Assessing Hydrological Responses to Climate Change in the Olifants River Basin Under RCP and SSP Scenarios, South Africa

Climate change has a significant impact on global hydrological processes and water resource availability. Compared to global challenges, the Olifants Basin (ORB) also faces pronounced effects of climate change on its water resources. This study aims to investigate the impact of climate change on the hydrological water balance components under RCP and SSP scenarios using the SWAT+ model. The model's sensitive parameters were identified, and its calibration (NSE, R2, and PBIAS = 0.76, 0.78, and 5.76, respectively) and validation (0.77, 0.82, and 12.22, respectively) were conducted and showed satisfactory performance. 6Moreover, under the SSP245, water yield and surface runoff are projected to decline by 44.02%, 44.16%, 51.2%, and 51.35% in mid-term (2030–2060) and long-term (2070–2100), respectively. Similar decreasing water yield and surface runoff patterns were observed in the mid and long term under SSP585, with reductions of 60.8%, 61.75%, 59.03%, and 58.98%, respectively. Declining water yield and runoff patterns were observed in the mid and long term under SSP and RCP scenarios. Specifically, under RCP4.5 and RCP8.5, surface runoff is projected to decrease by 50.89% and 47.52%, respectively, and by 46.94% and 68.28% in the long term. In general, projections under RCP scenarios indicate a decline in water yields across all future periods, with a more pronounced decline under high-emission scenarios, reaching 66.94% in the far future. Therefore, climate adaptation strategies, climate-resilient agricultural practices, integrated watershed management, and enhanced water use efficiency are necessary to safeguard sustainable water resource availability.