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

Koga site

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 Ababam.mccartney@cgiar.org

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.