cities and water: sinks or sponges?

Cities and Water:Sinks or Sponges?

16th International River SymposiumBrisbane, 23 September 2013

Jeremy Bird International Water Management Institute

• More than half of the world’s population lives in urban areas.

• Urban growth is most rapid in developing countries: cities gain an average of 5 million residents each month.

• There are 23 megacities, compared to 2 in 1970. By 2025, there will be 37.

Percentage of urban population and agglomerations by size class, 2011

Percentage of urban population and agglomerations by size class, 2025

Source: United Nations, Department of Economic and Social Affairs, Population Division: World Urbanization Prospects, the 2011 Revision. New York 2012

What is urban? What is rural?

Accra: the administrative boundary is outpaced by urban sprawl

Map of population density

South Asia exemplifies urbanization challenges and rural-urban tensions

http://pricetags.files.wordpress.com/2013/03/pop-density.jpg

Example: New Delhi

1974 1999 2013

Time for a new approach….

“For most of the last century, economic growth was fuelled by

what seemed to be a certain truth: the abundance of natural

resources. We mined our way to growth. We burned our way to

prosperity. We believed in consumption without consequences.

Those days are gone….. Over time, that model is a recipe for

national disaster. It is a global suicide pact.”

United Nations Secretary General Ban Ki-Moon,

World Economic Forum 29th January 2012.

Urban unit

• Supply infrastructure • Sewage infrastructure

Wastewater disposal

• Receiving water bodies• Use in irrigated agriculture

Water source• River

• Groundwater• Reservoir

• Rainfall

wastewater treatment?

Sink and Sponge

Source: van Rooijen, D.J.; Biggs, T.W.; Smout, I.; Drechsel, P. 2010. Urban growth, wastewater production and use in irrigated agriculture: A comparative study of Accra, Addis Ababa and Hyderabad. Irrigation and Drainage Systems 24(1-2): 53-64

Urban expansion, Hyderabad, India

Source: Wikimedia Commons

Pulling water in from an increasing distance Hyderabad, India

Krishna River

Himayat Sagar

Osman Sagar

GW

Musi River

GW – Ground WaterNJS – Nagarjuna Sagar reservoir

HyderabadWaste water irrigation

industry

Godavari Basin

Krishna Basin

NJS

Basin Border

Musi River

P ET

Manjira

Singur

Godavari River water

Water pum

ped

Water pum

ped

Source: van Rooijen, D.; Turral, H.; Biggs, T.W. 2005. Sponge city: Water balance of mega-city water use and wastewater use in Hyderabad, India. Irrigation and Drainage 54: 81-91.

Change in water sources to satisfy urban needs

Hyderabad Water Supplies and Demands

Osman Sagar Himayat SagarGround Water

Singur

Manjira

Krishna river

Godavari

extra needed (demand - total supply)

0

10

20

30

40

50

60

70

80

90

100

1950

1955

1960

1965

1970

1975

1980

1985

1990

1995

2000

2005

2010

2015

2020

2025

2030

time (years)

Mill

ion

Cu

bic

Me

ters

pe

r M

on

th

Source: Van Rooijen et al., 2005

Informal water markets on the increase

• No Indian city has a 24/7 water supply.

• Demand for tanker supply on the increase.

• Most affected are peri-urban areas where groundwater tables are dropping.

Photo by Akshay Davis

Groundwater extraction in

India: Urban needs add to existing stress from agricultural

use

Examples of water transfers exist

…as allocation to agriculture reduced and transferred to urban use

Agricultural production levels maintained…

Reflections : Cities as a water sink• Footprint of urban expansion on water for irrigation can be extensive

- depends on water source (surface water – groundwater; basin diversion, etc.) and response measures to incentivize water productivity gains – cities like Chennai and examples from China show a major impact on

peri-urban water needs.

• Rapidly urbanizing cities need a shift to more pro-active, cross-sectoral planning capacity, e.g:– a broad multi-sector approach: managing water transfers, demand

management, rainwater harvesting, conjunctive use, etc.– explore downstream irrigation opportunities from a more continuous

supply of wastewater and increased storm runoff– promote health safeguards for wastewater re-use

What happens to the urban ‘return’ flow?

Urban unit

Wastewater disposal

Water source

wastewater treatment?

In most cities in sub-Saharan Africa, S. Asia and SE Asia, population growth has outpaced the development of sanitation infrastructure, making the management of urban waste, human excreta and wastewater ineffective.

Sewer networks collect only a tiny fraction of city wastewater.

The few wastewater treatment plants that exist are often

overloaded.

This leads to severe water pollution in peri-urban areas

Wastewater

Piped water

Also an opportunity?

Due to the proximity of markets and lack of refrigerated transport and storage, a whole irrigation sub-sector specialized in perishable exotic vegetables is emerging in and around growing cities.

In the economically important rural–urban interface, it is difficult to find a reliable unpolluted water

source.

0

5

10

15

20

25

30

Dilutedwastewateror polluted

water

Untreatedwastewater

Groundwater Treatedwastewater

River Othersurface

water bodies

Rainfed Irrigationcanal

Opendrainage

Num

ber o

f citi

es

Source: IWMI, RR 127

Global survey of irrigation source in urban and peri-urban areas:

In and around three of four cities in the developing world, farmers use polluted irrigation water for the production of high-value crops

Water quality improves over 40 km along the Musi River

Hyderabad

Sources: IWMI/J. Ensink

IWMI works closely with WHO and FAO on safe wastewater reuse

• Assessing the extent of reuse, risks and benefits.• Developing and testing low-cost options for microbial risk reduction

(multi-barrier approach from farm to fork).• Supporting international guidelines and capacity building.

• health risk mitigation measures have a RoI of U$4.9 for each dollar invested.

Mitigating risks where wastewater treatment remains a challenge

Australia: National target of 30% of wastewater being recycled by 2015

%

Source: Marsden Jacob Associates 2012

Reflections II : Cities as sponges

• Wastewater reuse can minimize risks of urban areas becoming water sinks and contribute to water needs at basin scale.

• Treatment important: 80% of the contamination of India’s surface water is due to the lack of treatment facilities.

• Where conventional treatment remains limited, pathogenic risks can be controlled through safer irrigation practices.

• Reducing nutrient loss is becoming a major environmental driver of change

Urban food demands and waste generation mirror the same challenges

Source: Wikimedia Commons

Source: IWMI

!?

Import/Export

Livestock

FoodFood crops and fodder plants

Soil nutrients

Organic solid waste, sludge & wastewater

Controlled and un-controlled disposal

Fertilizer

Urban pollution and nutrient wasting

Peri-urban and rural nutrient mining

Production

Consumption/Processing

Cities = vast nutrient sinks

Challenge:Closing the

nutrient loop

Closing the loop is no easy endeavor in the rural-urban context

Technical solutions for resource recovery are available, but:

• transport costs are high,

• too dependent on public subsidies,

• projects rarely survive their pilot periods, and

• big gaps in business thinking.

Resource Recovery & Reuse (RRR)A research flagship of CGIAR-WLE using a business approach to

attract private capital

Old challenges require new thinking

New understandings required to close the loop

RRR program for water, nutrient and energy recovery from domestic and agro-industrial waste

Database of 150+ inspiring RRR business cases Selection of 60 cases for in-depth analysis (see map) So far 20 promising business models extracted Feasibility studies of models starting in 9 cities Business model implementation targeting 5 cities

Example of a business model currently being implemented in Ghana as a Public-Private Partnership:

Fecal Sludge Valorization(returning nutrients and reducing pollution)

Other options combine biogas and nutrient recovery

Introducing business models to turn waste into an asset

• Solid waste and fecal sludge

composting in Asia and Africa

could save billions of US$ per

year, assuming a market for only

25% of the urban organic waste.

• Not a new concept, but many

pilots not viable or sustainable

• Business models for resource

recovery & reuse (RRR) target

private and public investors and

business schools.

Some ‘nexus’ implications

Energy reduction in • Water treatment• Chemical fertilizer

production and transport

Environmental benefits• Reduced pollution of

water bodies• Reduced nitrogen and

phosphorous demand • Reduced GHG emissions

Addressing water challenges of rapid urbanization

• Analysis: expand inter-sectoral perspective at basin scale to include nutrient and carbon emission considerations.

• Peri-urban areas: responsive research, policy and development focus required to reflect the rapid pace of urban transformation

• Urban management: support to closed loop processes to avoid cities becoming sinks for valuable resources.

• Agriculture-sanitation interface: exploit new approaches, win-win solutions and incentive mechanisms.

• Agriculture water productivity: innovations needed to release freshwater for other sectors needs – who pays?

www.iwmi.org/Topics/RRR http://wle.cgiar.org/RRR

Closing the loop