A Water Allocation System for the Volta Basin: The impact of agricultural and hydropower development on the water resources of the basin. Constanze Leemhuis, Barnabas Amisigo, Gerlinde Jung, Wilson Agyei Agyare, Raymond Kasei, Tyler Frazier, Benjamin Kofi Nyarko, Nicos Perez, Anik Bhaduri, Jens Liebe Climate, Land Use, Hydrology Economics, Institutions, Stakeholders Field Investigations Processes of decision making and information flows Land Conversion Remote Sensing Institutional Analysis Instrumentation Water Supply Mesoscale Climate Hydrology Institutional Analysis Integrated Basin Model OUTLINE •Agricultural and hydropower development •The Volta Basin Water Allocation System (VB-WAS) •Climate and Reservoir Scenarios •Small and medium reservoir development •Large reservoir development: The Bui Case •Real time operational Water Management AGRICULTURAL AND HYDROPOWER DEVELOPMENT Ziga Reservoir NIGER Volume: 0.2 km³ 2000 Lery Reservoir MALI Volume: 0.6 km³ 1976 B U R K I N A F A S Bagre Reservoir Volume: 1.7 km³ 1992 O BURKINA FASO Small Reservoirs Volume: 0.6 km³ Kompienga Reservoir Volume: 2.0 km³ 1984 Tono Reservoir Volume: 0.1 km³ 1980 BENIN Bui Reservoir Volume: 12.3 km³ IVORY COAST 2009/2010 lake TOGO Volta Lake Volta Volume: 148 km³ 1964 GHANA Small Reservoirs Volume: 0.1 km³ G H A N A Kpong Reservoir Volume: 0.2 km³ 1982 AGRICULTURAL AND HYDROPOWER DEVELOPMENT •Climate variabilty has an impact on agricultural and hydropower development and management in the Volta basin. •In the 80s of the last century a series of spatial significant drought years severly hit the socio-economy of the Volta basin. 1982 1983 m n m n n m n m m n n m n mm n n m m n m n m n n m m n m n m n m n m n n m n m m n n m n mm n n m m n m n m n n m m mn n m n n m m n n m m n mn n m n mm n mn n mn n m mn m n m m m n n m mn n m n m n n n m m m n m n m n m n m n m n mn n m n m m n m n n m m m n n mn n n m m n n m m mn n m n m n m n m m m n m n n n m m n m n m n m n m n n m n m m n m n m n 1984 n m m n m n m n m n m n m n n m n m m n n m n mm n n m m n m n m n n m m mn n m n n m m n n m m n mn n m n mm n mn n mn n m mn m n m m m n n m mn n m n m n n n m m m n m n m m n n m n m n mn n m n m m n m n m n m m n n mn n n m m n n m m mn n m n m n m n m m m n m n n n m m n m n m n m n m n n m n m m n m n n m m n m n n m m n m n m n n m m mn n m n n m m n n m m n m n m n m mn n m n mn n mn n m mn m n m m m n n m n m n m n m n n n m m m n m n m mn n m n m n mn n m n m m n m n m n m m n n mn n n m m n n m m mn n m n m n m n m m m n m n n m n m n m n m n m n m n n m n m m n m n n m m n m n n m m n m n m n m n m n m n m n m n m n m n m m n n n m m n m n m n m n m n m n m n m n m n m n n m n m n m n n m m n mn n mn m m m n m n m n mn n m n n m m n m m n m n n m m mn m n mn n mn n mn mn mn n m m n n m n mn mm mn m n m n mn n m m n m n mn n m mn n m n mn m m n m n m n m m n n n m m n m n m n m n m n m n m n m n m n m n n m n m n m n n m m n mn n mn m m m n m n m n mn n m n n m m n m m n m n n m m mn m n mn n mn n mn mn mn m n m n m n n mn mm mn m n m n mn n m m n m n mn n m mn n m n mn m Yearly areal precipitation generated from observed meteorological station data. m n m n m m n n n m m n m n m n m n m n m n m n m n m n m n n m n m n m n n m m n mn n mn m m m n m n m n mn n m n n m m n m m n m n n m m mn mn n m n mn n mn mn m n mn m n m n n mn mm m n mn m n mn n m m n m n mn n m mn n m mn m n Value (mm) High : 2404 Low : 363 CLIMATE AND RESERVOIR SCENARIOS The years of recurrent drought provoked structural food shortages and hunger. Source: Phillipe Cecchi, SRP Tool Kit. AGRICULTURAL AND HYDROPOWER DEVELOPMENT minimum operational water level •Awareness of the importance of the reservoir water level since the mid 80`s. AGRICULTURAL AND HYDROPOWER DEVELOPMENT VRA Supply / Demand Balance Forecast VRA Transmission Network AGRICULTURAL AND HYDROPOWER DEVELOPMENT Small & Medium Reservoirs: Irrigation Large Reservoirs: Livestock Fishery Household VOLTA BASIN WATER ALLOCATION SYSTEM Volta Basin Water Allocation System (VB‐WAS) Global climate model (GCM) Estimated water demand climate‐hydrological model MM5‐WASIM water supply Historical demand water demand Historical time series small 1991‐2000: and large reservoirs 1991‐2000 Library of water use and demand scenarios Global climate Selection of time series: change surface (IS92a) scenario water withdrawal dry normal 2030‐2039 wet (Volta Basin DATA BASE) specific discharge water use River Basin Management Model MIKE BASIN water availability multisectoral demand ecosystem studies infrastructure planning Selection of time series or water use scenario Selection of climate and policy scenario VOLTA BASIN WATER ALLOCATION SYSTEM •Delineation of hydro-economic catchments for VB-WAS according to national borders and large reservoir catchments. NIGER NIGER MALI MALI R B U R K I N A F A S K O I N B A U R K I F A A F N S A S O O BENIN IVORY COAST TOGO G H A N A MM5/WASIM catchments BENIN IVORY COAST TOGO G H A N A VB-WAS catchments 3000 Hydropower 2000 1000 0 215 ²³ ²³ 220 225 230 235 240 ²³ ²³ ²³ ²³ ²³ Water user per catchment ²³ ²³ # * ²³ ²³ ²³ ²³ ²³ ²³ ²³ !d ²³ ²³ ²³ ²³ ²³ ²³ ²³ •small reservoir abstraction Water demand [m^3/s] Deficit carry-over fraction [()] Groundwater use fraction [()] Groundwater use absolute [m^3/s] ²³ 60 ²³ ²³ ²³ !d ²³ ²³ ²³ # * ²³ # * 40 ²³ 20 0 ²³ 1991 ²³ ´ 50 1993 1994 1995 1996 1997 1998 ²³ 100 Kilometers 200 1999 2000 •surface water withdrawal population density access to safe water source !d # * 0 1992 ²³ ²³ # * VOLTA BASIN WATER ALLOCATION SYSTEM Area [km^2] Volume [10^6m^3] Reservoir !d •large reservoir abstraction large scale irrigation plant discharge simulated_water_level_lake_Volta [m] Simulated water level lake Volta (m) VRA_observed__water_level_lake_Volta (m) [-] VRA observed water level (m) ESA_observed_water_level_lake_volta Satellite observed water level (m) (m) [-] 80 75 1992 TSID 81257 - R41|Water level [m] VOLTA BASIN WATER ALLOCATION SYSTEM VB-WAS Validation period 1992-2000: simulated vs. observed water level lake Volta 1993 1994 1995 1996 1997 1998 1999 2000 TSID 1071 - VRA_observed__water_level_lake_Volta (m) vs TSID 81257 - R41|Water level; Y = 0.798809 X + 16.2075 (R2 = 0.854); LOWESS fit (R2 = 0.858) 82.0 80.0 78.0 76.0 74.0 73 74 75 76 77 78 VRA_observed__water_level_lake_Volta (m) [-] 79 80 81 82 CLIMATE AND RESERVOIR SCENARIOS 1992 m n m n n m n m m n n m n mm n n m m n m n m n n m m n m n m n n m m mn n m n n m m n n m m n mn n m n mm n mn n m mn n mn m n m m m n n m mn n m n m n n n m m n m n m n m m n m n m n mn n m n m mn n m n m n m n n mm n n m m n n m m mn n m n m n m n m m m n m n n m n m n m n m n m n m n m n m n m n m n m n m n n m m n m n m n m n m n m m n n n n m m n m m n m n m n m n m n m n m n m n n m n m n m n n m m n mm n mn m m n n m mn n m n m n m n m n n m m n m n n m m mn m n mn n mn n mn mn mn m n m n m n n mn mm mn m n mn n mn m m n m n n mn m mn n m n mn m A following dry year with an equal magnitude and coverage would have been devastating. dry below average average above average wet 1992 2000 MM5-WASIM simulation 1992-2000 1992 2000 Dry year scenario 1992-2000 2030 2039 MM5-WASIM simulation 2030-2039 CLIMATE AND RESERVOIR SCENARIOS Small and medium Reservoirs Baseline Simulation: Distributed small & medium reservoir development 1991-2000. Historical Scenario: No small & medium reservoir development . Large Reservoirs: the Bui case Bui 2 case: 183 m.a.s.l. full supply 73 m rated head 432 km² flooded area Plant Capacity: 200 m³/s plant discharge 500 m³/s plant discharge Bui reservoir after construction (plus Inundation period) Operational Bui reservoir (no Inundation period) SMALL & MEDIUM RESERVOIR DEVELOPMENT Small and medium reservoir scenario with MM5-WASIM simulation 1992-2000: Baseline simulation vs. historical scenario (no reservoir development) Stored volume lake Volta 1992-2000 baseline simulation [10^6m^3] Stored volume lake Volta 1992-2000 no small reservoirs in Ghana [10^6m^3] Stored volume lake Volta 1992-2000 no small reservoirs in the Volta basin [10^6m^3] 140000 120000 100000 80000 1992 1993 1994 1995 1996 1997 1998 1999 2000 No reservoirs simulation vs. no reservoirs + dry years scenario Stored volume lake Volta 1992-2000 no small reservoirs [10^6m^3] Stored volume lake Volta 1992-2000 no small reservoirs + dry years scenario [10^6m^3] 140000 120000 100000 80000 1992 1993 1994 1995 1996 1997 1998 1999 2000 SMALL & MEDIUM RESERVOIR DEVELOPMENT •The impact of the small and medium reservoir development amounts to a loss of storage of lake Volta of about 6 km³ for the time period 1992-2000. •For the period 1992-2000 the simulated yearly inflow to lake Volta was highly variable (11 – 59 km³). •Climate variabilty, like e.g. a sequence of two dry years causes severe storage losses of lake Volta. •The impact of small and medium reservoirs on the water resources of the Volta basin is marginal compared to their benefit of securing food production during the dry period. LARGE RESERVOIR DEVELOPMENT: THE BUI CASE Impact of operational Bui reservoir on lake Volta storage with inundation period (MM5-WASIM simulation1994-2000). Stored volume lake Volta 1994-2000 [10^6m^3] Stored volume lake Volta 1994-2000 with Bui 200 m³/s plant discharge [10^6m^3] Stored volume lake Volta 1994-2000 with Bui 500 m³/s plant discharge [10^6m^3] 140000 120000 100000 80000 1994 1995 1996 1997 1998 1999 2000 Impact of operational Bui reservoir on lake Volta storage without inundation period (MM5-WASIM simulation 2034-2039). Stored volume lake Volta 2034-239 [10^6m^3] Stored volume lake Volta 2034-239 with Bui reservoir 200 m³/s plant discharge [10^6m^3] Stored volume lake Volta 2034-2039 with Bui reservoir 500 m³/s plant discharge [10^6m^3] 140000 120000 100000 80000 2034 2035 2036 2037 2038 2039 LARGE RESERVOIR DEVELOPMENT: THE BUI CASE •The mean annual evaporation of the Bui reservoir amounts to 55 Mm³ (0.05 km³) for the period 1996-2000 with a projected plant discharge of 500 m³/s. •The Volta basin Water Allocation System (VB-WAS) is a suitable tool to predict the impact of climate variability on the reservoir performance and supports decisions on reservoir management. •A jointly sustainable management of the Akosombo and Bui hydroplants is required to reduce the short term impact of climate variability on the reservoirs performance. REAL TIME OPERATIONAL WATER MANAGEMENT Real time measurements are needed for operational water management: •A data driven modelling framework generating streamflow data from climate data with nonlinear-linear modelling: HYBRID METRIC-CONCEPTUAL (HMC) CATCHMENT MODEL •Network of five hydrological gauging stations that are equipped with satellite transmission systems (Argos) in cooperation with the Hydrological Service Department Ghana (HSD): HYDRO ARGOS HYDROLOGICAL MONITORING SYSTEM CONCLUSIONS Volta basin Water Allocation System (VB-WAS) • Introduce real time discharge data for operational watershed management. • Powerful tool for watershed management considering the impact of climate variability. •Coupled to a dynamic hydrological-economic model (M³ Water) for water policy scenario analysis. •Accounts for national water management strategies and can be used as a supportive tool for transboundary water management. Eva Youkhana Sven Wagner Irit Eguavoen Sonabel Burkina Faso Jan Friesen Nick van de Giesen Ghana Meteorological Agency Hydrological Service Ghana (HSD) Volta River Authority (VRA) Gerald Forkuor Bruno Barbier Julia Eyring Philippe Cecchi Boubacar Barry Wolfram Laube Antonio Rogmann Almut Brunner Charles Rodgers Thank you very much for your attention!!! Je vous remercie de votre attention!!!