Assessment of Future Climate Change Impacts on Water Resources of the Upper Kabul River Basin, Afghanistan Using SWAT

Abstract

In this study, climate change impacts on future stream-flow dynamics and water availability are analyzed in the mid-century (2030-2049) and the end-century (2080-2099) using the output of regional climate models (RCMs) under two representation concentration pathways (RCPs 4.5 and 8.5) in the Upper Kabul River Basin (UKRB). A hydrological model was developed using the Soil and Water Assessment Tool (SWAT) from 2009-2019, calibrated from 2010-2016 and validated from 2017-2018. Results indicated, SWAT was capable of simulating the monthly stream-flow dynamics with "satisfactory" to "very good" accuracy. Temperature and precipitation data of four RCMs were bias-corrected using delta change method and were used in SWAT after validation. The future temperature increased in all seasons, the peak occurs earlier in June instead of July in both periods. Future precipitation decreases in spring, while increases in summer, autumn and winter. The precipitation changes are greatest in winter, with a shift of the annual peak from March to February. Changing precipitation in winter combined with increasing in temperature caused an earlier onset of snowmelt with a shift of the discharge peak from June to April/May. The basin’s future water balance is characterized by increasing surface runoff, evapotranspiration (ET), potential evapotranspiration (PET) and total water yield in 2040s and 2090s for both RCPs 4.5 and 8.5. In contrast snowfall and snowmelt are expected to decrease. The future runoff is projected to increase in spring, and decrease in summer (May- August). Thus, a decrease in dry season runoff and increase in wet season runoff is expected.