ASSESSING THE IMPACT OF CLIMATE CHANGE ON GROUNDWATER RECHARGE IN BORKENA RIVER CATCHMENT, AMHARA REGION, ETHIOPIA

Abstract

Climate change has the most severe consequences on water resources, particularly hydrologically sensitive areas such as the Borkena catchment in central Ethiopia. Increased temperature and shifted precipitation regimes have enormous projected impacts on groundwater recharge, surface runoff, and evapotranspiration, the most vital parameters of the hydrologic cycle. Climate change impacts on groundwater recharge over past (1993–2022) and future timescales are analyzed in this study based on the WetSpass model. The trend of observed and projected climate was calculated using the Mann-Kendall test and Sen's slope estimator, while future trends under RCP4.5 and RCP8.5 were derived from the MIROC5 model and bias-corrected via the linear scaling method. In historical trends, temperature increased and rainfall decreased. In RCP4.5, future precipitation is 9.92% and 13.5%, and temperature is 2.58°C and 3.22°C in the mid- and long-term, respectively. With increased rainfall, recharge will decrease by 8.7% and 6.8%, possibly because of increased evapotranspiration and temperature. Runoff and AET are projected to increase by 10.2% and 19.7% in the mid-term, and by 12% and 22.5% in the long-term under RCP4.5. For RCP8.5, rainfall will rise by 21% and 37.8% and temperature rise by 3.6°C and 6°C. Recharge will go down by 5.33% during the mid-period but grow highly by 39.7% during the long-period. Runoff will go up by 14.8% and 31.4% in midterm and long-term respectively, and AET go down highly by 47% during the mid-period and then grow by 50.5% during the long-period. In conclusion, the study points out the extreme vulnerability of other water balance components and groundwater recharge in the Borkena catchment to climate change and demands immediate proactive and adaptive water resource management measures to reduce these impacts