Streamflow response under different climate change scenarios in data-scarce White Volta basin of West-Africa using a semi-distributed hydrologic model

In this study, streamflow response in White Volta basin of West Africa was evaluated using ECHAM5 (MPEH5) GCM for two IPCC climate change scenarios (A1B and B1) and semi-distributed hydrologic model (SWAT) for three future time periods; 2020s, 2050s and 2080s using 1987-1996 as baseline. Both climate change scenarios project decrease in rainfall in 2020s but increases in 2050s and 2080s. Decrease in rainfall in 2020s was higher in B1 scenario compared to A1B; whereas for 2050s and 2080s, increases in rainfall were higher in A1B scenario than B1. Projected average changes indicate that overall the climate will be warmer and wetter in future. Projected annual streamflow volumes show disproportionate change (similar to 220%) in response to slight changes in mean annual rainfall. Streamflow volume shows sharp changes for A1B scenario than B1 in 2020s whilst in 2050s and 2080s, the changes are moderate. Projected average annual streamflow changes are -3.1% in 2020s, 5.1% in 2050s and 13.3% in 2080s. Overall projected streamflow changes for both A1B and B1 scenarios were not so dramatic (less than +/- 20%). These call for adaptation strategies to reduce vulnerability and ensure water security within the basin.