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

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Food security in Africa is likely to be “severely compromised” by climate change with production halved by 2020 …

Food security in Africa is likely to be “severely compromised” by climate change with production halved by 2020

> 95% of Africa’s agriculture currently depends on rainfall

Changes in hydrology will aggravate other stresses and threaten sustainable development

As a consequence of climate change:

80,000 km2 “constrained” will improve

600,000 km2 currently “moderately constrained” will become “severely limited”

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  • 1. GTZ project Rethinking water storage for climate change adaptation in Sub-Saharan Africa
  • 2. Background • Food security in Africa is likely to be “severely compromised” by climate change with production halved by 2020 • > 95% of Africa’s agriculture currently depends on rainfall • Changes in hydrology will aggravate other stresses and threaten sustainable development • As a consequence of climate change: • 80,000 km2 “constrained” will improve • 600,000 km2 currently “moderately constrained” will become “severely limited”
  • 3. Adaptation: More storage required
  • 4. More storage required (?) Type of storage and how it is used is important
  • 5. Range of storage options
  • 6. Project Purpose Guidance on: “ …..storage options that ensure optimal adaptation to climate change induced impacts on water availability in SSA” • How do we determine storage needs (now and in the future) ? needs assessment • How do we choose between different storage options? options assessment
  • 7. Adaptation Strategies
  • 8. Physical Storage Continuum
  • 9. Research questions • How is climate change likely to affect future water demand ? e.g. Irrigation demand under different conditions of rainfall, temperature and evaporation • How is climate change likely to affect water availability and what are the implications for different types of storage? e.g. river yields, groundwater recharge, runoff, evaporation from storage • How is climate change likely to affect “externalities” of different storage types? e.g. Public health impacts (e.g. malaria, schistosomiasis) Environmental impacts (e.g. runoff, river flows) • How do we build climate change change into decision making process for storage?
  • 10. Method (1) 1) Determine evaluation criteria Criteria Technical Social Economic Environmental Reliability Resilience Sustainability Vulnerability As far as possible: • Objective /quantitative • Applicable to different storage types • Applicable across a range of scales • Applicable now and under climate change scenarios
  • 11. Method (2) 2) Basin scale anlaysis (Nile and Volta) • Evaluation of climate change impacts on storage at basin scale Activity Method Determine impact of climate Rainfall, Downscaling of GCM data change on climate in each temperature, basin PE Determine impact of climate g/w recharge Downscaled GCM data + cc change on basin hydrology Runoff scenarios, through (2 scenarios) – A2 and B2 Flow hydrological model (SWAT, STRM) Evaluate impact of climate Large scale irrigation For each scenario, change on existing and Hydropower hydrology modified by cc planned water storage Well fields applied to water resource model (WEAP) Evaluate consequences For each scenario assess in terms of evaluation criteria
  • 12. Method (3) 3) Site level analyses (locations in each of Nile and Volta) • Evaluation of climate change impacts on different storage types Activity Method Evaluate -Water stored and how its Surveys, site investigations suitability/effectiveness of used to obtain information for the different storage types -Economic performance evaluation criteria under current conditions -Livelihood impacts (Access, Equity) Evaluate -Water stored and how its Downscaled cc to evaluate suitability/effectiveness of used biophysical implications of different storage types -Economic performance different scenarios under climate change -Livelihood impacts Likely implications based on conditions (Access, Equity) evaluation criteria
  • 13. Method (4) 4) Develop Guidance • Draw together lessons learned into guidance on introducing climate change into decision-making processes for storage
  • 14. Project Progress • Inception workshop (April 2008) • Project website established – http://africastorage-cc.iwmi.org/Default.aspx • 3 case study sites selected in Ghana (site visits undertaken) • 3 possible sites identified in Ethiopia (field trip just completed) • Baseline reviews of existing storage in Volta and Nile • Report on acquisition of storage in the Nile • Notes on current plans for future storage in the Nile and Volta • 1 MSc student (Homboldt University) started in Volta • 3 MSc students (Arba Minch University) started in the Nile • 1 PhD student (Frei University) started in the Nile
  • 15. Volta: Inventory Boreholes > 6,000 Large dams Total reservoir storage: 165 Bm3 (4 x MAR) Formal irrigation: 10,000 ha Small dams in Northern Ghana Potential irrigation: 346,000 ha
  • 16. Ethiopian Blue Nile Inventory Nile: Inventory Potential Irrigation Hand dug wells – Amhara Region Potential Dam locations Total reservoir storage: 11.5 Bm3 ( 0.25 x MAR at Sudan border) Formal irrigation: 10,000 ha Potential irrigation: 800,000 ha
  • 17. Water Resource Development in the Ethiopian Blue Nile Irrigation upstream of Lake Tana 7,200 ha Lake Tana Outlet Lake Tana Tis Abbay Beles hydropower Bosheilo SUDAN Border Welaka North Gojam South Gojam Jemma ETHIOPIA Wonbera Muger Irrigation upstream of Lake Tana 69,053ha Dabus Finchaa Irrigation Diversions 8,145 ha Lake Tana Pumping from Reservoir 2,424 Lake Tana 5,000ha Guder Beles Didessa Irrigation scheme Finchaa Outlet Lake Tana Upper Beles 53,700 ha Upper Dinder 10,000 ha Bosheilo Border Welaka Lower Beles North Gojam Current 85,000 ha South Gojam Jemma ETHIOPIA Wonbera Karadobi Muger Irrigation upstream of Lake Tana 69,053 ha Dabus Anger Lake Tana NW Lake Tana Finchaa Pumping 6,720ha Irrigation Diversions 20,145 ha 2,424 Anger 14,450 ha Reservoir Outlet Lake Tana Didessa 14,670ha Guder Upper Dinder 10,000 ha Beles Didessa Irrigation scheme Bosheilo Finchaa Border SUDAN Welaka Upper Beles 53,700 ha 2015 ETHIOPIA Lower Beles 85,000 ha South Gojam North Gojam Jemma Wonbera Lower Beko Abo Dabus Mendaya Karadobi Muger Upper Lower Dabus Nekemte 11,220ha Dabus 9,661ha Didessa Anger Finchaa & Neshe Guder Diversions Dabus Didessa 27,217 ha 4,896 ha Anger irrigation 14,450 ha Reservoir 53,668 ha Irrigation scheme Finchaa Didessa 14,670ha Guder diversion 4,100ha Didessa Guder 2025
  • 18. Water Resources plans for the Ethiopian Blue Nile Current 2015 2025 Irrigation (ha) 10,000 210,000 390,000 Hydropower (MW) 218 2,194 6,500 Large Dam Storage 11.5 56.8 ~100 (Bm3) Impact on flow with no climate change (Bm3): Natural Current 2015 Outlet Lake Tana 3.9 4.0 0.9 Kessie 14.9 14.9 11.9 Border with Sudan 45.7 45.6 43.5
  • 19. climate change Impacts Climate in the Volta and Nile: Already experience high variability • Likely consequence of climate change: • Warmer temperatures, more extreme temperatures • Greater variability, more floods/droughts • Higher evaporation and transpiration • Lower confidence: • Direction and magnitude of rainfall changes • Changes in extremes (frequency/intensity)
  • 20. Scenarios – to be downscaled to basins and sites Simulation results of the dynamical regional model REMO – scenario (2001-2050 vs 1960-2000).
  • 21. Three Conclusions 1) Water storage is the key to climate change adaptation for agriculture in Africa 2) climate change will affect the function and operation of different storage types, differently 3) Important to assess the effectiveness and suitability of different storage types under uncertain conditions of climate change Need to Rethink water storage options for climate change adaptation
  • 22. Thanks