Assessing Streamflow Response to Climate Change Under Shared Socioeconomic Pathways (SSPs) in the Olifants River Basin, South Africa

Climate change affects streamflow through changes in precipitation, temperature, and extreme weather events. These changes will impact water resource availability significantly. Thus, understanding the impacts of climate change on hydrology is essential for sustainable water management. This study investigated the potential effects of climate change on streamflow in the Olifants River basin under shared socioeconomic pathways (SSPs), utilizing the restructured version of the Soil and Water Assessment Tool (SWAT+) model. Projected precipitation and temperature (Tmax and Tmin) were analyzed for the near (2030–2060) and far (2070–2100) future to simulate and analyze streamflow variations under SSP245 and SSP585 scenarios using bias-corrected CMIP6 data and the SWAT+ model. The SWAT+ model was calibrated and validated successfully, with Nash–Sutcliffe efficiency (NSE) values of 0.76 and 0.77, and coefficient of determination (R²) values of 0.78 and 0.82 during the calibration and validation periods, respectively. Climate model ensemble projections show a consistent decline in precipitation and increases in Tmax and Tmin, with Tmin increasing more significantly. These changes are projected to reduce streamflow, with annual declines of 43.08% and 50.89% under SSP245 and 57.79% and 58.82% under SSP585 for the near and far future, respectively. Moreover, climate change reduces streamflow across all seasons in the Olifants River basin. Therefore, adopting water management strategies such as enhancing integrated water resource management and investing in climate-resilient infrastructure is essential for sustainable water resource management under changing climate conditions in the basin.