Hydrological response to climate change in the Deme watershed, Omo-Gibe Basin, Ethiopia

Abstract Climate change is believed to have led to changes in global patterns. This study evaluated the hydrological responses to climate change in the Deme watershed using the Soil and Water Assessment Tool (SWAT) for two consecutive periods of 2031–2050 and 2051–2070. Climate variables were downscaled from RACMO22T, under RCP4.5 and RCP8.5 scenarios from CORDEX-Africa. Distribution mapping and variance scaling methods were used for bias correction of precipitation and temperatures, respectively, and for further analysis. The SWAT model was calibrated (and validated) for the 1989–2000 (2001–2010) period, and the hydrological model showed a reasonably good agreement. The result shows that the rainfall and streamflow show a decreasing signal in the wet season. The maximum projected change in annual temperature, PET, and ET was 2.15 °C, 10.89, and 9.24%, respectively, in the far future period under the RCP8.5 scenario. These incremental changes have an impact on declining annual rainfall and streamflow up to 27.6 and 26.2%, respectively, under the RCP8.5 scenario in 2031–2050. The subsequent results were the maximum decline of surface runoff by 15.10%, groundwater by 14.78%, and total water yield by 26.10% in 2031–2050 under the RCP8.5 scenario. Thus, the concerned body integrates its duties with climate change.