Climate change impact on West African rivers under an ensemble of CORDEX climate projections

In the context of a region-wide hydropower potential study, the impact of climate change on the hydrology of West Africa was assessed. Climate data of 30 Regional Climate Model simulations of the CORDEX initiative based on two emission scenarios (Representative Concentration Pathways RCP4.5 and RCP8.5) were applied in a water balance model. Future changes in the water balance for an area of 3.7 million km2 and resulting changes in river discharge in 500,000 river reaches were investigated for two future periods, 2026–2045 and 2046–2065. This article focuses on 12 key locations in the 10 largest river basins, and all results for the entire West Africa region are publicly available via the ECOWAS Observatory for Renewable Energy and Energy Efficiency (www.ecowrex.org/smallhydro). For large parts of the region, projected changes in climate do not lead to substantial reductions in river discharge, with median results of the model ensemble in the range of ±5%. Stronger decreases in discharge are projected for regions in the north and east of West Africa, pronounced increases mainly for the southwest. The application of a large climate model ensemble exhibits the high uncertainty related with these projections, but also shows regions with high agreement between results with different models. The regional climate change impact analysis provides a baseline for climate-informed decision making for hydropower development and other fields of water management and water policy and enables regional focus for initiating further research and developing adaptation pathways.