Assessment of climate change impacts on hydrological processes in the Usangu catchment of Tanzania under CMIP6 scenarios

Climate change is anticipated to have long-term effects on hydrological processes and patterns, leading to water stress in agroecological catchments. Climate change escalates water scarcity in the Usangu catchment, as evidenced by the drying up of rivers during the dry season. Therefore, this study was undertaken to assess climate change impacts on hydrology by utilizing the Soil Water Assessment Tool (SWAT) model and an ensemble mean of five Global Circulation Models (GCMs) under two shared socio-economic pathway (SSP) emission scenarios. Downscaling of GCMs was performed by the LARS-WG statistical downscaling tool. In comparison to the baseline period, short rain intervals are expected to occur between 2030 and 2060, with a mean annual precipitation increase of 7 and 17% in SSP 2-4.5 and SSP 5-8.5, respectively. Maximum and minimum temperatures are expected to rise by 0.6-2 degrees C. Corresponding to future temperature increases, evapotranspiration would increase to about 30% and decrease water yield and groundwater recharge by 7 and 26% in SSP 2-4.5 than in SSP 5-8.5. However, the effect of precipitation increase is shown by increased surface runoff and streamflow during wetter months. These findings provide watershed managers with crucial information for planning and managing the catchment in light of a changing climate.