Rethinking water storage for climate change adaptation in sub saharan africa
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GTZ project. Rethinking water storage for climate change adaptation in Sub-Saharan Africa. Project overview. Objective Guidance on storage options that ensure optimal adaptation to CC-induced impacts on water availability in SSA Partners Duration and focus

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Rethinking water storage for climate change adaptation in Sub-Saharan Africa

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GTZ project

Rethinking water storage for climate change adaptation in Sub-Saharan Africa

Project overview


Guidance on storage options that ensure optimal adaptation to CC-induced impacts on water availability in SSA

PartnersDuration and focus

  • Arba Minch University (AMU), Ethiopia2008-2011, Nile and Volta

  • 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

    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 output

    Guidelines on how to build climate change into decision-making processes for the planning and management of agricultural water storage in sub-Saharan Africa

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 Storage Continuum

Project Output

Guidance on:

“ … options that ensure optimal adaptation to CC-induced impacts on water availability in SSA”

Targeted at institutions that evaluate, design and implement water resource development projects and investment programs

  • International development agencies

  • State bodies

  • Public and private funding agencies


Basin scale analyses

Evaluation of climate change impacts on storage at basin scale –effectiveness

Site level analyses

Understanding storage at the local (economic and socio-political aspects) – suitability

  • Evaluation framework

  • Metrics to determine:

  • The need for water storage

  • The effectiveness of different options

  • The suitability of different options


Basin scale analyses (Nile and Volta)

  • Climate - rainfall, temperature, evaporation

  • Historic climate

  • CC scenarios (downscaled to the basins)

Hydrological model (SWAT/SWIM)

  • Current and future storage plus water use in each basin

  • Evaluation of climate change impacts on storage at the basin scale


Flow at key locations (sub-catchments)

  • Water resource modeling (WEAP)

  • current water resource development

  • future water resource development


Water availability for irrigation/hydropower

Effectiveness of existing and planned storage

Climate Modeling

  • 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

CCLM output for the Nile (A1B scenario)


Mean Temperature (mm)




Annual Rainfall (mm)



CCLM output for the Volta (A1B scenario)


Mean Temperature (oC)




Annual Rainfall (mm)



RCM Scenarios – Rainfall (Nile)

2090s – 1990s

2030s – 1990s

Hydrological Modeling

  • Rainfall-Runoff simulation to determine impacts of CC on flow regimes and groundwater recharge

  • Daily simulation to deduce impacts on extremes – floods and droughts

Basin characteristics

Topographic WI


MWB: Model calibration and validation

Water Resource Modeling (WEAP)

  • Water Evaluation and Planning (WEAP) Model

  • Water accounting model (mass balance) – optimizes water use (monthly time-step)

  • Data from:


+ Planned development – feasibility studies conducted

* Potential development – identified in Master Plans etc.

WEAP configuration for the Volta

Current situation

Devaraj de Condappa et al (2008)

WEAP configuration for the Nile

Current situation

Near future

Distant future

Blue Nile Ethiopia:

Existing and Planned schemes

Results (no climate change)

Site Level Analyses

  • 3 locations in each of Nile and Volta

  • Nile = Koga, Gumera , GuderIdris

  • Volta = Vea (Yaragatna River), Golinga, Sata

  • Evaluation of socio-economic aspects of storage

    • What benefits accrue and who gets the benefits?

    • What are the costs and who has to pay?

  • Issues

    • availability; economic viability; uptake; access; equity; institutional arrangements; socio-political aspects etc.

  • Approach

    Socio-economic survey – Quantitative

    • Conducted in all sub-basins

    • Information on benefits/costs people derive from different water storage options as well as perceptions of CC

      ZEF investigations – Qualitative

    • Gender aspects and the access to natural resources in a small-scale irrigation scheme (Shina dam), Gumara watershed.

    • Watershed and irrigation management in a large-scale irrigation scheme, Koga watershed.

    • Resettlement, social bonds and attachment to land in a large-scale irrigation scheme, Koga watershed.

    • Power relations and control over water resources. The case of Indris irrigation scheme.

    • Access to land and water management: Indris irrigation scheme.

    • Socio-economic and political impact of water storage facilities on rural household livelihood. A study of Gumera watershed, Abay River Basin, Ethiopia

    Impacts of small-scale water storage on rural household livelihoods in Gumera


    • 3 crops/year – sufficient food

    • Increased variety of crops (e.g. rice)

    • Increased income. Farmers can earn between 3,000 – 5,000 EB per vegetable garden

    • Increased size of land holdings. Some farmers can now rent land to expand their production

    • Reduced cases of water borne diseases

    • Stronger relationship with neighbors due to water sharing


    • Cracking of the soil

    • High material and construction costs

    • Labor shortage – common with FHHs, old age HHs

    • Limited skills in management of ponds

    Evaluation Framework

    Objective of water storage is to reduce climate vulnerability

    Increased adaptive capacity

    Present climate vulnerability


    Water storage (adaptation strategy)

    Increased availability and access to water

    Increased agricultural productivity

    Future climate vulnerability

    (post adaptation)

    Increased water security

    Future climate vulnerability < Present climate vulnerability


    No (stop evaluation)

    Is storage needed now and/or will it be in future?

    No (stop evaluation)

    Is it and will it in future be technically effective?


    No (stop evaluation)

    Is it and will it in future be socio-economically suitable?


    Continue with detailed planning


    • 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

    The need for agricultural water storage

    Technical effectiveness of the water storage system

    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


    Suitability of the water storage system

    Most likely metrics through multi-criteria scoring systems rather than numerical data

    Capacity Building

    Capacity Building:

    • 3 MSc’s completed (Arba-Minch)

    • 12 Masters ongoing:

      • Arba Minch

      • ZEF

      • University of Accra

      • Humboldt University

    • 1 PhD student University of Berlin

    Project website


    Photo Gallery

    Links to other sites

    Reports/Power points/Papers


    Bias correction

    For each grid point, long-term (1961-90) observation (corrected) and long-term simulation by CCLM are compared on a monthly basis;

    The bias per month is calculated for each cell and month;

    The climate projections are corrected by this bias.

    Simulated by climate model

    Simulated and bias corrected

    Observation corrected by measurement error


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