integrated watershed management: towards sustainable … · 2015. 4. 13. · integrated watershed...
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Integrated Watershed Management
Towards Sustainable Solutions in Africa
A. Bahri, H. Sally, R.E. Namara, M. McCartney,
S.B. Awulachew, B. van Koppen, and D. van Rooijen
International Water Management Institute
6th Biennial Rosenberg International Forum on Water Policy
June 23-27, 2008
Zaragoza, Spain
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OUTLINE
D LAND, WATER & LIVELIHOODS CHALLENGES IN
SUB-SAHARAN AFRICA
D INTEGRATED APPROACH TO WATERSHED
MANAGEMENT
D CASE STUDIES
D CONCLUSIONS AND POLICY IMPLICATIONS
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LAND, WATER & LIVELIHOODS CHALLENGES IN SUB-SAHARAN AFRICA
The percentage of the population living on less than $1 a
day
0
10
20
30
40
50
SSA SA EAP LAC ECA MNA
perc
en
tag
e
1990
1995
2001
SSA is the poorest region in the world – and getting poorer
(Source: NEPAD 2005, based on WB data)
GDP, Ag GDP and Population growth % 1980-2003
0
1
2
3
4
5
6
7
8
East Asia & Pacif ic Sout h Asia Middle East & Nor th
Af r ica
Lat in Amer ica &
Car ibbean
Sub-Saharan Afr ica
GDP grow th (annual %)
Ag value added (annual grow th %)
Population grow th %
Population growth in SSA has exceeded the growth
of both overall and agricultural GDP, so that
the population has become poorer
(Source: World Bank)
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Water storage mitigates variability
Low per capita storage (m3/capita)
6150
7,000
6,000
5,000
4,000
3,000
2,000
1,000
0
4 43
746 1287
1406 2
486
3255
4729
-Very little water
storage has been built in Africa. Increased storage could reduce poverty and improve health
Kenya
Eth
iop
ia
South
Afr
ica
Tha
iland
Lao
s
Chin
a
Bra
zil
Aust
ralia
Nort
hA
merica
World Bank (2003)
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Agricultural Water Management
D 3.8% water withdrawals for agriculture (3.6%), water
supply and energy.
D 183 million ha (Mha) (6%) of the total area under
cultivation:
D 97% of total cultivated area under rainfed. Over 90% of
the agricultural population dependent on green water.
D 21% (39.4 Mha) of total cultivated area potentially
irrigable. 9 Mha (5%) under water management. 7 Mha
under irrigation.
D Considerable scope for improved agricultural
production and food security through irrigation and
rainfed agriculture
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Transboundary River Basins in Africa Water resources management means transboundary management
•Very high water inter
dependence: 53 sovereign
states sharing 63
transboundary river basins
• Containing 93% of the total
water
• Covering 61% of the surface
area
• In which 77% of the human
population live
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Trends and challenges of integrated watershed management
1. Development and operation of water systems and structures, largely for irrigation.
2. Mid 1990s, water management placed into the context of river basins.
3. IWRM, IRBM, INRM, IWM, ICM, …:
D Holistic, integrated, and participatory approaches
D Based on hydrological and bio-geophysical units
D Link land and water development
D Link social and economic development with protection of natural ecosystems
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The Catchment Perspective
Return water flow
Virtual water flow
(Adapted from Falkenmark, 2002)
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CONCEPTUAL MODEL OF UPSTREAM-DOWNSTREAM INTERACTIONS (after Kirkby, In CPWF, 2003)
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Historical evolution of integrated watershed management in Africa
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Integrated watershed management in Africa
D Most African countries engaged in WM and in IWRM.
D Some have however moved to a state-wide approach.
D How much water should be allocated to agriculture, other uses, and for environmental uses still a subject of debate.
D There are major differences in countries’ needs and development stages: focus on how to attain the MDGs vs environmental protection and restoration.
D Most African international basin organizations ineffective (AfDB, 2007). Issues of treaties unresolved and national interests prevailing.
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CASE STUDIES
1. Balancing inter-sectoral water demands
in the Rufiji Basin in Tanzania
2. Water management in urban watersheds
3. The Nile – an example of multi-national
water management
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Great Ruaha River
Target flows in rivers and allowable
abstractions to meet Ruaha goal
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3)
The Problem: severe impacts on Ruaha National Park and failure of hydropower production
Area under rice (ha)
0
5000
10000
15000
20000
25000
30000
35000
40000
45000
1930 1940 1950 1960 1970 1980 1990 2000
Comparison of the dry season inflow to the Ihefu wetland and irrigated area
Since the mid-1990s, the Great in the Usangu catchment Ruaha River has ceased flowing in
180 1960
1970
1965 1990
1980 1985
1975
2000
y = -0.0029x + 153.75 1995
R2 = 0.7136 1999
the dry season every year because: 160
140 •water levels in the Usangu 120
wetland have dropped below a 100
80 critical level and outflows from the 60
40 wetland have ceased 20
•of diversions to rice irrigation 0
0 5,000 10,000 15,000 20,000 25,000 30,000 35,000 40,000 45,000 50,000 upstream of the wetland. Irrigated Area (ha)
Dry
season
Flo
w (M
m
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Value of water across sectors Should water be allocated to the highest economic benefits or to secure the livelihood of the poor?
Paddy irrigation Hydropower
Water consumed (Mm3) 542 1,094 (4,096)
Net Real Value ($m-3) 0.04 0.21 (0.06)
If based simply on criteria of economic efficiency, water would be allocated away from irrigation to the downstream hydropower schemes.
Rice:
D 14-24% national paddy production
D 60% exported out of basin
D 30,000 households ($ 912/year)
Hydropower:
D 50% of national power (284
MW)
D Only 1% rural population
connected
Ultimately, water allocation is a difficult political choice
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Wetland Hydrology
Wetland water levels P E
Storage Q
out
Qin
Water level at exit
NG’iriama exit
Great Ruaha
River
“Natural” annual water budget
Inflow: 3,390 Mm3
Rainfall: 490 Mm3
Evapotranspiration: 835 Mm3
Outflow: 3,045 Mm3
(78% of total input)
Human withdrawals from the rivers: 834 Mm
3
Environmental flow (Desktop Reserve
Annual environment flow: 635 Mm to
Model):
Mean annual flow: 2,933 Mm3
(93 m3 s
-1)
3
maintain the absolute basic ecological condition (21.6% of MAF)
Min dry season outflow: 0.5 m3s
-1
Min dry season inflow: 7.0 m3s
-1
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The African Urban Challenges
D World’s most rapid rate of urbanization (~ 5% / year)
D African urban population will nearly quadruple (138 million in 1990 - 500 million in 2020)
D Several large African cities share at least one international river basin: the Nile, Niger, Congo, Limpopo, Volta and Zambezi.
D Growing water demand and discharge of wastewater from the cities pose a special challenge for river basins’ water resources management.
D Water authorities manage their water supply, sewerage and stormwater drainage systems as separate entities.
D Sharing of common water bodies by several African cities poses a special threat to freshwater quality and aquatic ecosystems (ex: Lake Victoria).
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!( !( !(
!(
!(
Spatial context of urban water flows in Accra • Watershed Approach to
Urban WRM: manage both catchment (pollution control) and urban water cycle elements (water, wastewater, stormwater and water reuse) in an integrated way
Linking • Urban ~ Rural water management:
Agriculture ~ land treatment system and nutrient recycling part of the loop
• Domestic ~ Agricultural water use • Hydrologic Cycle /Water and
Nutrient Cycle
Volta Lake
Akosombo Dam
Kpong-Akuse Treatment Plant
Official urban boundary
Wejia Lake
Tanker waste Piped outflow Korle Lagoon disposal
Ocean
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Treatment Plant in Accra
Wastewater disposal into Ocean
at ‘Lavendel Hill’
Water production at Weija
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Wastewater reuse in Ghana
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Addis Ababa (after Awulachew, 2006)
• Access to sanitary facilities: 74% • <10% provided with sewer system • Kaliti WSP treats <3.6%
• 11 unions with 957 households and 7450 family members
• 262 ha cultivated by the unions, 134 ha by the private
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Water supply
Water reuse /disposal
(after van Rooijen)
Urban unit
Spatial context of urban water flows
• Water collection, storage, conveyance and treatment
• Flood protection
• Water supply, storage and distribution
• Sewage collection and treatment (MDG, EcoSan, etc.)
• (Waste)Water quantity & quality • Reuse for irrigation purposes and others
• Environmental services
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Trade-offs EEccoonnoommiicc vvaalluuee ooff wwaatteerr aanndd EEnnvviirroonnmmeennttaall aanndd ppuubblliicc
nnuuttrriieennttss hheeaalltthh rriisskkss
D Conserves water and reduces freshwater demand
D Health risks for the irrigators and D Provides a reliable water supply communities in contact with
to farmers wastewater
D Low-cost method for disposal of D Health risks for the consumers of municipal wastewater vegetables irrigated with wastewater
D Reduces pollution of rivers, D Contamination of groundwater canals and other surface waters
D Build-up of chemical pollutants in D Conserves nutrients, reducing the soil
the need for artificial fertilizers D Creation of habitats for disease
D Increases crop yields vectors in peri-urban areas
D Has direct positive income effect for farmers
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The Nile – an example of multi-national water management
D Unique in Africa for its long history, great technical complexity and its international scale.
D 15 bilateral treaties and agreements dated from 1891 to 1993 (Adams, 2001).
D The Nile Basin Initiative, established in 1999 with the support of the World Bank to facilitate cooperation among riparian countries.
D NBI’s Strategic Action Program: a basin wide Shared Vision Program and Subsidiary Action Programs (ENSAP, NELSAP)
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Economic value of cooperation: status quo versus full cooperation
Milli
on
US
D
10000
8000
6000
4000
2000
0
Ethiopia
Sudan
Egypt
Others
Total
Status quo Full cooperation
Extra benefits of full cooperation is US$4.94 billion annually (Whittington et al., 2005).
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Why multi-national water management is needed on the Blue Nile?
D Watershed degradation
D Flood damage along the Blue Nile in Sudan recently
estimated at USD 527 million for a 1-in-100-year flood
event (USD 52 million/year on average) (Cawood, 2005).
D Significant impacts of sedimentation:
D Loss of hydropower potential and of agricultural production
D Sediment load of the Blue Nile at El Diem of 140 million tons
per year (Ahmed, 2003)
D Management difficulties of irrigation canals networks in the
Gezira scheme: costs of the sediment clearance amounting
at more than 60% of the total O&M costs.
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The Blue Nile – an example of multi-national water management
D A research project, aiming at improving water and land management in the Ethiopian highlands and its impact on downstream stakeholders dependent on the Blue Nile is underway.
D The work includes:
D hydrological and water allocation modeling
D watershed management
D policy and institutional studies at various levels
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The Waters lems
hed Prob Causes
Impacts: Local
Impacts: DS
Sediment Volume and Content of Roseires Dam
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- 0.02
- 0.032
- 0.043
- 0.051
Lake Tana
3,809 3,920
Bosheilo
2,072 Welaka
4,798 Jemma
4,389
North Gojam
2,440 Muger
2,187
Guder
1,719
Finchaa
5,012
South Gojam
2,355 Anger
5,673
Didessa
3,874
Wonbera
Flow gauging station
Reservoir
6,246
Dabus
4,345
Beles
2,797 Dinder
1,102 Rahad
Khartoum
Border
Roseires
Sennar
Kessie
Outlet Lake Tana
Giwasi
Hawata
SUDAN
ETHIOPIA
4,345 Mean annual discharge (Mm3)
Schematic showing proposed configuration of the water allocation model of the Blue Nile
1.40E+03
1.20E+03
1.00E+03
8.00E+02
6.00E+02
4.00E+02
2.00E+02
0.00E+00
Runoff
Flow (cms)
6.00E+04
5.00E+04
4.00E+04
3.00E+04
2.00E+04
1.00E+04
0.00E+00
Sediment Export (t/ha)
hrus1
SYLDtha
Sediment Yield
hrus1
SURQ_GENmm
0
0.001
0.306
0.307
0.308
0.309
0 - 0.003
0.003000000
0.020000000
0.032000000
0.043000000
Modeling the Gumera watershed runoff Schematization of Blue Nile for and sediment yield, preliminary results erosion and sediment modeling
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CONCLUSIONS D IWM is about decision–making in a multiple-use and
multiple-user context to improve water productivity and derive optimum benefits for all relevant stakeholders.
D Different approaches are needed to address the critical development and management issues.
D Still a range of challenges:
D inter-sectoral competition for water
D dealing with trade-offs related to developmental and economic objectives, and equity and conservation considerations/between ecosystems
D integration across scales
D reconciling hydrological boundaries with administrative and political boundaries
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CONCLUSIONS D Decision-making can be enhanced using tools that
promote stakeholder dialogue and take into account existing local-level traditional arrangements.
D In urban watersheds, comprehensive understanding of the entire urban water system is required. Innovations and investment interventions in technological, institutional change and sociological learning are needed.
D Transboundary coordination is needed to foster major win-win opportunities and overcome constraints to upscaling promising management practices and technologies.
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POLICY IMPLICATIONS D The adoption of the ecosystem approach will ensure watershed
wide perspectives to development and management and make for social equity.
D The MUS concept in IWDM may provide the most equitable option on which watershed-wide plans may be based.
D Think more in terms of AWM rather than about irrigated or rainfed agriculture.
D Manage water, wastewater, non-point source pollution, and water reuse in an integrated way.
D In water allocation decisions, consideration of equity, food security, poverty reduction and development needs should be taken into account.
D Both watershed and administrative or social/cultural boundaries need to be considered.
D Nested institutional structures should be set up to manage us-ds interactions.
D Include informal small-scale water users.
D Adoption of a pragmatic mix of new and existing management arrangements to improve services and reduce conflicts.