Impact Of Climate Change On Water Balance Components In Upper Kabul River Basin,Afghanistan

Afghanistan is a semi-arid country with a mountainous terrain that has been ravaged by conflict for three decades,one of the world’s most vulnerable countries because of a lack of climate mitigation capabilities.Yet,the variability and intensity of the adverse effects of climate change on water resources are not well understood.The present study emphasized the evaluation and interpretation of climate change and its influences on water balance components over the periods of the 2030 s,2050s,2070 s,and the 2090 s in the Kabul River Basin(KRB),which is one of Afghanistan’s five major river basins and has been severely impacted by climate change.Climate change including temperature and precipitation analysis has been studied using four climate models(Can ESM5,MIROC6,MPI-ESM1-2-LR,and NESM3)from the CMIP6 under SSP2-4.5 and SSP5-8.5 scenarios.The Global Climate Model(GCM)data have been selected for the historical period 1929-2014 and the future period 2022-2099.The data was downscaled using the LARS-WG model as a statistical model to improve the reliability of GCMs.The correlation of the generated climate data was typically similar to the measured climate data.The Mann-Kendall trend test was used to analyze climate trends over the past four decades,the results revealed an increase in temperature by 0.89℃ and precipitation by0.26 mm.The annual maximum projected temperature increase ranged from 2.54℃ to 3.50℃ under SSP2-4.5,and 3.0℃ to 5.02℃ under SSP5-8.5.The annual minimum temperature showed an increase of 2.0℃ to 2.8℃ under SSP2-4.5,and 2.9℃ to 4.0℃ under SSP5-8.5.The annual precipitation decreased by 11.7% to 5.6% from the 2030 s to the 2090 s under SSP2-4.5.Under SSP5-8.5,the annual precipitation decreased by 0.1% in the 2030 s and by 0.6% in the2050 s,whereas it increased by 5.4% in the 2070 s and 4.7% in the 2090 s respectively.The assessment of climate change impacts on water balance components was studied using a good calibrated and validated Soil and Water Assessment Tool(SWAT)model with the inputs of the developed GCM scenarios.The findings revealed that annual streamflow decreased by 12.0% under SSP2-4.5 and showed a slight increase of 5.1% under SSP5-8.5.Similarly,runoff decreased by 21% under SSP2-4.5 and showed a slight increase of 1.2% under SSP5-8.5.The annual water yield showed a decrease of 15.6% under SSP2-4.5 and a slight increase of 0.8% under SSP5-8.5.Evapotranspiration(ET)increased under both scenarios,which ranged from 8.4% under SSP2-4.5 to 24.2% under SSP5-8.5.The study revealed a variation in monthly water components,where the most significant increase in monthly streamflow,runoff,and water yield by 52.2%,86.6%,and 70.4% was observed in August under SSP2-4.5,and by 68.3%,105.0%,and 83.5% in September under SSP5-8.5,respectively.Similarly,evapotranspiration significantly increased by 89% in August under SSP2-4.5 and by 91.9% in December under SSP5-8.5.The streamflow and water yield showed the largest decreases of 22.2% and 27.0% in March under SSP2-4.5,and 8.6% and22.8% in May under SSP5-8.5,respectively.The surface runoff and evapotranspiration significantly declined by 36.3% and 15.3% in February under SSP2-4.5,and by 39.6% and22.8% under SSP5-8.5 for the same month.This study gives crucial information about water resource management and planning in the upper KRB in light of climate change.