Potential Impacts of Future Variation in Temperature and Rainfall on Hydrology and Sediment Yield in a Water Catchment in Central Uganda

Abstract

Upper Ssezibwa catchment is experiencing variations in temperature and rainfall affecting the hydrological process through variable surface runoff, increased sediment yield, siltation of river channels leading to increased flooding in the lower part of the catchment. All of these degrade the environment and affect the sustainability of the water resources. Climate projections indicate a progressive increase in rainfall and temperatures in the catchment and requires attention. Hence, the objective of this paper was to evaluate the potential impacts of future variation in temperature and rainfall on hydrology and sediment yield in a water catchment in central Uganda using appropriate standard methods. Results for Soil and Water Assessment Tool (SWAT) model calibration- (R²=0.85, NSE=0.82, KGE=0.76, PBIAS = -18.5) and validation (R²=0.72, NSE=0.66, KGE=0.66, PBIAS= -19.3) indicate a good agreement with the observed values. The model projected 1.3⁰C and 1.5⁰C increase in temperature and 10.9% and 10.4% relative change in precipitation for the period 2025-2055 under RCP 4.5 and RCP 8.5 emission scenarios. Future projections show climate variability will lead to increase in surface runoff and sediment yield during rainfall peaks is likely to increase river discharge, silting of the river channel and flood occurrence. Quantifying water balance and sediment yield within the catchment is crucial for planning downstream projects and water management generally.