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Rethinking water storage for agricultural adaptation to climate change in Sub-
Sahara AfricaDr. Matthew McCartney and Dr. Irit Eguavoen
Tropentag Zürich, 16. September 2010
Research funded by:
• Project• Project rationale – water storage as adaptation to CC• Water Storage Continuum• Approach• Research results – example Koga watershed• Project output – evaluation metrics
Project 2008-2011
Objective Guidance on storage options that ensure optimal adaptation to CC-induced impacts on water
availability in SSA
Research Questions• How can the need for water storage and the effectiveness and suitability of different
storage options be evaluated and compared for different climate scenarios? • How can water resource planning and management processes be modified to better
account for the uncertainties arising from climate change?
Principal outputGuidelines on how to build climate change into decision-making processes for the planning
and management of agricultural water storage in sub-Saharan Africa
Project 2008-2011
Partners• Arba Minch University (AMU), Ethiopia• Ethiopian Economic Association (EEA)• Water Research Institute (WRI), Ghana• Institute of Statistical, Social and Economic Research (ISSER), Ghana • Center for Development Research (ZEF), Germany • Potsdam Institute for Climate Impact Research (PIK), Germany
Blue Nile River basin/ Ethiopia
Volta River basin/ Ghana
Project Rationale
• Water storage is widely advocated as a key mechanism for CC adaptation• Little analysis of how CC affects existing water storage or how to account for CC in the
planning and management of new water storage
Physical Water Storage Continuum
Conceptual overview developed by project participants (IWMI Policy Brief 31)
Basin scale analysesEvaluation of climate change impacts on storage at basin scale
► effectiveness
Site level analysesUnderstanding storage at the local (hydrological, economic, socio-political aspects) ► need, effectiveness & suitability
Project Approach
Evaluation metrics to determine• The need for water storage• The effectiveness of different options • The suitability of different options
Blue Nile basin watershedsKoga – Gumara – Indris
Volta basin watershedsVea (Yaragagna) – Saata – Golinga
Climate - rainfall, temperature, evaporation • Historic climate • CC scenarios (downscaled to the basins)
Hydrological model (SWAT/ SWIM)
Results:Flow at key locations (sub-catchments)
Water resource modeling (WEAP)• current water resource development • future water resource development
Results:Water availability for irrigation/hydropower Effectiveness of existing and planned storage
Basin scale analyses (Blue Nile and Volta)
• Current and future storage plus water use in each basin
• Evaluation of climate change impacts on storage at the basin scale
• Analysis of sub-catchments/ watersheds
PROJECT
PERIOD
Climate Modeling (Blue Nile and Volta)
• Approaches of downscaling – Dynamical climate models: CCLM and REMO (both for A1B) + bias correction – Statistical climate model: WettReg (for different scenarios and GCMs)
• Resolution: 0.5° (attempt 10 km but not yet complete)• Further regionalization / interpolation to locations of interest
Mean annual total precipitation (mm) 1971-2000
Source: Hattermann 2010
Hydrological Modeling (sub-catchments)
• Rainfall-Runoff simulation to determine impacts of CC on flow regimes and groundwater recharge
• Daily simulation to deduce impacts on extremes – floods and droughts
Blue Nile – Models
STREAM Resolution 1km,
SWIM Soil Water Model (root zone and deep soil water)
Modified MWB Three parameter lumped model – gridded 10km
Volta – Models
SWAT Soil and Water Assessment Tool – Hydrological Response Units
Water Resource Modeling
• Water Evaluation and Planning (WEAP) Model at basin level/ of selected sub-catchments
• Water accounting model (mass balance) – optimizes water use (monthly time-step)
Blue Nile basin Volta basin
MoWR Hydrological Services Department
Basin Master Plans Volta River Authority
Irrigation efficiency studies Ghana Water Resources Management Study
New scheme feasibility studies
Sources of data
Site Level Analyses/ Ethiopia
Indris
Ethnographic research• acquisition of storage facilities• rules & regulations• land & water rights• management bodies• resettlement & compensation• livelihood change• gender aspects
Socio-economic surveys• 200 hh per watershed• identification of water sources• cost & benefits of water storage• farmers´ perception of storageand climate change(data analysis on-going)
Source: ZEF
Research results – Blue Nile basin
Current Near future Distant future
Irrigation (ha) 10,000 210,000 451,000
Hydropower (MW) 218 2,194 6,426
Storage (Bm3) 11.5 56.8 ~100
0
5,000
10,000
15,000
20,000
25,000
30,000
Jan‐60
Jul‐61
Jan‐63
Jul‐64
Jan‐66
Jul‐67
Jan‐69
Jul‐70
Jan‐72
Jul‐73
Jan‐75
Jul‐76
Jan‐78
Jul‐79
Jan‐81
Jul‐82
Jan‐84
Jul‐85
Jan‐87
Jul‐88
Jan‐90
Jul‐91
Flow (Mm3)
Simulated natural and 2025 scenario flow at the border
Simulated natural flow at the border
Simulated 2025 scenario flow at the border
0
2,000
4,000
6,000
8,000
10,000
12,000
14,000
16,000
18,000
1 2 3 4 5 6 7 8 9 10 11 12
Mean Mon
thly Flow (Mm
3 )
Natural flow 2015 flow 2025 flow
Simulated natural MAF = 47.0 Bm3
Simulated currentMAF = 46.9 Bm3
Simulated 2015 MAF = 44.8 Bm3
Simulated 2025 MAF = 44.4 Bm3
Results (no climate change)
Current Near future
Distant future
Irrigation Demand (Bm3) 0.20 3.65 5.13
Hydropower (Gwhy-1) 1,383 12,908 31,297
Blue Nile/ EthiopiaExisting and planned schemes
Sources: Mc Cartney et al. 2009
Water Resource Modeling
Lake Tana
Regulated flows Unregulated flows (downstream of proposed dams and unregulated rivers)
Lake pumping schemes
246
1925
Abay (Blue Nile)
Tis IssatFallsTis Abay
power plants
116Koga
Gilgel AbayMegech
Gondar town
Ribb Gumara
Intermediate flow
Beles hydropowertransfer
Legend Irrigation Scheme
116 Mean annual inflow (Mm3)
270Andassa
DamWithdrawalsReturn flow
176 216 244
Rivers
2180WEAP model set up forLake Tana sub-basin
1783
1784
1785
1786
1787
1788
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35
Lake
leve
l (m
asl)
YearNatural FDS with TBF FDS with VEF
Source: McCartney et al. 2010
Research results – Koga watershed
Evaluating the technical Performance of the Koga and Gomit reservoirs in the Blue Nile under Existing Conditions and Possible Climate change
Fuad Abdo Yassin & Matthew McCartney
Reliability Resilience Vulnerability
Koga Gomit Koga Gomit Koga Gomit
Historic climate 0.992 0.950 0.037 0.032 37 71
-20% rainfall 0.968 0.874 0.020 0.016 64 88
+20% rainfall 1.000 0.979 1.000 0.055 0 44
Metrics Indicators
Reliability • the probability that the system is in a satisfactory state (i.e. can meet demands).
Resilience • the capability of the system to return to a satisfactory state from a state of failure
Vulnerability • the maximum duration and the cumulative maximum extent of system failure
RRV for Koga and Gomit dams in the Nile Basin:
Challenge = need to be able to compute these metrics for a number of storage types within a storage system
Research results – Koga watershed
Tropentag 2010 poster session: water management
Evaluating the technical Performance of the Koga and Gomit reservoirs in the Blue Nile under Existing Conditions and Possible Climate change
Fuad Abdo Yassin & Matthew McCartney
Institutional and organizational aspects of irrigation management
• Pilot project for farmer-based management - runs at risk to fail • Re-organization of farmers in groups – unclear formal/ legal status• Training and involvement of farmers – not sufficient• Livelihood changes through irrigation agriculture – unexpected workload• Conflicts with Christian orthodox authorities – holidays and religious duties
How Winners become losers. Relocatees re-establishment of livelihood.
• Delay in land allocation - long period of non-farming• 400 households were relocated to close town• Irregularities in compensation payments• Change of livelihood - giving up livestock rearing/ urban activities• Process of urbanisation, integration in small town settlement• Problems with land for houses• Importance of social networks• New sources of vulnerability (e.g. HIV/ AIDS)
Research results – Koga dam & irrigation
Sources: Tesfai 2010, Marx 2010
Project output - evaluation metrics
Evaluation metrics should be as far as possible:
• Objective /quantitative• The same for all storage types • Applicable across a range of scales• Applicable now and under climate change scenarios• Transparent in its evaluation approach• Easy to use by advisers and policy makers• Illustrate policy options• Include veto/ exit options, if needed
► score-based approach, possible to visualize
Evaluation metrics to determine• The need for water storage• The effectiveness of different options • The suitability of different options
technical economic
socio-economic
social
environ-mental
Need/ effectiveness Suitability
Social evaluation criteria
1. Accessibility2a. Social cost2b. Social benefits3. Management/ Maintenance4. Options to Adapt
technical economic
socio-economic
social
environ-mental
Project output - evaluation metrics
2a. Social cost - Measures the social cost of the storage system.
Topics: relocation/ compensation, social stratification, social and patronage networks, bargaining power, conflict, health
The lower the social cost the greater the social value of the storage system.
Metrics to determine
• The suitability of different options
Water storage needed? YES.
Water storage effective? YES.
Metrics to determine• The need for water storage• The effectiveness of different options
Social cost scores (emic perspective)
Class Description Score
No social cost The potential beneficiaries of the location where the storage facility is situated do not report on social cost.
4
Low social cost The potential beneficiaries of the location where the storage facility is situated report on minor social cost but indicate that it is definitely worth taking this cost to enjoy the economic water storage benefits.
3
High social cost
The potential beneficiaries of the location where the storage facility is situated report on high social cost but indicate that it is still worth taking this cost to enjoy the economic water storage benefits.
2
Very high social cost
The potential beneficiaries of the location where the storage facility is situated report on very high social cost and are unsure whether taking this cost is outweighed by the economic water storage benefits.
1
Unacceptable social cost
The potential beneficiaries of the location where the storage facility is situated report on very high social cost which cannot be outweighed by the economic water storage benefits.
Veto
Does the project entail high social costs? ► No (score 4-3). ► Considerably high (score 2) ► Continue► Yes (score 1 - veto) ► Stop because not suitable.
Thank you.
Project leadership:
Dr. Matthew McCartneyIWMI East African regional office Addis [email protected]
IWMI project homepage:http://africastorage-cc.iwmi.org/Default.aspx
ZEF project homepage:http://www.zef.de/1393.html
References• Eguavoen, I. (2009) The aquisition of water storage facilities in the Abay River basin, Ethiopia.
ZEF Working Paper 38.• Hattermann, Fred (March 2010). Regional climate scenarios for the Blue Nile and Volta. PIK
presentation.• IWMI (2009) Flexible Water Storage Options and Adaptation to Climate Change. Policy Brief 31• Johnston, R.& McCartney M. (2010) Inventory of Water Storage Options in the Blue Nile and Volta
River basins. IWMI Working Paper 140.• Marx, S. (2010) Chances and Obstacles in Implementing a large-scale Irrigation Scheme
managed by Farmers: Koga Irrigation and Watershed Management Project. Field research report. Bonn. ZEF.
• McCartney, M.P., Ibrahim, Y., Seleshi, Y. & Awulachew, S.B. (2009) Application of the Water Evaluation and Planning Model (WEAP) to simulate current and future water demand in the Blue Nile. In: Awulachew, S.B., Erkossa,T., Smakhtin, V. & Fernando, A. (Eds) Improved water and land management in the Ethiopian Highlands: Its impact on downstream stakeholders dependent on the Blue Nile: Intermediate Results Dissemination Workshop 5-6 February, 2009. Addis Ababa, Ethiopia. 78-88.
• McCartney, M.P., Alemayehu, T., Shiferaw, A. & Awulachew, S. B. (2010) Evaluation of current and future water resources development in the Lake Tana Basin, Ethiopia. Colombo, Sri Lanka: International Water Management Institute. Colombo, Sri Lanka: International Water Management Institute. IWMI Research Report 134.
• Tesfai, W. (2010) Relocatees re-establishment of livelihood in the Koga irrigations project, Amhara Region, Ethiopia. Field research report. Bonn. ZEF.