Sustainable Management of Water Resources in a Semi-arid River Basin Under Climate Change: A Case Study in South Africa

Rapid population increase, industrialization, and pollution are putting a strain on available and diminishing freshwater resources. The main aim of this paper is to model the impact of climate change scenarios on the availability of water resources in a semi-arid river basin in South Africa and to provide options for sustainable management and adaptation strategies. In this paper, a dynamically downscaled data was derived from the GCM (general circulation model) simulations of the Coupled Model Inter-comparison Project Phase-5 (CMIP5) and across two greenhouse gas emission scenarios known as Representative Concentration Pathways (RCP) 4.5 and 8.5. The spatial resolution of the dataset is 50 km × 50 km. Eight GCM (climate models) were used for this set of data. A Soil and Water Assessment Tool (SWAT) model was run using these data for a period of up to end of the century (2020–2100) and the results were then compared with long-term historical data. Comparison of measured data with simulated historical data showed a strong correlation (R2 ≥ 0.9), which is indicative of the reliability of projected future climate. Varied results were obtained depending on the type of climate model used, but generally the trends were similar in most cases. However, the multimodel average showed a possible decrease in precipitation (up to −3%), a decrease in water yield (up to −13%) and an increase in potential evapotranspiration (ET) (up to +22%). The latter is indicative of possible drought spells between rainy events. It is expected that the results of this research will assist in policy formulation to mitigate the negative impact of climate change in the region.