IMPACT OF CLIMATE CHANGE ON WATER BALANCE COMPONENTS IN THE UPPER AWASH SUB-BASIN OF ETHIOPIA USING SWAT MODEL

Abstract

Climate change poses significant challenges to water resources, agriculture, and ecosystem sustainability in various regions worldwide. The present study investigates the trends in hydro-climatic variables and projects future changes in water balance components for the Upper Awash Basin in Ethiopia. Detections of trends in hydro-climatic variables were performed by using the Modified Mann–Kendall test. Trend analysis for historical (1991 –2020) rainfall and temperature data from multiple stations revealed significant increasing trends in annual and kiremt (summer) season while decreasing trends were observed for belg (spring) and bega (winter) seasons. Streamflow trend analysis at the hombole station indicated a significant negative trend in annual (−84.06 m3/s) and in kiremt (summer) (−77.41 m3/s) seasons, highlighting potential water scarcity concerns. The SWAT model was calibrated and validated against observed streamflow data for the 1999–2015 period. Model performance was reasonable during the calibration (1999-2008) and validation (2009-2015) period, the model performed well with NSE values of 0.76 and 0.76, R² values of 0.75 and 0.76, and PBIAS values of +2.5% and +9.6%, respectively. The ensemble of GCMs revealed that the annual maximum and minimum temperatures, precipitation, water yield and streamflow were predicted to increase up to 2.77°C, 4.40°C, 26.30%, 49%, and 58% respectively, but evapotranspiration decreased by −4%, in the period of 2080s (2066-2095) under the SSP5-8.5 scenario. The findings underscore the pressing need for climate adaptation measures, sustainable land management practices, water conservation initiatives, and resilient agricultural systems to mitigate the impacts of climate change on local ecosystems and livelihoods.