Modelling the effects of climate change on streamflow using climate and hydrological models: the case of the Kesem sub-basin of the Awash River basin, Ethiopia

Abstract

The sign of climate change and its impact is revealing on different natural and synthetic systems. The objective of this study was to analyze and quantify the impacts of climate change on streamflow in Kesem sub-basin, Middle Awash River basin, Ethiopia. Ensemble mean of four Coordinated Regional Climate Downscaling Experiment (CORDEX) Africa regional climate models operating under two alternative scenarios of Representative Concentration Pathways (RCP 4.5 and RCP 8.5) was used. The period from 1975 to 2005 was used for the analysis of the baseline scenario while the periods 2050s (2020–2049) and 2080s (2050–2080) were used for future scenarios analysis. The impact assessment on streamflow was done using soil and water assessment tool (SWAT) hydrological model. The statistical performance of the SWAT model in simulating the streamflow was shown with coefficient of determination (R²) of 0.84, R-Factor of 0.56 and Nash-Sutcliffe Efficiency (NSE) of 0.78 for monthly calibration and R² of 0.78, R-Factor of 0.67 and ENS of 0.73 for monthly validation periods. Mean monthly changes in precipitation and temperature (maximum and minimum) were used to quantify these impacts. The result of bias-corrected precipitation and temperature disclosed a logical increase in all future periods for both RCP 4.5 and RCP 8.5 scenarios. These changes in climate variables created an increase in mean annual streamflow by 14.5 and 19.1% for RCP 4.5 and by 4.7 and 6.9% for RCP 8.5 scenarios of the 2050s and 2080s, respectively. This result provides valuable information for guiding current and future water resource management in the Kesem sub-basin and similar other areas in Ethiopia.