Quantifying the potential impacts of land-use and climate change on hydropower reliability of Muzizi hydropower plant, Uganda

Ugandan rivers are being tapped as a resource for the generation of hydropower in addition to other uses. Studies on the reliability of these hydropower plants due to climate and land-use/land cover changes on the hydrology of these rivers are scanty. Therefore, this study aimed to model the impact of the changing climate and land use/cover on hydropower reliability to aid proper planning and management. The hydropower reliability of River Muzizi catchment was determined from its past (1998-2010) and midcentury (2042-2070) discharge at 75 and 90% exceedance probability under Representative Concentration Pathways (RCPs) of 4.5 and 8.5, respectively. The past and projected hydropower were compared to determine how future climate and land-use changes will impact the discharge and hydropower reliability of River Muzizi catchment. Six LULC scenarios (deforestation, 31-20%; grassland, 19-3%; cropland, 50-77%; water bodies, 0.02-0.01%; settlement, 0.23-0.37%, and Barren land 0.055-0.046% between 2014 and 2060) and three downscaled Regional Climate Model (REMO and RCA4 for precipitation and RACMO22T for temperature from pool of four CORDEX (Coordinated Regional Climate Downscaling Experiment) Africa RCMs) were examined. A calibrated SWAT simulation model was applied for the midcentury (2041-2060) period, and a potential change in hydropower energy in reference to mean daily flow (designflow >= 30% exceedance probability), firm flow (flow >= 95% exceedance probability), and mean annual flow was evaluated under the condition of altered runoff under RCP4.5 and RCP8.5 climate change scenarios for an average of REMO and RCA4 RCM. The future land use (2048) was projected using the MOLUSCE (Module for Land Use Change Evaluation) plugin in QGIS using CA-ANN. Three scenarios have been described in this study, including LULC change, climate change, and combined (climate and LULC change). The results suggest that there will be a significant increase in hydropower generation capacity (from 386.27 and 488.1 GWh to 867.82 and 862.53 GWh under RCP4.5 and RCP8.5, respectively, for the combined future effect of climate and land-use/cover changes. Energy utilities need to put in place mechanisms to effectively manage, operate, and maintain the hydropower plant amidst climate and land-use change impacts, to ensure reliability at all times.