The coupled impacts of land management and climate variability on the hydrology of the Crocodile River Catchment in South Africa

IntroductionThe Crocodile River Catchment is one of the key water sources for Mpumalanga Province, crucial for irrigation, domestic use, and ecotourism. However, in recent years, the river has reached its utilisation capacity, earning a water-stressed status. Given its socio-economic significance and the potential for urban expansion, water demand is expected to rise, exerting greater pressure on already limited resources. Therefore, in line with integrated water resources management strategies, this study aimed to assess the hydrological effects of land-use management and climate variability on catchment response.MethodologyClimate variability was analysed using the Standardized Precipitation Index (SPI) and the Standardized Streamflow Index (SSI) as a hydrological response indicator, while the SWAT model assessed the long-term effects of land-use/land-cover (LULC) changes on hydrological response.ResultsSince 1980, cultivated lands and commercial forest plantations have grown by 2.5% and 3.1%, respectively, while built-up areas have increased by 2.8%. Model performance was reliable, with Nash–Sutcliffe Efficiency values between 0.2 and 0.73 and the best results at station X2H032 (with R2 of 0.7 during calibration and 0.8 during validation).DiscussionResults indicated that the spatial distribution of evaporation and surface runoff varied significantly with LULC, while climate variability notably reduced surface runoff volumes during dry seasons. The overall streamflow discharge analysis showed a declining trend from 1980 to 2020 at the catchment outlet, consistent with the SPI and SSI findings and the SWAT evaporation and surface runoff results. Consequently, the study highlights that both LULC and climate variability substantially influence the observed hydrological changes in the river.