Climate Change Impact on the Hydrology of Tekeze Basin, Ethiopia: Projection of Rainfall-Runoff for Future Water Resources Planning

Climate change impact on Tekeze basin hydrology was studied using bias-corrected ensembles of CORDEX-Africa RCP4.5 and RCP8.5 climate scenarios projections of precipitation and temperature. Soil and Water Assessment Tool (SWAT) used to simulate streamflow and distribution mapping bias correction improves precipitation and streamflow simulations. Tekeze basin showed an increase in mean temperature up to 1.07 degrees C for RCP4.5 and 2.21 degrees C for RCP8.5 climate scenarios in all time periods. Annual, long rain (Kiremt), and dry (Bega) seasons precipitation also showed an increasing trend up to 48%, whereas short rain (Belg) season showed a decreasing trend up to 52% under both RCP scenarios for all future time periods. For this study, SWAT performs well with values of Nash-Sutcliffe efficiency (E-NS) and R-2 greater than 0.7 for simulating streamflow with a reasonable accuracy. Future streamflow in the basin increases and its magnitude varies for each RCP scenarios and projected periods up to 58-66% in dry and 21-55% in rainy seasons. Results from this study indicated that climate changes will affect the basin hydrology and water resources. Due to this future change of streamflow, an input to reservoir operation, climate change scenarios should be incorporated into water resources planning and management of Tekeze basin.