetland target areas with and without rehabilitation (Tables 7.1 and 7.2). The proposed stabilisation of the recorded headcut in Wetland A21C-01 will not improve the ecological condition (PES class) of the target area but will provide a means of helping to maintain the current PES class by halting further erosion. The headcut has the potential to erode through the entire length of the target area, which can reduce the ecological condition of the wetland from a class B PES to a class D (Table 7.1). Facilitating increased sedimentation and channel in-fill in Wetland A21C-04 will improve the ecological condition of the target area by one category, from a class D to a class C, while continued gully erosion can reduce the PES to a class E (Table 7.2). The functional wetland area secured in Wetland A21C-01 and gained in Wetland A21C-04 can be represented in hectare equivalents based on the method developed by Macfarlane et al. (2012). This is done by converting the overall impact score (that reflects the PES class as described in Table 1) to a level of intactness score (10 – overall impact score) and multiplying this value by the assessed wetland area (i.e. target area). The resultant measure is used as a common currency for evaluating impacts and assessing the change in the ecological condition of an assessed wetland area as a result of continued impacts (e.g. with no rehabilitation) or reduced impacts through the implementation of a rehabilitation strategy (the with rehabilitation scenario).


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Figure 7.1: Target areas for rehabilitation in Wetlands A21C-01 and A21C-04 along with the locations of two proposed rehabilitation interventions, namely A21C-01-210-00 and A21C-04-201-00.


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Using the method developed by Macfarlane (2012) an expected area of 0.9 ha equivalents will be secured as a result of the proposed rehabilitation strategy in the target area of Wetland A21C-01. This is based on a comparison of the expected future scenario with no rehabilitation with the current or future scenario with rehabilitation (Table 7.1). An area of 0.4 ha equivalents can be gained in Wetland A21C-04 when the current and future scenarios with rehabilitation are compared (Table 7.2). A total hectare equivalents area of 0.9 ha will be secured if the expected future scenario with rehabilitation is compared to the future scenario with no rehabilitation scenario (Table 7.2). One proposed intervention is located in each of the wetland target areas (Figure 7.1). Table 7.3 provides a summary of the intervention details, including the type, function, location and priority for implementation for both Wetlands A21C-01 and A21C-04. Table 7.1: Summary of the anticipated effect of the proposed rehabilitation on the ecological integrity of the target area in Wetland A21C-01 at present (status quo), with and without the proposed rehabilitation intervention, and with expected changes in wetland hectare equivalents (Macfarlane et al., 2012).



Size of the assessed target area

3.17 ha






B B D

Hectare Equivalents 2.7 2.7 1.8

Table 7.2: Summary of the anticipated effect of the proposed rehabilitation on the ecological integrity of the target area in Wetland A21C-04 at present (status quo), with and without the proposed rehabilitation intervention, and with expected changes in wetland hectare equivalents (Macfarlane et al., 2012).




2.1 ha






D C E



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Table 7.3: Proposed rehabilitation interventions for target areas in Wetlands A21C-01 and A21C-04 (also refer to Figure 7.1).

Intervention number

Impact Objective of intervention

Intervention type

Location Priority

A21C-01-210-00 Headcut erosion feature located at the downstream edge of the target area

Deactivate the headcut, along a fence

Rock pack/ lining chute

25°52'36.70"S

27°58'14.70"E

1

A21C-04-201-00 Eroded gully with entrenched channel banks

Stabilise the gully, and facilitate sedimentation and infill

Series of silt fences

25°52'56.87"S

27°57'47.41"E

2

7.1.4 Monitoring and evaluation for Wetlands A21C-01 and A21C-04 Figure 7.2 illustrates fixed photos that can be used for monitoring purposed in Wetlands A21C-01 and A21C-04.

Wetland A21C-01

Headcut located at the downstream edge of the target area in Wetland A21C-01 (intervention A21C-01-210-00). Photo taken at coordinates 25°52'37.18"S 27°58'14.71"E.


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Wetland A21C-04

Extensive erosion gully present in the target area of Wetland A21C-04 (intervention A21C-04-201-00). The erosion gully has completely removed wetland topsoil in large areas of the target area. Photo taken at coordinates 25°52'54.19"S 27°57'46.46"E.

Figure 7.2: Monitoring photographs for the target areas in Wetlands A21C-01 and A21C-04.

7.2 Wetland A21C-05 7.2.1 Problems within wetland target area Identified wetland impacts that can be rehabilitated at present include the presence of a series of remnant furrows used for abandoned ridge and furrow cultivation practices, as well as headcuts located in some of the furrows in the target area of Wetland A21C-05 (Figure 7.3).

7.2.2 Rehabilitation aims and objectives within target areas 1 and 2 To aims and objectives of the rehabilitation strategy for the target area in Wetland A21C-05 can be summarised as follow (Figure 7.3):

• Stabilise recorded headcut erosion features in selected furrows. • Trap sediment within selected furrows and rewet surrounding wetland habitat as a

result.

7.2.3 Rehabilitation strategy for all assessed areas The effect of the proposed rehabilitation strategy has been assessed by predicting the anticipated future outcomes of wetland target areas with and without rehabilitation (Table 7.4). The proposed stabilisation of the recorded headcuts, as well as sediment trapping and rewetting in selected furrows, can potentially improve the ecological condition (PES class) of the target area from a class C PES to a class B (Table 7.4). Headcut erosion features can advance further into the wetland target area over time. They appear to remain stable at present, but the combination of a high grazing pressure, a fire event followed by a high intensity rainfall event could result in further headcut erosion. A worse-case scenario of no rehabilitation can decrease the PES from a class C to a class D (Table 7.4). This excludes the impact of catchment transformations, such as future urbanisation, which can further reduce the ecological condition of the wetland.


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Figure 7.3: Target area for rehabilitation in Wetlands A21C-05 along with the locations of all seven proposed rehabilitation interventions.


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The functional wetland area and secured and gained in Wetland A21C-04 can be represented in hectare equivalents based on the method developed by Macfarlane et al. (2012). This is done by converting the overall impact score (that reflects the PES class as described in Table 1) to a level of intactness score (10 – overall impact score) and multiplying this value by the assessed wetland area (i.e. target area). The resultant measure is used as a common currency for evaluating impacts and assessing the change in the ecological condition of an assessed wetland area as a result of continued impacts (e.g. with no rehabilitation) or reduced impacts through the implementation of a rehabilitation strategy (the with rehabilitation scenario). Using the method developed by Macfarlane (2012) an expected area of 1.9 ha equivalents will be secured as a result of the proposed rehabilitation strategy in the target area of Wetland A21C-05. This is based on a comparison of the expected future scenario with no rehabilitation with the current or future scenario with rehabilitation (Table 7.4). In addition, an area of 0.7 ha equivalents can be gained in Wetland A21C-05 when the current and future scenarios with rehabilitation are compared (Table 7.4). A maximum total hectare equivalents area of 2.6 ha can be secured if the expected future scenario with rehabilitation is compared to the future scenario with no rehabilitation scenario (Table 7.4). Seven proposed interventions are located in the wetland target area of Wetland A21C-05 (Figure 7.3). Table 7.5 provides a summary of the intervention details, including the type, function, location and priority for implementation for Wetlands A21C-05. Table 7.4: Summary of the anticipated effect of the proposed rehabilitation on the ecological integrity of the target area in Wetland A21C-05 at present (status quo), with and without the proposed rehabilitation intervention, and with expected changes in wetland hectare equivalents (Macfarlane et al., 2012).




10.4 ha






C B D


Table 7.5: Proposed rehabilitation interventions for the target area in Wetlands A21C-05 (also refer to Figure 7.3).

Intervention number


Intervention type

Location Priority

A21C-05-201-00 Headcut erosion feature located within a furrow

Stabilise the erosion feature

Series of silt fences

25°52'56.87"S

27°57'47.41"E

1


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Intervention number


Intervention type

Location Priority




25°54'10.18"S

27°57'52.40"E

2

A21C-05-203-00 Ridge and furrow creating a wetland desiccation impact

Improve wetland topography and desiccation by levelling out a ridge section and facilitating sedimentation

CCA Poles, Silt fence with Reno downstream

25°54'11.66"S

27°57'53.69"E

7


Improve wetland topography and desiccation by levelling out a ridge section

Cut and fill Ridges (Earthworks) and CC pole weir

25°54'12.24"S

27°57'54.37"E

6


Improve wetland topography and desiccation by levelling out a ridge section

CCA pole weir 25°54'12.69"S

27°57'55.15"E

5




25°54'13.23"S

27°57'55.61"E

3




25°54'14.08"S

27°57'55.77"E

4

7.2.4 Monitoring and evaluation for Wetlands A21C-05 Figure 7.4 illustrates fixed photos that can be used for monitoring purposed in Wetlands A21C-05.


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Headcut located at the proximal end of a furrow (intervention A21C-05-201-00). Photo taken at coordinates 25°54'10.01"S 27°57'51.99"E.

Headcut located within a furrow (intervention A21C-05-202-00). Photo taken at coordinates 25°54'11.51"S 27°57'53.56"E.

Furrow and adjacent ridges (intervention A21C-05-203-00). Photo taken at coordinates 25°54'12.26"S 27°57'53.82"E.



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Figure 7.4: Monitoring photographs for the target area in Wetlands A21C-05.

7.3 Wetland A21C-08 7.3.1 Problems within Wetlands A21C-08, A21C-10 and A21C-11 Identified wetland impacts that can be rehabilitated at present include the presence of large headcut erosion features at the downstream end of Wetland A21C-10 and Wetland A21C-11. Existing gabion structures are present in both wetlands at or close to these headcut features and were recommended in January 2008 (Grobler, 2008). An intact gabion remains present in Wetland A21C-10 (intervention A21C-08-207-01) and only requires maintenance to repair minor damage. It is located upstream of large and unstable headcut feature where no intervention is currently present (proposed intervention A21C-10-202-00), (Figure 7.5). The existing gabion in Wetland A21C-11 has failed completely and is now contributing to worsen erosion damage at the headcut feature it was meant to stabilise (intervention A21C-10-201-01), (Figure 7.5). Wetland A21C-08 has been severely degraded a result of channel erosion. The erosion is of such a magnitude and received such high daily volumes of effluent discharge that no rehabilitation interventions are recommended within the eroded gully. An existing intervention remains stable on the outer left-hand bank of the wetland and was recommended in 2008 in order to stabilise a lateral headcut erosion feature (intervention A21C-08-208-00), (Figure 7.5). Several other lateral headcut erosion features are present along the left-hand


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bank of the channel but appear to have remained stable for the last ten years. Erosion of these lateral headcut features are expected to only result in negligible impacts, considering the extent of existing erosion damage.

7.3.2 Rehabilitation aims and objectives within Wetlands A21C-08, A21C-10 and A21C-11

To aims and objectives of the rehabilitation strategy can be summarised as follow (Figure 7.5):

• Do maintenance work on existing interventions that still remain largely intact. • Remove and replace the rehabilitation intervention that failed completely. • Stabilise recorded headcut erosion features in Wetlands A21C-10and A21C-11. • Divert runoff away from lateral headcuts in Wetland A21C-08 as a precautionary

measure.


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Figure 7.5: Wetlands A21C-08, A21C-10 and A21C-11 along with the locations of existing and proposed rehabilitation interventions.


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7.3.3 Rehabilitation strategy for all assessed areas The effect of the proposed rehabilitation strategy has been assessed by predicting the anticipated future outcomes of wetland target areas with and without rehabilitation (Tables 7.6 to 7.8). The proposed diversion of runoff from lateral headcuts in Wetland A21C-08 to an existing intervention, namely A21C-08-208-00, are not expected to result in any change in the ecological condition of the wetland, nor will it contribute to measurable hectare equivalents gained or secured (Table 7.6). In addition, no change in ecological condition or hectare equivalents are expected in the event that no rehabilitation is undertaken and lateral headcut erosion occurs into terrestrial upslope habitat (Table 7.6). No improvements to the ecological condition or hectare equivalents gained are expected in Wetlands A21C-10 and A21C-11, as the proposed intervention will primarily help to maintain (protect) the status quo. Wetland hectare equivalents are, however, secured, as the future scenarios with no rehabilitation will result in a decrease in the ecological condition (PES class) and wetland hectare equivalents for both Wetlands A21C-10 and A21C-11 (Tables 7.7 and 7.8). It is estimated that wetland hectare equivalents of 0.9 ha and 0.4 ha will be secured in Wetlands A21C-10 and A21C-11 respectively, as a result of the proposed rehabilitation strategy to stabilise headcut erosion features (Tables 7.7 and 7.8). Table 7.6: Summary of the anticipated effect of the proposed rehabilitation on the ecological integrity of Wetland A21C-08 at present (status quo), with and without the proposed rehabilitation intervention, and with expected changes in wetland hectare equivalents (Macfarlane et al., 2012).




6.76 ha






E E E


Table 7.7: Summary of the anticipated effect of the proposed rehabilitation on the ecological integrity of Wetland A21C-10 at present (status quo), with and without the proposed rehabilitation intervention, and with expected changes in wetland hectare equivalents (Macfarlane et al., 2012).




2.59 ha





Page 58





C C E


Table 7.8: Summary of the anticipated effect of the proposed rehabilitation on the ecological integrity of Wetland A21C-11 at present (status quo), with and without the proposed rehabilitation intervention, and with expected changes in wetland hectare equivalents (Macfarlane et al., 2012).




1.21 ha






C C D


A total of six interventions are located in the three wetlands that form part of Wetland A21C-08 (Figure 7.5). Of these six interventions, three are existing interventions, namely A21C-08-207-01, A21C-08-208-00 and A21C-10-201-01 (Figure 7.5). Table 7.9 provides a summary of the intervention details, including the type, function, location and priority for implementation for Wetlands A21C-08, A21C-10 and A21C-11. Table 7.9: Proposed rehabilitation interventions for target areas in Wetlands A21C-01 and A21C-04 (also refer to Figure 7.5).

Intervention number


Intervention type

Location Priority

A21C-08-207-01 Damage to the existing gabion require maintenance to prevent structure failure

Gabion maintenance

Exiting gabion intervention

25°54'35.27"S

27°57'25.08"E

2

A21C-08-208-00 Large actively eroding headcut feature that can advance through the entire Wetland A21C-10

Stabilise the large headcut before it advances and undercuts intervention

New CCA poles, tip-toe configuration / 2 m wide Reno

25°54'34.17"S

27°57'24.18"E

1


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Intervention number


Intervention type

Location Priority

A21C-08-207-01

A21C-10-201-01 Sagging gabion baskets that require maintenance

Gabion maintenance

Exiting gabion intervention

25°54'34.81"S

27°57'14.82"E

5

A21C-10-202-00 Lateral headcut feature located downslope may erode over time

Divert runoff away from the lateral headcuts towards intervention A21C-08-208-00

New rock berm along an existing earth berm that is not a formal intervention

25°54'35.29"S

27°57'20.64"E

6

A21C-11-201-01 Failed gabion structure at a large headcut feature that can advance throughout the entire Wetland A21C-11

Remove material and use for new gabion at intervention A21C-10-202-0, located upslope. Stabilise the headcut with a new intervention at the old located

Existing gabion that has failed completely and new CCA pole fence structure

25°54'35.36"S

27°57'10.86"E

3

A21C-11-202-00 Site selected to slow down water upstream of the large headcut at failed intervention A21C-08-209-01

New gabion structure made from recycled material from intervention A21C-10-201-01

New gabion intervention

25°54'35.73"S

27°57'11.10"E

4

7.3.4 Monitoring and evaluation for Wetlands A21C-08, A21C-10 and A21C-11 Figure 7.6 illustrates fixed photos that can be used for monitoring purposed in Wetlands A21C-08, Wetlands A21C-10 and Wetlands A21C-11.


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Existing intervention A21C-08-207-01 in need of maintenance. Photo taken at coordinates 25°54'35.24"S 27°57'25.23"E.

Existing intervention A21C-10-201-01 in need of maintenance. Photo taken at coordinates 25°54'34.96"S 27°57'14.20"E.

Existing intervention A21C-11-201-01 that will be recycled and replaced with a new CCA-pole and structure. Photo taken at coordinates 25°54'35.29"S 27°57'10.54"E

New intervention A21C-11-202-00 that will be built with recycle gabion material from intervention A21C-11-201-01. Photo taken at coordinates 25°54'35.58"S 27°57'10.99"E.

New intervention A21C-10-201-00 located at headcut where Wetlands A21C-08 and A21C-10 form a confluence. Photo taken at coordinates 25°54'34.17"S 27°57'24.18"E.


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New intervention A21C-10-202-00 that will divert runoff from lateral headcut erosion features in Wetland A21C-08. Photo taken at coordinates 25°54'35.55"S 27°57'16.83"E.

Figure 7.6: Monitoring photographs for new and existing interventions in Wetlands A21C-08, A21C-10 and A21C-11.


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8. REFERENCES Brinson M. 1993. A hydro-geomorphic classification for wetlands. Wetland Research Programme Technical Report WRP-DE-4. US Army Corps of Engineers, Waterways Experiment Station, Vicksburg, MS. Cowden C and Kotze DC, 2008. WET-RehabEvaluate: Guidelines for the monitoring and evaluation of wetland rehabilitation projects. WRC Report No TT 342/08, Water Research Commission, Pretoria. Department of Water Affairs and Forestry (DWAF). 1999. Resource Directed Measures for Protection of Water Resources. Wetland Ecosystems. Version 1.0, September 1999. Department of Water Affairs and Forestry (DWAF). 2005. A practical field procedure for identification and delineation of wetland and riparian areas. DWAF, Pretoria. Department of Water Affairs and Forestry (DWAF). 2008. Updated Manual for the Identification and Delineation of Wetlands and Riparian Areas, prepared by M. Rountree, A. L. Batchelor, J. MacKenzie and D. Hoare. Report no. XXXXXXXXX. Stream Flow Reduction Activities, Department of Water Affairs and Forestry, Pretoria, South Africa. Department of Water and Sanitation (DWS). 2015. PES, EI and ES Scores for sub-quaternary catchments in Secondary Catchment A2. Pretoria, South Africa. GeoTerraImage (GTI), 2015. 2013 - 2014 South African National Land Cover Dataset version 05. DEA Open Access. Obtained from: https://www.environment.gov.za/mapsgraphics. Grundling, P-L. 2015. Wetland Status Quo Report: Madikwe Game Reserve. Specialist report for Aurecon Group. Ixhaphozi Enviro Services. Pretoria. Kleynhans, C.J. (1999). R7: Assessment of Ecological Importance and Sensitivity. Resource Directed Measures for Protection of Water Resources: River Ecosystems Verion 1.0. Institute for Water Quality Studies, Department of Water Affairs and Forestry, Pretoria, South Africa. Kleynhans, C.J., Louw, M.D. & Graham, M. (2008). Module G: EcoClassification and EcoStatus determination in River EcoClassification: Index Of Habitat Integrity (Section 1, Technical Manual) Joint Water Research Commission and Department of Water Affairs and Forestry report. WRC Report No. TT 377-08.


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Kotze, D., Marneweck, G., Batchelor, A., Lindley, D. & Collins, N. 2008. WET-EcoServices. A technique for rapidly assessing ecosystem services supplied by wetlands. Wetland Management Series. WRC Report TT 339/08. Water Research Commission, Pretoria. Macfarlane D.M, Kotze D, Walters D, Ellery W, Koopman V, Goodman P, and Goge C. 2008. WET-Health: A Technique for Rapidly Assessing Wetland Health. Wetland Management Series. WRC Report TT 340/08. Water Research Commission, Pretoria. Macfarlane, D.M., Von Hase, A., and Brownlie, S. 2012. Towards a best-practice guideline for wetland offsets in South Africa. Final Report for the South African National Biodiversity Institute (SANBI) Grassland Programme. Middleton, B.J. & Bailey, A.K. 2008. Water Resources of South Africa, 2005 Study (WR2005). Water Research Commission (WRC) Report TT380/08, Pretoria. Mucina, L. & Rutherford, M.C. (eds) 2006. The Vegetation of South Africa, Lesotho and Swaziland, 1:1 000 000 scale sheet maps. South African National Biodiversity Institute: Pretoria. Nel, J.L., Driver, A., Strydom, W.F., Maherry, A., Petersen, C., Hill, L., Roux, D.J., Nienaber, S., van Deventer, H., Swartz, E., & Smith-Adao, L.B. 2011. Atlas of Freshwater Ecosystem Priority Areas in South Africa: Maps to support sustainable development of water resources. WRC Report No. TT 500/11. Water Research Council, Pretoria. Ollis, D.J., Snaddon, C.D., Job, N.M. & Mboma, N. 2013. Classification System for Wetlands and other Aquatic Ecosystems in South Africa. User Manual: Inland Systems. SANBI Biodiversity Series 22. South African National Biodiversity Institute, Pretoria. Rountree, M.W., Malan, H. & Weston, B. (Editors). 2013. Manual for the Rapid Ecological Reserve Determination of inland wetlands (Version 2.0). Joint Department of Water Affairs/Water Research Commission study. Pretoria.

WORKING FOR WETLANDS

PROVINCE: Gauteng

PROJECT: Gauteng North

Phase 2: Wetland Status Quo Report

DRAFT

Report Reference: Enkangala

Wetland

Page ii

Report Control

Approval

Author signature

Date February 2019 Name Retief Grobler

Title Mr

Document control

Report title Enkangala Phase 2: Wetland Status Quo Report

Document ID Enkangala Client project number

113223

Prepared by Mr Retief Grobler

Client Aurecon South Africa (Pty) Ltd

PO Box 494

Cape Town

8000

On behalf of Working for Wetlands Programme (WfWet)

Department of Environmental Affairs: Natural Resource Management

Private Bag X447

0001

Client contact Ms Franci Gresse

Tel: 021 526 9400

WfWet contact Dr Farai Tererai

Tel: 012 399 8970

Rev Date Revision details/status Approver

0 Draft Report

Contributors

Report reference Working for Wetland Programme. 2019. Enkangala B20H-08 Phase 2: Wetland Status Quo Report. Prepared by Imperata Consulting CC as part of the planning phase for the Working for Wetlands Rehabilitation Programme. Report No.2019.

Working for Wetlands Enkangala Phase 2 Status Quo Report 2019

Page iii

Table of Contents List of Tables .......................................................................................................................................... iv

List of Acronyms ..................................................................................................................................... vi

Glossary of Terms.................................................................................................................................. vii

1. OVERVIEW OF WORKING FOR WETLANDS ..................................................................................... 1

1.1 Objectives of Working for Wetlands ....................................................................................... 1

1.2 Relevant legislation, policies and guidelines applicable to the project .................................. 1

1.3 Introduction to project ........................................................................................................... 2

2. METHODOLOGY .............................................................................................................................. 4

2.1 Assessment of wetland functioning and condition ................................................................ 4

2.1.1 Assessment of wetland functioning ................................................................................ 4

2.1.2 Ecological importance and sensitivity ............................................................................. 5

2.1.3 Assessment of wetland condition/integrity .................................................................... 6

2.2 Monitoring and Evaluation ..................................................................................................... 7

2.2.1 Fixed Point Photography/ Site Photographs ................................................................... 7

2.2.2 Wetland Assessments ..................................................................................................... 8

3. STUDY AREA .................................................................................................................................... 8

3.1 Regional context ..................................................................................................................... 8

3.2 Climate .................................................................................................................................... 8

3.3 Vegetation types ..................................................................................................................... 9

3.4 National Freshwater Ecosystem Priority Areas ....................................................................... 9

4. ASSUMPTIONS AND LIMITATIONS .................................................................................................. 9

5. WETLAND DESCRIPTIONS .............................................................................................................. 10

5.1 Watercourses identified for Rehabilitation Assessment ...................................................... 10

5.2 Wetland B20H-08 .................................................................................................................. 10

5.2.1 Watercourse Details ...................................................................................................... 10



6. STUDY RESULTS ............................................................................................................................. 14

6.1 Wetland B20H-08 .................................................................................................................. 14




7. CONCEPT WETLAND REHABILITATION INTERVENTIONS .............................................................. 22

7.1 Wetland B20H-08 .................................................................................................................. 22


Page iv

7.1.1 Problems within target areas 1 and 2 ........................................................................... 22

7.1.2 Problems within stands of alien trees ........................................................................... 22


7.1.4 Rehabilitation aims and objectives within stands of alien trees .................................. 22


8. REFERENCES .................................................................................................................................. 28

List of Tables Table 1.1: Project area descriptions for Quaternary Catchment B20H included in the study. .............. 2

Table 2.1: Ecosystem services supplied by wetlands (Kotze et al., 2007). ............................................. 5

Table 2.2 Ecological Importance and Sensitivity Classes (DWA, 2013)................................................... 6

Table 2.3: Impact scores and present state categories for describing the integrity of wetlands .......... 7

Table 3.1: The MAP, PET and hydrological sensitivity for Quaternary Catchment B20H (Macfarlane et

al., 2008). ................................................................................................................................................ 8

Table 5.1: Watercourses investigated during the Phase 2 site visit to Enkangala ............................... 10

Table 5.2: Details for Wetland B20H-08. .............................................................................................. 12

Table 5.3: The inferred reference benchmark state of Wetland B20H-08. .......................................... 13

Table 6.1: Wetland functioning of Target area 1 and 2 in Wetland B20H-08, at present and with

rehabilitation......................................................................................................................................... 14

Table 6.2: Wetland functioning of alien tree stands in Wetland B20H-08, at present and with

rehabilitation......................................................................................................................................... 15

Table 6.3: Summary of EIS Scores for the two target areas in Wetland B20H-08 at present and with

rehabilitation......................................................................................................................................... 16

Table 6.4: Summary of EIS Scores for the two stands of alien trees in Wetland B20H-08 at present

and with rehabilitation. ........................................................................................................................ 16

Table 6.5: Hydrological Impact Scores and PES categories for target area 1 in Wetland B20H-08 at


Table 6.6: Hydrological Impact Scores and PES categories for target area 2 in Wetland B20H-08 at


Table 6.7: Hydrological Impact Scores and PES categories for the two stands of alien trees in Wetland

B20H-08 at present (status quo), with rehabilitation and without rehabilitation. .............................. 17

Table 6.8: Geomorphological Impact Scores and PES categories for target area 1 in Wetland B20H-08

at present (status quo), with rehabilitation and without rehabilitation. ............................................. 18

Table 6.9: Geomorphological Impact Scores and PES categories for target area 2 in Wetland B20H-08

at present (status quo), with rehabilitation and without rehabilitation. ............................................. 18

Table 6.10: Geomorphological Impact Scores and PES categories for the two stands of alien trees in

Wetland B20H-08 at present (status quo), with rehabilitation and without rehabilitation. ................ 19

Table 6.11: Vegetation Impact Scores and PES categories for target area 1 in Wetland B20H-08 at


Table 6.12: Vegetation Impact Scores and PES categories for target area 2 in Wetland B20H-08 at


Table 6.13: Vegetation Impact Scores and PES categories for the two stands of alien plants in

Wetland B20H-08 at present (status quo), with rehabilitation and without rehabilitation. ................ 20


Page v

Table 6.14: Overall impact scores and PES categories for target area 1 in Wetland B20H-08 at present

(status quo), after rehabilitation and without rehabilitation. .............................................................. 20

Table 6.15: Overall impact scores and PES categories for target area 2 in Wetland B20H-08 at present

(status quo), after rehabilitation and without rehabilitation. .............................................................. 21

Table 6.16: Overall impact scores and PES categories for the two alien tree stands in Wetland B20H-

08 at present (status quo), after rehabilitation and without rehabilitation. ........................................ 21


integrity of target area 1 in Wetland B20H-08 at present (status quo), with and without the proposed

rehabilitation intervention, and with expected changes in wetland hectare equivalents (Macfarlane

et al., 2012). .......................................................................................................................................... 24


integrity of target area 2 in Wetland B20H-08 at present (status quo), with and without the proposed

rehabilitation intervention, and with expected changes in wetland hectare equivalents (Macfarlane

et al., 2012). .......................................................................................................................................... 24


integrity of the two stands of alien trees in Wetland B20H-08 at present (status quo), with and

without the proposed rehabilitation intervention, and with expected changes in wetland hectare

equivalents (Macfarlane et al., 2012). .................................................................................................. 25

Table 7.4: Proposed rehabilitation interventions for all assessed areas (target areas and stands of

alien trees) in Wetland B20H-09. .......................................................................................................... 26

List of FiguresFigure 1.1: Location Map of Enkangala Wetland, the two target areas and two stands of

alien trees identified for rehabilitation. .................................................................................................. 3

Figure 5.1: Illustrates Wetland B20H-08 along with target areas 1 and 2, two stand of alien trees

dominated by Populus xcanescens and impacts recorded within the target areas. ............................ 11

Figure 5.2: An example of a typical drain within target area 1 (left) and aliens, such as

Populus xcanescens and Ricinus communis (right) in Wetland B20H-08. ............................................. 12

Figure 7.1: Wetland B20H-08 and the location of proposed interventions in the two target areas and

two stands of alien vegetation.............................................................................................................. 23


Page vi

List of Acronyms Acronym Explanation

C-Plan Conservation Plan (typically in the form of a spatial dataset at a provincial level)

DEA Department of Environmental Affairs DWAF Department of Water Affairs and Forestry DWS Department of Water and Sanitation (previously referred to as

the Department of Water Affairs and Forestry) EC Ecological Category EI Ecological Importance EIS Ecological Importance and Sensitivity ES Ecological Sensitivity GDARD Gauteng Department of Agriculture and Ruderal Development HGM unit Hydro-geomorphic unit IHI Index of Habitat Integrity NFEPA National Freshwater Ecosystem Priority Areas PES Present Ecological State WfWet Working for Wetlands WMA Water Management Area


Page vii

Glossary of Terms Term Explanation

Catchment A drainage basin or land area with convergent contour lines where water flow starts and accumulate to form a drainage network. Also referred to as a watershed (specifically in the US), but a watershed can also refer to a catchment divide

Catchment divide Divisions between catchments, located on areas with divergent contour lines.

Channelled valley bottom wetland (HGM unit)

A valley bottom wetland with a river channel running through it. Channelled valley bottom wetlands are characterised by their position on valley floors and the absence of characteristic floodplain features. Dominant water inputs to these wetlands are from the river channel flowing through the wetland either as surface flow resulting from flooding or as subsurface flow, and/or from adjacent valley side slopes (as overland flow or interflow), (Ollis et al. 2013).

Depression wetland (HGM unit)

An inland aquatic ecosystem with closed (or near-closed) elevation contours, which increases in depth from the perimeter to a central area of greatest depth, and within which water typically accumulates Dominant water sources are precipitation, groundwater discharge, interflow and diffuse (or concentrated) overland flow. Dominant hydrodynamics are primarily seasonal with resultant vertical fluctuations (Ollis et al., 2013).

Floodplain wetland (HGM unit)

A wetland area within a floodplain Water and sediment input to these wetlands is mainly via overspill from a river channel during flooding. Floodplains consists of gently sloping land adjacent to, and formed by, an alluvial river channel (Ollis et al., 2013).

Headcut An erosion feature that can develop within a channel, at the proximal end of a channel, or on an unchannelled slope. They are the precursors to channel development as headcut migration create or extent channels.

Hillslope seep wetland (HGM unit)

See seep wetland

Hydro-geomorphic

A type of aquatic ecosystem distinguished primarily on the basis of landform (shape and setting), hydrological characteristics (nature of water movement), and hydrodynamics (direction and strength of water movement), (Ollis et al., 2013).

Hydromorphic soil Soils with features that have developed under anaerobic conditions due to a fluctuating water table or longer periods of saturation

Hydrophyte Plant species that are adapted to wetter areas and can therefore grow in water or soils that are at least periodically saturated and/or inundated. Can also refer to facultative and obligate hydrophyte species to help indicate the gradient of wetness to which a particular species is adapted.

Instream habitat Includes the physical structure of a watercourse and the associated vegetation in relation to the bed of the watercourse (National Water Act, Act No. 36 of 1998), (NWA)


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Term Explanation

Pan wetland See depression wetland. Riparian habitat/zone/area

The physical structure and associated vegetation of the areas associated with a watercourse which are commonly characterized by alluvial soils, and which are inundated or flooded to an extent and with a frequency sufficient to support vegetation of species with a composition and physical structure distinct from those of adjacent land areas (NWA).

River A linear landform with clearly discernible bed and banks, which permanently or periodically carries a concentrated flow of water. A river includes both the active channel and the riparian zone (Ollis et al., 2013)

Seep wetland (HGM unit)

Wetland area located on gently to steeply sloping land and dominated by the colluvial (i.e. gravity-driven), unidirectional movement of water and material down-slope. Seeps are often located on the side-slopes of a valley, but they do not typically, extend unto a valley floor. Water inputs are primarily via subsurface flows from an up-slope direction.

Unchannelled valley bottom wetland (HGM unit)

A valley bottom wetland without a river channel running through it. These wetlands are characterised by the location on valley floors, an absence of distinct channel banks, and the prevalence of diffuse flows. Water inputs are typically from an upstream channel and seepage from adjacent valley side slopes, if present.

Watercourse Watercourse definitions as provided in the NWA:

• A river or spring; • A natural channel in which water flows regularly or intermittently; • A wetland, lake or dam into which, or from which, water flows

and • Any collection of water which the Minister may, by notice in the

Gazette, declare to be a watercourse. A reference to a watercourse includes, where relevant, its bed and banks.

Wetland Land which is transitional between terrestrial and aquatic systems where the water table is usually at or near the surface, or the land is periodically covered with shallow water, and which land in normal circumstances supports or would support vegetation typically adapted to life in saturated soil (NWA).

Wetland flat (HGM unit)

A level or near-level wetland area that is not fed by water from a river channel, and which is typically situated on a plain or bench. Closed elevation contours are not evident around the edge of a wetland flat. They are characterised by the dominance of vertical water movements associated with precipitation, groundwater inflow, infiltration and evaporation. Horizontal water movements within these wetlands, if present, are multi-directional, due to the lack of any significant change in gradient within the wetland (Ollis et al., 2013).


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1. OVERVIEW OF WORKING FOR WETLANDS Working for Wetlands (WfWet) is a government programme managed under the Natural Resource Management Programme (NRM) of the Department of Environmental Affairs (DEA). It is a joint initiative with the Departments of Water and Sanitation (DWS), and Agriculture, Forestry and Fisheries (DAFF). In this way the programme is an expression of the overlapping wetland-related mandates of the three parent departments, and besides giving effect to a range of policy objectives, it also honours South Africa’s commitments under several international agreements, especially the Ramsar Convention on Wetlands. The programme is mandated to protect pristine wetlands, promote their wise-use and rehabilitate those that are degraded throughout South Africa, with an emphasis on complying with the principles of the Expanded Public Works Programme (EPWP) and using only local Small, Medium and Microenterprises (SMMEs). The EPWP seeks to draw significant numbers of unemployed people into the productive sector of the economy, gaining skills while they work and increasing their capacity to earn an income.

1.1 Objectives of Working for Wetlands WfWet engages with provinces, especially government departments and agencies responsible for biodiversity and environment, and municipalities through individual projects. A stronger working relationship with these spheres of government is being promoted through the programme’s emphasis on partnerships. In particular, compatibility with Integrated Development Plans (IDPs) and rehabilitation project objectives will be a key area of future focus. WfWet encourages municipalities to participate in provincial wetland forums because they are the platform for the roll-out of all the programmes processes, including planning for future work. Provincial forums also offer support from the government departments and private sectors that are represented. Partnerships with non-governmental organizations and the private sector are also critical, requiring collaboration and cooperation with a wider range of stakeholders and role players in the wetland management field. The newly identified strategic framework of WfWet has underlined the need for a more refined process that the programme is embarking on with catchment-scale planning. Catchment-scale planning seeks to promote ecosystem-scale outcomes, long-term custodianship, and embedding of rehabilitation in broader local institutions and frameworks. The recent move to a systematic wetland rehabilitation planning process has provided a fertile and conducive platform for partnerships to be formed and/or strengthened as it draws in a much wider stakeholder base. This is in line with NRM’s objective to increase its footprint through Land User Incentive based projects.

1.2 Relevant legislation, policies and guidelines applicable to the project WfWet operates within the context of the Constitution (1996), whereby everyone has the right to an environment that is not harmful to their health and wellbeing, and that is protected. The following national legislation, amongst others, are thus applicable:

• National Environmental Management Act, 1998 (NEMA) • National Environmental Management: Biodiversity Act, No 10 of 2004 (NEMBA) • National Water Act, 1998 (NWA) • Conservation of Agricultural Resources Act, 1993 (CARA) • National Heritage Resources Act, 1999 (Act 25)


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This legislation both directs WfWet in its vision and objectives and regulates the wetland rehabilitation activities which WfWet carries out. WfWet has put in place systems to achieve compliance with all applicable legislation. For example, Basic Assessments for Environmental Authorisation are carried out for all listed activities involved in wetland rehabilitation to comply with NEMA and a Memorandum of Agreement is in place with DWS to ensure compliance with the water licensing requirements of the NWA.

1.3 Introduction to project This wetland status quo report forms part of Phase 2 of the Gauteng North wetland rehabilitation project, which is classified as a Category 2 wetland rehabilitation project. This involves projects where rehabilitation planning is being undertaken in recently prioritized wetlands that are combined with maintenance work in surrounding wetlands present in the area (e.g. Quaternary Catchment B20H). A wetland rehabilitation assessment has been undertaken in the Enkangala Wetland (Wetland B20H-08) for WfWets by Grobler (2016). Extensive rehabilitation work has been undertaken by WfWets in Quaternary Catchment B20H-08 in Ezemvelo Nature Reserve over the last ten years, while maintenance work is also ongoing within the same area. The planned rehabilitation strategy for 2018/2019 will be focussed on two target areas within the wetland, as well as two stands of alien trees and shrubs dominated by Populus xcanescens (Table 1.1; Figure 1.1). Table 1.1: Project area descriptions for Quaternary Catchment B20H included in the study.

Province Gauteng

Quaternary Catchment B20H

Project Name Gauteng North

Land Owner / Partnership City of Tshwane Metropolitan Municipality

Planning Phase Phase 2

Nearest Town Bronkhorstspruit

Previous Work

Several other wetlands were targeted for rehabilitation work in Quaternary Catchment

B20H over the last ten years, including Ezemvelo Nature Reserve and Sokhulumi Wetland (Wetland B20H-04). Enkangala

Wetland is the most recent wetland to receive rehabilitation intervention.

Project Description Category 2


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Figure 1.1: Location Map of Enkangala Wetland, the two target areas and two stands of alien trees identified for rehabilitation.


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2. METHODOLOGY The rehabilitation of freshwater ecosystems is considered to be a complex undertaking and the planning process involves multiple disciplines. The relevant components of the following methodology were adopted for the project and comprised of multiple steps.

2.1 Assessment of wetland functioning and condition Determining the impacts on the wetland habitat requires the assessment and thus understanding of the levels of functioning and condition/integrity of the wetlands for the current and post-rehabilitation scenarios. Wetlands and other types of watercourses, such as headwater ephemeral channels, were delineated through a desktop approach with little emphasis on the identification and recording of watercourse indicators used for delineation purposes. Emphasis was placed on recording indicators associated with the ecological integrity (health) of watercourses watercourse. Suspected problem area in watercourses that may be suitable for rehabilitation were first identified through a desktop approach and investigated on site during the Phase 2 survey on 30 October 2018.

2.1.1 Assessment of wetland functioning To quantify the level of functioning of the wetland systems, and to highlight their relative importance in providing ecosystem benefits and services at a landscape level, a WET-EcoServices (Kotze et al., 2007) assessment was performed for the current and post-rehabilitation scenarios for all the high priority wetland systems identified during the WfWet Phase 1 planning phase. The WET-EcoServices assessment technique focuses on assessing the extent to which a benefit is being supplied by the wetland habitat, based on both:

• The opportunity for the wetland to provide the benefits; and

• The effectiveness of the particular wetland in providing the benefit. Ecosystem services, which include direct and indirect benefits to society and the surrounding landscape, were assessed by rating various characteristics of the wetland and its surrounding catchment, based on the following scale:

• Low (0);

• Moderately Low (1);

• Intermediate (2);

• Moderately High (3); and

• High (4) The scores obtained from these ratings for the wetland systems were then incorporated into WET-EcoServices scores for each of the fifteen ecosystem services (Table 2.1). The same method was used to assess wetlands and ephemeral channels, collectively referred to as watercourses. This was done for the sake of consistency with other similar assessments being undertaken for WfWets across South Africa in addition, non-wetland ephemeral channels are


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expected to provide similar functions as marginal-temporary wetlands in a semi-arid area, such as the study area. Table 2.1: Ecosystem services supplied by wetlands (Kotze et al., 2007).

Eco

syste

m s

erv

ices s

up

plied

by w

etl

an

ds

Ind

irect

ben

efi

ts

Reg

ula

tin

g a

nd

su

pp

ort

ing

ben

efi

ts

Flood attenuation The spreading out and slowing down of floodwaters in the wetland, thereby reducing the severity of floods downstream

Stream flow regulation Sustaining stream flow during low flow periods

Wat

er q

ualit

y en

hanc

emen

t be

nefit

s

Sediment trapping The trapping and retention in the wetland of sediment carried by runoff waters

Phosphate assimilation

Removal by the wetland of phosphates carried by runoff waters

Nitrate assimilation Removal by the wetland of nitrates carried by runoff waters

Toxicant assimilation Removal by the wetland of toxicants (e.g. metals, biocides and salts) carried by runoff waters

Erosion control Controlling of erosion at the wetland site, principally through the protection provided by vegetation

Carbon storage The trapping of carbon by the wetland, principally as soil organic matter

Dir

ect

ben

efi

ts

Biodiversity maintenance Through the provision of habitat and maintenance of natural process by the wetland, a contribution is made to maintaining biodiversity

Pro

vis

ion

ing

ben

efi

ts

Provision of water for human use

The provision of water extracted directly from the wetland for domestic, agricultural or other purposes

Provision of harvestable resources

The provision of natural resources from the wetland, including livestock grazing, craft plants, fish, etc.

Provision of cultivated foods The provision of areas in the wetland favourable for the cultivation of foods

Cu

ltu

ral b

en

efi

ts

Cultural heritage Places of special cultural significance in the wetland, e.g. for baptism or gathering of culturally significant plants

Tourism and recreation Sites of value for tourism and recreation in the wetland, often associated with scenic beauty and abundant birdlife

Education and research Sites of value in the wetland for education or research

2.1.2 Ecological importance and sensitivity In accordance with DWAF (1999), the ecological importance of a water resource provides an expression of its importance to the maintenance of ecological diversity and functioning at local and wider scales. As WET-EcoServices does not provide a consolidated score that can be used as a target, the assessment scores were incorporated into the Ecological Importance and Sensitivity (EIS) assessment framework to provide an EIS score based on scores for ecological importance and sensitivity, hydro-functional importance, and direct human benefits (DWA, 2013). Table 2.2 provides an overview of the ratings used to interpret the derived EIS


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scores. The same method was used to assess wetlands and ephemeral channels, collectively referred to as watercourses. Ephemeral channels and marginal-temporary wetlands in a semi-arid area, such as the study area, are expected to provide similar functions and have similar sensitivities. Table 2.2 Ecological Importance and Sensitivity Classes (DWA, 2013).

Ecological Importance and Sensitivity Categories Range of EIS

Score EIS

Class

Very high: Wetlands that are considered ecologically important and sensitive on a national or even international level. The biodiversity of these systems is usually very sensitive to flow and habitat modifications. They play a major role in moderating the quantity and quality of water of major rivers.

4 A

High: Wetlands that are considered to be ecologically important and sensitive. The biodiversity of these systems may be sensitive to flow and habitat modifications. They play a role in moderating the quality and quantity of water in major rivers.

>3 and <4 B

Moderate: Wetlands that are considered to be ecologically important and sensitive on a provincial or local scale. The biodiversity of these systems is not usually sensitive to flow and habitat modifications. They play a small role in moderating the quantity and quality of water of major river.

>2 and </=3 C

Low/Marginal: Wetlands that are not ecologically important and sensitive at any scale. The biodiversity of these systems is ubiquitous and not sensitive to flow and habitat modifications. They play an insignificant role in moderating the quantity and quality of water of major rivers.

>1 and </=2 D

None: Wetlands that are rarely sensitive to changes in water quality/hydrological regime. 0 E

2.1.3 Assessment of wetland condition/integrity To determine the level of ecological integrity, a WET-Health (MacFarlane et al., 2007) assessment was performed for the current, post-rehabilitation and without rehabilitation scenarios for the wetland systems (where appropriate). The WET-Health assessment technique gives an indication of the deviation of the system from the wetlands’ natural reference condition for the following biophysical drivers:

• Hydrology - defined as the distribution and movement of water through a wetland and its soils;

• Geomorphology - defined as the distribution and retention patterns of sediment within the wetland; and

• Vegetation - defined as the vegetation structural and compositional state. The impacts on the wetlands, determined by features of the wetlands and their catchments, were scored based on the impact scores and then represented as Present State Categories (PES) as outlined in WET-Health (Table 2.3). The wetland catchment was estimated based on interpretation of terrain topography and 1:50000 topographical maps.


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Table 2.3: Impact scores and present state categories for describing the integrity of wetlands

(MacFarlane et al., 2007).

Impact

Category Description

Impact

Score Range

(0-10)

Present

State

Category

None Unmodified, natural. 0-0.9 A

Small Largely natural with few modifications. A slight change in ecosystem processes is discernible and a small loss of natural habitats and biota may have taken place.

1-1.9 B

Moderate Moderately modified. A moderate change in ecosystem processes and loss of natural habitats has taken place but the natural habitat remains predominantly intact.

2-3.9 C

Large Largely modified. A large change in ecosystem processes and loss of natural habitat and biota has occurred. 4-5.9 D

Serious The change in ecosystem processes and loss of natural habitat and biota is great but some remaining natural habitat features are still recognizable.

6-7.9 E

Critical Modifications have reached a critical level and the ecosystem processes have been modified completely with an almost complete loss of natural habitat and biota.

8-10 F

The scores for hydrology, geomorphology and vegetation were simplified into a composite impact score, using the predetermined ratio of 3:2:2 (MacFarlane et al., 2007) respectively for the three components. The composite impact score was used to derive a health score that then provided the basis for the calculation of hectare equivalents (also referred to as functional area), which can be described as the health of a wetland expressed as an area (Kotze and Ellery 2009). Wetland rehabilitation and maintenance planning.

2.2 Monitoring and Evaluation The monitoring and evaluation of the wetlands relies on collecting relevant baseline information, with the collected data including fixed point photographs. Furthermore, it should include the summary of the systems to be rehabilitated, including:

• number of wetlands to be rehabilitated; • number of HGM units to be rehabilitated; • hectare equivalents gained/secured due to the rehabilitation; and • area (hectares) influenced by the proposed rehabilitation activities (only applicable to

wetland watercourses).

2.2.1 Fixed Point Photography/ Site Photographs Pre-implementation photographs were recorded for the wetland and/or wetland complex, as outlined in WET-RehabEvaluate (Cowden and Kotze, 2009), to provide a visual baseline of the system prior to the implementation of the proposed rehabilitation activities. Visual monitoring can then be undertaken in subsequent years to document the changes of the systems.


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2.2.2 Wetland Assessments The ecological integrity and functioning of the wetlands should be monitored using the WET-Health (Macfarlane et al., 2007) and WET-EcoServices (Kotze et al., 2007) assessment techniques. The assessments undertaken for the Phase 2 planning will form the baseline data of the systems from which future assessments of the systems can be based.

3. STUDY AREA The following section provides an overview of the study area, focusing on the regional context, climate, and vegetation types.

3.1 Regional context The Enkangala Wetland and Quaternary Catchment B20H form part of the Olifants Water Management Area (WMA), previously part of the Upper Olifants WMA. The WMA is currently under threat from coal mining-related activities that have resulted in direct wetland habitat loss and low water quality input into wetlands and rivers due to acid mine drainage (AMD). Remaining wetlands in the WMA that can be secured (protected) and/or improved through rehabilitation efforts are therefore regarded as priority systems. Only a single wetland was investigated for potential rehabilitation in the Gauteng North project, namely Wetland B20H-08. The wetland consists of a broad unchannelled valley bottom hydro-geomorphic (HGM) unit that contains seeps that feeds into the valley bottom wetland. These seeps have been delineated as part of the unchannelled valley HGM unit. All of the target areas and the two stands of alien trees are located on seepage components near the outer margins of the wetland.

3.2 Climate This section provides an overview of the climate within the Quaternary Catchment B20H. An understanding of the climate, i.e. the sensitivity of catchments to hydrological impacts influences rehabilitation planning activities. The hydrological vulnerability factor of wetlands within the Quaternary Catchment B20H is High, with a vulnerability factor of 1.1. This is based on mean annual precipitation of 672 mm and a mean annual evaporation of 1764 (Macfarlane et al., 2008; Middleton & Bailey 2008), (Table 3.1). The hydrological sensitivity of wetlands within the quaternary catchment is high as wetlands can be more dependent on seepage water as a source of water input than direct rainfall. Frost is common during winter and rainfall occurs primarily as thundershowers during the summer months (Mucina and Rutherford, 2006). Table 3.1: The MAP, PET and hydrological sensitivity for Quaternary Catchment B20H (Macfarlane et al., 2008).

Quaternary catchment

MAP (mm)

PET (mm)

MAP:PET ratio Vulnerability factor

Hydrological sensitivity

B20H 1764 672 0.38 1.05 High


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3.3 Vegetation types The entire wetland and its catchment overlaps with the Rand Highveld Grassland vegetation unit described by Mucina and Rutherford (2006). This vegetation unit is a Threatened Ecosystem area according to the 2011 Schedule (Government Gazette of December 2011) of the National Environmental Biodiversity Act (Act 10 of 2004). The Rand Highveld Grassland Threatened Ecosystem (Gm 11) has a Vulnerable conservation status.

3.4 National Freshwater Ecosystem Priority Areas The National Freshwater Ecosystem Priority Areas (NFEPA) is a tool developed to assist in the conservation and sustainable use of South Africa’s freshwater ecosystems, including rivers, wetlands and estuaries. The delineated wetland area overlaps with both priority and non-priority NFEPA wetlands, all of which are classified as a channelled valley bottom wetlands (Nel et al., 2011).

4. ASSUMPTIONS AND LIMITATIONS It is important to note that this assessment was undertaken in a short period of time, with limited field verification. There are therefore a number of limitations to this assessment as outlined below:

• Wetland boundaries are estimated primarily through a desktop approach that made used of time series aerial imagery. A limited amount of time was spent on verifying watercourse boundaries during the site visit. No soil auguring was undertaken but exposed soil profiles, such as channel banks, were inspected where present.

• The wetland catchment area was also delineated through an on-screen digitising desktop approach based on the interpretation of available 5 m contour lines; no GIS modelling was undertaken based on digital elevation models (DEMs).

• Assessment of impacts and rehabilitation outcomes is informed by a structured process, but is based to a large extend on a qualitative rather than a quantitative approach. The latter is associated with the collection of more detailed information related to the hydrology, geomorphology and vegetation components of investigated wetlands.

• Watercourses surveys are timed to overlap with the dry season in Gauteng Province, which enables a better identification of erosion, sedimentation and drainage impacts, but restricts the collection of vegetation and floristic data in surveyed watercourses.

• It follows that the vegetation component does not inform the PES assessments as accurately as it would have during a wet season survey.

• The level of confidence in the accuracy of the assessed Ecological Importance and Sensitivity (EIS) of each wetland is also reduced by dry season surveys, as the identification of plant species of conservation concern (sensu Raimondo et al., 2009) is restricted during the dry season.

• Limited time was available for watercourse indicator analyses, while the timing of the survey occurred at the end of the dry season when hydrophyte (wetland plant) indicators are still in a dormant phase and not easily identifiable.

• Decisions regarding the suitability for rehabilitation at a specific impact are made on site based on an evaluation by the wetland specialist, engineer and provincial coordinator. Wetland and watercourse assessments are only undertaken afterwards in an attempt to quantify what the contribution of the proposed rehabilitation will be for the targeted watercourse area.


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5. WETLAND DESCRIPTIONS 5.1 Watercourses identified for Rehabilitation Assessment Only surveyed wetland sections are assessed in terms of their ecological condition, functioning and sensitivity. This is done as the proposed rehabilitation strategy presented in this report will not improve and/or stabilise (protect) the entire delineated wetland, but only targeted portions thereof. Affected and assessed sections are referred to as target areas. Two target areas have been surveyed during the October 2018 site visit, as well as two stands of alien trees (Figure 1.1 and Figure 5.1). The latter are dominated by the alien species Populus xcanescens, but also contain open patches of old lands that have not yet been encroached by P. xcanescens. Surveyed target areas and alien stands contain temporary, seasonal and permanent wetness zones. Table 5.1: Watercourses investigated during the Phase 2 site visit to Enkangala

Wetland Number

Name Watercourse type

Hydro-geomorphic unit

Surface area (delineated watercourse)

B20H-08 Enkangala Wetland Wetland

Unchannelled valley bottom with broad seeps in its outer zones

314.4 ha

5.2 Wetland B20H-08 5.2.1 Watercourse Details Wetland B20H-08 is located in a first order drainage line position and forms a tributary of the Olifants River. Wetland B20H-08 can best be described as an unchannelled valley bottom hydro-geomorphic (HGM) unit that contains broad seep zones on its outer margins. Figure 5.1 illustrate Wetland B20H-08, while Table 5.2 provides a summary of the wetland. Delineated target areas and the stands of alien vegetation are all located on seep HGM units located on the outer margins of the unchannelled valley bottom wetland. The two target areas and stands of the alien tree, Populus xcanescens, overlap with Ecological Support Areas and Important Areas. The latter refers specifically to Red Listed bird habitat, a priority catchment area and primary vegetation (GDARD, 2012). A portion of the wetland was previously assessed and described by Grobler (2016). This report provides details in of new proposed rehabilitation work in new wetland areas (target areas) that were not evaluated in 2016 (Figure 5.1).


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Figure 5.1: Illustrates Wetland B20H-08 along with target areas 1 and 2, two stand of alien trees dominated by Populus xcanescens and impacts recorded within the target areas.


Table 5.2: Details for Wetland B20H-08.

Wetland Name Enkangala

Wetland Number/Label B20H-08

GPS Location 25°40'31.90"S 28°44'16.95"E

Catchment Land Use Conservation area consisting of clayey thornveld

Catchment Size 2164.14 ha

Wetland Type (HGM unit) Seep (outer margins for a larger unchannelled valley bottom HGM. Only seeps are assessed in this study due to the locations of the target areas and stands of

alien vegetation targeted for rehabilitation)

Wetland Land Use Grassland and urban village are the main catchment land uses




Alien Trees Size (Combined) 7.9 ha

5.2.2 Wetland Characteristics Historically the Enkangala Wetland and target areas were situated in a rural setting with cultivation being the most prominent land use, as is evident from the presence of several crop fields in an aerial photograph from 1939 (Grobler, 2016). Over time the wetland became more impacted by residential development in the form of Dark City and Enkangala settlements, which have encroached into Enkangala Wetland. Commercial cultivation within the wetland and target areas have decreased overtime, while subsistence cultivation and livestock grazing increased. A high grazing pressure is currently present within the wetland, while portions of target area 2 are still actively cultivated (Figure 5.1). Remnants of historical and current cultivation practices are noticeable in the series of agricultural drains that are present in the wetland and target areas (Figures 5.1 and 5.2).

Figure 5.2: An example of a typical drain within target area 1 (left) and aliens, such as Populus xcanescens and Ricinus communis (right) in Wetland B20H-08.


5.2.3 Benchmark or reference state The inferred reference state of Wetland B20H-08 is described in Table 5.3

Table 5.3: The inferred reference benchmark state of Wetland B20H-08.


HGM Unit Seep zones located on the outer margins of a larger unchannelled valley bottom HGM unit


Temporary and seasonal/permanent wetness zones were historically present without a natural channel in any of the target areas or stands of alien vegetation. Interflow in the soil horizon is very common in the wetland across wide seep zones with E horizons expected to be present. Catchment changes are driven by urbanisation, which has reduced infiltration and interflow into the wetland.

Geomorphology Erosion feature are generally absent from seep components in the wetland expect where stormwater channels have started to erode due to higher energy flow events from residential areas. The wetland remains susceptible to deposition and dumping from residential areas as it is unfenced.

Vegetation Alien species have encroached into the wetland due to disturbances caused by sewage leakages, infrastructure construction and especially due to widespread historical cultivation practices. The majority of the wetland has secondary vegetation as a result of historical cultivation as seen on a georeferenced aerial photograph of the area from 1939 (Grobler, 2016). Grazing pressure is currently high and uncontrolled within the wetland.


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6. STUDY RESULTS 6.1 Wetland B20H-08 6.1.1 Wetland ecological functioning Tables 6.1 and 6.2 indicate expected ecosystem-services currently performed by the two target areas at the time of the site survey (October 2018), as well as expected changes to ecosystem services that could potentially occur should the proposed rehabilitation interventions be successfully implemented. The most noticeable expected improvements associated with rewetting in the target areas include an increase in carbon storage and improved erosion control (Table 6.1). Water quality benefits are also expected as water will have a longer retention time in both target areas (Table 6.1) A decrease in flood attenuation is expected in rehabilitated stands with alien trees as the frictional surface of the affected wetland areas will be lowered (Table 6.2). The main improvements include an improved biodiversity with fewer alien species and improved carbon storage (Table 6.2). Other ecosystem services include grazing across the wetland and cultivation in target area 2. Several families cultivate crops such as spinach, tomato and green pepper within target area 2. Water is abstracted for irrigation from one of the larger drains within target area 2. No rehabilitation intervention will be undertaken within cultivated lands. Table 6.1: Wetland functioning of Target area 1 and 2 in Wetland B20H-08, at present and with rehabilitation.



Reg

ula

tory

an

d S

up

po

rtin

g

Serv

ices










Pro

vis

ion

ing

Serv

ices




Cu

ltu

ral

Serv

ices





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Table 6.2: Wetland functioning of alien tree stands in Wetland B20H-08, at present and with rehabilitation.



Reg

ula

tory

an

d S

up

po

rtin

g

Serv

ices

Flood Attenuation 2.0 -8.3 %






Erosion Control 2.7 -4.6 %



Pro

vis

ion

ing

Serv

ices




Cu

ltu

ral

Serv

ices




6.1.2 Wetland importance and sensitivity The scoring assessments for these three aspects of ecological importance and sensitivity have been based on the requirements of the National Water Act, Act No. 36 of 1998 (NWA), the original Ecological Importance and Sensitivity assessments developed for riverine assessments (DWAF, 1999), and the work conducted by Kotze et al. (2005) on the assessment of wetland functions (the WET-EcoServices tool). The EIS of the assessed target areas and stands of alien trees is regarded as Low/Marginal in spite of the presence of the wetland in a Threatened Ecosystem (Rand Highveld Grassland) and the presence of Important Areas and Ecological Support Areas based on C-Plan version 3.3 (Tables 6.3 and 6.4). The majority of wetland vegetation is secondary due to historic cultivation practices throughout Wetland B20H-08. Hydrological functioning is expected to increase in all affected areas in response to rehabilitation, while the majority of remaining functions are expected to remain the same (Tables 6.3 and 6.4).


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Table 6.3: Summary of EIS Scores for the two target areas in Wetland B20H-08 at present and with rehabilitation.

Current Post-rehab






Table 6.4: Summary of EIS Scores for the two stands of alien trees in Wetland B20H-08 at present and with rehabilitation.

Current Post-rehab






6.1.3 Wetland ecological integrity assessment The ecological integrity or Present Ecological State (PES) of the wetland target area was assessed based on modifications to it hydrology, geomorphology and vegetation. These components of the ecological integrity of the wetland were assessed for the current, post-rehabilitation and without rehabilitation scenarios. Each of the two wetland target areas have been assessed separately, while the two stands of alien trees dominated by Populus xcanescens have been assessed together due to their shared similarity (Figures 1.1 and 5.1). The assessment results of the hydrological, geomorphic and vegetation components are outlined in the following sections and summarised in Tables 6.5 to 6.16. Assessment of hydrological impacts

Rehabilitation will deactivate drains in target areas and remove alien trees, such as Populus xcanescens, which has a higher on-site water use compared to indigenous species (Figure 5.1and Figure 5.2). The effect of each of these changes will result in increased wetness regimes. No noticeable hydrological change occurs in target area 1 (PES remains in a class C), while target area 2 improves from a class E to a class D PES and the stands of aliens improve from a class E to a class C PES (Tables 6.5 to 6.7). The absence of rehabilitation is not expected to result in a hydrological PES class decrease compared to the status quo condition in any of the target areas or stands of alien trees (Tables 6.5 to 6.7). However, the impact of increased urbanisation in the catchment and even within Wetland B20H-08 is difficult to predict and further decreases in the hydrological integrity can still occur. The long-term trajectory of hydrological integrity is expected to decrease all of the assessed areas and Wetland B20H-08 itself.


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Table 6.5: Hydrological Impact Scores and PES categories for target area 1 in Wetland B20H-08 at present (status quo), with rehabilitation and without rehabilitation.






1.0 0.6 1.0


3.5 3.5 3.5

PES Category C C C

Table 6.6: Hydrological Impact Scores and PES categories for target area 2 in Wetland B20H-08 at present (status quo), with rehabilitation and without rehabilitation.






4.3 3.8 4.3


6.5 4.0 6.5

PES Category E D E

Table 6.7: Hydrological Impact Scores and PES categories for the two stands of alien trees in Wetland B20H-08 at present (status quo), with rehabilitation and without rehabilitation.






4.8 0.9 6.6


6.5 3.0 7.5

PES Category E C E


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Assessment of geomorphological impacts

The geomorphological integrity of all assessed wetland areas remains consistently in the same PES class irrespective of the presence or absence of rehabilitation (Tables 6.8 to 6.10). Wetland target area 1 remains in a Largely modified (class D) PES, which is one class lower than target area 2, which is Moderately modified (class C PES), as the catchment of the former is more urbanised with more runoff (Tables 6.8 and 6.9). Stands of alien vegetation also remain in a class D PES (Table 6.10) No actively eroding headcut feature was recorded within any of the assessed wetland areas, while drains within the two targets areas appear to be stable and well vegetated. The rehabilitation strategy will therefore not primarily focus on stabilising existing erosion or increasing the sediment trapping potential of assessed wetland areas. The effect of catchment change and dumping or infilling within the target areas are difficult to predict. Wetland B20H-08 is not fenced and provides an easily accessible area for illegal dumping and infilling. A decrease in geomorphological integrity of all of the assessed areas and the whole of Wetland B20H-08 over the long-term is therefore anticipated, but these changes are not expected to be associated with the proposed rehabilitation strategy not being implemented (Section 7). No further negative changes to geomorphological integrity that will result in a PES class change are expected in the short-term (the next five years) (Tables 6.8 to 6.10). Table 6.8: Geomorphological Impact Scores and PES categories for target area 1 in Wetland B20H-08 at present (status quo), with rehabilitation and without rehabilitation.






PES Category D D D

Table 6.9: Geomorphological Impact Scores and PES categories for target area 2 in Wetland B20H-08 at present (status quo), with rehabilitation and without rehabilitation.






PES Category C C C


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Table 6.10: Geomorphological Impact Scores and PES categories for the two stands of alien trees in Wetland B20H-08 at present (status quo), with rehabilitation and without rehabilitation.




Infilling 5.0 5.0 5.0


PES Category D D D


The vegetation of the wetland is impacted by a high grazing pressure throughout Wetland B20H-08, current cultivation in approximately 35 % of target area 2, historical cultivation throughout the wetland and the presence of stands of alien trees (Figure 5.1). Alien vegetation in the two delineated stands of alien trees consist primarily of shrubs of Populus xcanescens that are continuing to expand within Wetland B20H-08 (Figure 5.2). Other alien species, such as Ricinis communis are also present within these two areas, while the alien tree Acacia dealbata was recorded in wetlands sections located outside of assessed areas. Vegetation within the target areas are generally absent of alien species, apart from expected ruderal and agrestal aliens in the cultivated area where no rehabilitation intervention will take place. Vegetation in drains are noticeable adapted to wetter conditions and often include indigenous obligate hydrophytes common in the Highveld, such as Kylinga sp., Juncus lomatophyllus, Pycreus sp., Typha capensis, Phragmites australis, Imperata cylindrica, and a carnivorous Drosera sp. The orchid, Disa woodii, was recorded next to one of the drains in target area 1. The status quo vegetation wetland health component of Target area 2 (class D PES) is in a lower category compared to target area 1 (class C PES) due to the presence of cultivated crops in the latter (Tables 6.11 and 6.12). The vegetation integrity will only be marginally affected within the two target areas, but is expected to remain within the same PES class with and without rehabilitation over the next five years (Tables 6.11 and 6.12). The control of woody alien species, such as Populus xcanescens, in the two stands of alien trees, will improve the current vegetation PES from a class E to a class C, in the event of successful initial and follow-up controls (Table 6.13). Failure to control aliens within the two areas will result in further encroachment of alien species over the next five years with a resultant decrease in the PES class (Table 6.13). Table 6.11: Vegetation Impact Scores and PES categories for target area 1 in Wetland B20H-08 at present (status quo), with rehabilitation and without rehabilitation.




Drains 0.4 0.3 0.4



PES Category C C C


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Table 6.12: Vegetation Impact Scores and PES categories for target area 2 in Wetland B20H-08 at present (status quo), with rehabilitation and without rehabilitation.




Drains (in cultivated land and not targeted for rehabilitation)

0.4 0.4 0.4

Cultivated lands 3.15 3.15 3.15

Old lands 1.11 1.11 1.11

Dams 0.8 0.8 0.8

Drains (targeted for rehabilitation)

0.4 0.3 0.4


PES Category D D D

Table 6.13: Vegetation Impact Scores and PES categories for the two stands of alien plants in Wetland B20H-08 at present (status quo), with rehabilitation and without rehabilitation.




Stands of alien trees and vegetation

4.95 2.2 5.5



PES Category E C F


For ease of interpretation the scores for hydrology, geomorphology and vegetation are simplified into a composite impact score for the target area by weighting the scores obtained as outlined by Macfarlane et al. (2007). The combined PES of target areas 1 and 2 remain in class C and D respectively, with and without rehabilitation intervention, over the next foreseeable five years (Tables 6.14 and 6.15). The combined PES class for the two stands of alien trees improves from a class E to a class C with rehabilitation intervention (Table 6.16). Table 6.14: Overall impact scores and PES categories for target area 1 in Wetland B20H-08 at present (status quo), after rehabilitation and without rehabilitation.







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C C C

Table 6.15: Overall impact scores and PES categories for target area 2 in Wetland B20H-08 at present (status quo), after rehabilitation and without rehabilitation.








D D D6.5

Table 6.16: Overall impact scores and PES categories for the two alien tree stands in Wetland B20H-08 at present (status quo), after rehabilitation and without rehabilitation.








E C E


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7. CONCEPT WETLAND REHABILITATION INTERVENTIONS

Wetland rehabilitation can be described as a process in which the causes and symptoms of the wetland degradation are addressed, ensuring the wetland integrity and functionality are maintained and/or improved to a desired state. A proactive approach in terms of corrective interventions is recommended to address the impacts within the wetland systems. The following section serves to describe the rehabilitation of the wetland ecosystems, including the objectives, which attempt to maximise the levels of ecosystem functioning and integrity. The planning of the rehabilitation interventions was carried out by wetland specialist in conjunction with a civil/agricultural engineer, as well as an EAP.

7.1 Wetland B20H-08 7.1.1 Problems within target areas 1 and 2 Identified wetland impacts that can be rehabilitated at present include the presence of several drains used both historically and presently for cultivation in both target areas (Figure 7.1). These drains remain open and cause an ongoing desiccation effect on surrounding wetland habitat.

7.1.2 Problems within stands of alien trees Alien shrubs and trees create a shading effect that is unfavourable for wetland species adapted to broad seeps and valley bottom wetlands systems on the Highveld. The establishment of woody alien species, such as Populus xcanescens, are able to outcompete indigenous wetland plant species and reduce the diversity of indigenous species. Alien shrubs and trees also have a higher on-site water usage, which causes a desiccation effect (Macfarlane et al., 2008). This desiccation effect increases as the stands expand and individuals develop into fully grown trees.

7.1.3 Rehabilitation aims and objectives within target areas 1 and 2 Blocking existing drains and thereby reducing flow velocities and increasing the retention time of water within the two target areas. In addition, localised rewetting of wetland areas adjacent to furrows will also be achieved.

7.1.4 Rehabilitation aims and objectives within stands of alien trees The targeted control of woody alien species, such as Populus xcanescens, to improve the indigenous biodiversity and reduce on-site water usage.

7.1.5 Rehabilitation strategy for all assessed areas The proposed rehabilitation strategy of blocking drains is not expected to change the PES class of either target area 1 or 2, as discussed in Section 6.1.3 (Tables 7.1 and 7.2). However, at a finer scale, functional wetland areas, referred to as hectare equivalents, can be used to determine losses and gains in the ecological condition of a wetland for different scenarios (e.g. with or without the implementation of rehabilitation measures), (Macfarlane et al., 2012).


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Figure 7.1: Wetland B20H-08 and the location of proposed interventions in the two target areas and two stands of alien vegetation.


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This is done by converting the overall impact score (that reflects the PES class as described in Table 1) to a level of intactness score (10 – overall impact score) and multiplying this value by the assessed wetland area (i.e. target area). The resultant measure is used as a common currency for evaluating impacts and assessing the change in the ecological condition of a wetland or wetland disturbance units as a result of continued impacts (e.g. with no rehabilitation) or reduced impacts through the implementation of a rehabilitation strategy. Tables 7.1 and 7.2 indicate that wetland hectare equivalents of 0.2 ha and 1.3 ha can be secured as a result of the proposed rehabilitation strategy in target areas 1 and 2 respectively. The proposed rehabilitation strategy will therefore not result in no change to the ecological condition of the assessed areas, as indicated by a comparison of PES classes only, but will resulted in an expected combined increase of 1.5 hectare equivalents (Tables 7.1and 7.2). Table 7.1: Summary of the anticipated effect of the proposed rehabilitation on the ecological integrity of target area 1 in Wetland B20H-08 at present (status quo), with and without the proposed rehabilitation intervention, and with expected changes in wetland hectare equivalents (Macfarlane et al., 2012).








C C C

Hectare equivalents 4.2 4.4 4.4

Table 7.2: Summary of the anticipated effect of the proposed rehabilitation on the ecological integrity of target area 2 in Wetland B20H-08 at present (status quo), with and without the proposed rehabilitation intervention, and with expected changes in wetland hectare equivalents (Macfarlane et al., 2012).








D D D



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The proposed rehabilitation strategy of controlling woody alien species within the two stands of alien trees will result in an increase of two PES classes, from class E to class C. In addition, a projected increase of 1.9 ha of wetland hectare equivalents is expected in the wetland (Table 7.3). These improvements are, however, dependant on a successful rehabilitation strategy of alien control with a sufficient number of follow-up controls. It should be noted that these wetland hectare equivalents and gains in the PES class will be lost in the event that woody alien species again become established and dominant within the assessed wetland areas. Table 7.3: Summary of the anticipated effect of the proposed rehabilitation on the ecological integrity of the two stands of alien trees in Wetland B20H-08 at present (status quo), with and without the proposed rehabilitation intervention, and with expected changes in wetland hectare equivalents (Macfarlane et al., 2012).








E C E


The combined wetland hectare equivalents gained from all assessed wetland areas is calculated to be 3.4 ha (Tables 7.1 to 7.3). These gains are associated with the successful implementation and maintenance of a total of 12 interventions and one interventions that has been changed into a monitoring point for now (intervention B20H-08-224-00), (Figure 7.1; Table 7.4).


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Table 7.4: Proposed rehabilitation interventions for all assessed areas (target areas and stands of alien trees) in Wetland B20H-09.

Intervention number Impact Objective of intervention Intervention type Latitude (S) Longitude (E)

Priority

B20H-08-215-00 Drain causing the desiccation of wetland habitat along its length

Deactivate channel flow and encourage dispersed surface flow

Series of Earth Plugs at 20 m intervals

25°40'30.75"S 28°44'43.85"E 10



Drop inlet concrete Weir (V)

25°40'29.19"S 28°44'43.81"E 9



Drop inlet weir 25°40'23.91"S 28°44'50.67"E 8


Raise water height and deactivate drain

Earth Plug 25°40'20.30"S 28°44'53.67"E 7



Cut and Plug at 20 m intervals (Earth works)

25°40'15.15"S 28°44'52.66"E 6



Series of Earth Plugs 25°40'27.98"S 28°44'39.61"E 5



Earth Structure (cut and fill

25°40'12.14"S 28°44'14.92"E 4



Cut, fill and Plug (Earthworks)

25°40'30.75"S 28°44'43.85"E 3


Redirect & slow down stream flow velocity to prevent further

Gabion and Earth Plugs

25°40'29.19"S 28°44'43.81"E 2


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Intervention number Impact Objective of intervention Intervention type Latitude (S) Longitude (E)

Priority

B20H-08-223-00B Drain causing the desiccation of wetland habitat along its length

embankment erosion & trap sediment

Gabion and Earth Plugs (end)

25°40'23.91"S 28°44'50.67"E 1

B20H-08-224-00 Lateral headcut erosion feature located outside of target areas 1 and 2, as well as the delineated stands of alien trees.

It was decided to change this feature from an intervention to a monitoring point. With the intention that monitoring should be done until the next survey before an erosion stabilisation structure is constructed.

Monitoring point for the present time. The proposed intervention that has been suggested Is a Stone Masonry Rock Chute

25°40'20.30"S 28°44'53.67"E 13



Series of earth plugs 25°40'15.15"S 28°44'52.66"E 11

B20H-08-226-00 Intervention includes two stands of woody alien vegetation stands, primarily Populus xcanescens

Protect and provide habitat for wetland vegetation to become re-established

Clearance of Alien Vegetation (Poplar)

25°40'12.14"S

28°44'14.92"E

12


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8. REFERENCES Brinson M. 1993. A hydro-geomorphic classification for wetlands. Wetland Research Programme Technical Report WRP-DE-4. US Army Corps of Engineers, Waterways Experiment Station, Vicksburg, MS. Cowden C and Kotze DC, 2008. WET-RehabEvaluate: Guidelines for the monitoring and evaluation of wetland rehabilitation projects. WRC Report No TT 342/08, Water Research Commission, Pretoria. Department of Water Affairs and Forestry (DWAF). 1999. Resource Directed Measures for Protection of Water Resources. Wetland Ecosystems. Version 1.0, September 1999. Department of Water Affairs and Forestry (DWAF). 2005. A practical field procedure for identification and delineation of wetland and riparian areas. DWAF, Pretoria. Department of Water Affairs and Forestry (DWAF). 2008. Updated Manual for the Identification and Delineation of Wetlands and Riparian Areas, prepared by M. Rountree, A. L. Batchelor, J. MacKenzie and D. Hoare. Report no. XXXXXXXXX. Stream Flow Reduction Activities, Department of Water Affairs and Forestry, Pretoria, South Africa. Department of Water and Sanitation (DWS). 2015. PES, EI and ES Scores for sub-quaternary catchments in Secondary Catchment A2. Pretoria, South Africa. GeoTerraImage (GTI), 2015. 2013 - 2014 South African National Land Cover Dataset version 05. DEA Open Access. Obtained from: https://www.environment.gov.za/mapsgraphics. Grundling, P-L. 2015. Wetland Status Quo Report: Madikwe Game Reserve. Specialist report for Aurecon Group. Ixhaphozi Enviro Services. Pretoria. Kleynhans, C.J. (1999). R7: Assessment of Ecological Importance and Sensitivity. Resource Directed Measures for Protection of Water Resources: River Ecosystems Verion 1.0. Institute for Water Quality Studies, Department of Water Affairs and Forestry, Pretoria, South Africa. Kleynhans, C.J., Louw, M.D. & Graham, M. (2008). Module G: EcoClassification and EcoStatus determination in River EcoClassification: Index Of Habitat Integrity (Section 1, Technical Manual) Joint Water Research Commission and Department of Water Affairs and Forestry report. WRC Report No. TT 377-08.


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Kotze, D., Marneweck, G., Batchelor, A., Lindley, D. & Collins, N. 2008. WET-EcoServices. A technique for rapidly assessing ecosystem services supplied by wetlands. Wetland Management Series. WRC Report TT 339/08. Water Research Commission, Pretoria. Macfarlane D.M, Kotze D, Walters D, Ellery W, Koopman V, Goodman P, and Goge C. 2008. WET-Health: A Technique for Rapidly Assessing Wetland Health. Wetland Management Series. WRC Report TT 340/08. Water Research Commission, Pretoria. Macfarlane, D.M., Von Hase, A., and Brownlie, S. 2012. Towards a best-practice guideline for wetland offsets in South Africa. Final Report for the South African National Biodiversity Institute (SANBI) Grassland Programme. Middleton, B.J. & Bailey, A.K. 2008. Water Resources of South Africa, 2005 Study (WR2005). Water Research Commission (WRC) Report TT380/08, Pretoria. Mucina, L. & Rutherford, M.C. (eds) 2006. The Vegetation of South Africa, Lesotho and Swaziland, 1:1 000 000 scale sheet maps. South African National Biodiversity Institute: Pretoria. Nel, J.L., Driver, A., Strydom, W.F., Maherry, A., Petersen, C., Hill, L., Roux, D.J., Nienaber, S., van Deventer, H., Swartz, E., & Smith-Adao, L.B. 2011. Atlas of Freshwater Ecosystem Priority Areas in South Africa: Maps to support sustainable development of water resources. WRC Report No. TT 500/11. Water Research Council, Pretoria. Ollis, D.J., Snaddon, C.D., Job, N.M. & Mboma, N. 2013. Classification System for Wetlands and other Aquatic Ecosystems in South Africa. User Manual: Inland Systems. SANBI Biodiversity Series 22. South African National Biodiversity Institute, Pretoria. Rountree, M.W., Malan, H. & Weston, B. (Editors). 2013. Manual for the Rapid Ecological Reserve Determination of inland wetlands (Version 2.0). Joint Department of Water Affairs/Water Research Commission study. Pretoria.

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