An Assessment of the Impacts of Climate Change on Hydropower Potential in West Africa Case study :Bamboi catchment (Black Volta)

Abstract

Due to its low adaptive capacity, West Africa is one of the regions which will be severely affected by climate change. This study is carried out in the main framework of the CIREG project, which is centered towards developing renewable energy generation under changing climate in West Africa. The study evaluated the impacts of future climate change on the hydropower potential of the Bamboi catchment (Black Volta) in West Africa using a conceptual rainfall-runoff model (HBV light model). The hydrological model was successfully validated for the catchment with coefficients (Nash-Sutcliffe efficiencies, KGE, R2) ranging from 0.59, 0.73 and 0.57 respectively during the model calibration and validation phases. Two climate simulations MPI-ESM-REMO of CORDEX-Africa project and GFDL-ESM2M-WRF of WASCAL both under RCP4.5 were applied to the validated hydrological model to simulate the catchment runoff. A statistical bias correction (quantile mapping) was applied to correct the biases inherent in the climate data and two future periods (2020-2049 and 2070-2099) were compared to a reference period (1983-2005). The climate change signals between different periods were compared and impact on the hydrology of the catchment analyzed. Both historical and projected discharges data were converted to hydropower potential following a run-of-river hydroelectricity generation approach. The model mean ensemble projected a temperature increase of 0.8 and 2.8 oC by 2020-2049 and 2070-2099, respectively. Precipitation increase of 11% and 6.6 % for the 2020-2049 period and 10.9 % and 3.7 % for 2070 -2099 are projected by WASCAL and CORDEX climate dataset respectively. Discharge will follow the pattern of precipitation. It is projected to increase by 11 .4 % for 2020 - 2049 period and increase to 9.2% for the 2070-2099 period for climate models mean. On the contrary an overall decrease of hydropower production by -8.9 % and -7.5 (mean ensemble) was projected for 2020 -2049 for corrected and un corrected data respectively compared to reference period. Although, there is a slight increase of hydropower generation near end of the century 2070-2099, compared to the 2020 – 2049 period it is still lower than the historical period -7.7% and -1% for corrected and un corrected data respectively compared to the historical period. These results are explained by an increase in discharge in the rainy season not convertible into hydropower combined with a decrease in discharge during the dry months that leads to important hydropower losses.