Abstract:
Land-use changes and climate variability are known to affect environmental processes, and fluvio-marine environments tend to be extremely sensitive to these impacts. Hydrological models have been introduced in numerous studies to explore the responses in catchment processes. Spatially distributed rainfall-runoff models provide a more holistic view of the hydrological behaviour under different environmental conditions. However, the use of hydrological models in South African studies which investigate the impacts of climate and land-use change on discharge are scarce, and only a limited number have investigated the impact of climate and land use on catchment processes. What is of more relevance and importance in real-world applications is the differentiation between the respective roles of climate and land use on specific catchments. This study implements Spatial Tools for River basin Environmental Analysis and Management (STREAM), a GIS-based water-balance model, to investigate the major causes in change of discharge volume in the Amatikulu and Nyoni catchments (KwaZulu-Natal, South Africa). River and coastal morphological changes have also been observed in the recent past. This study proposed that land-use changes and climate variability have the largest influence on the change in discharge volumes; however, the exact extent needs investigation. Climate and land-use data for the period 1964-2015 are used for the model simulations. It has been found that land-use changes have had no significant impact on the discharge for this period, while climate has had the larger effect. Climatic scenarios corresponding to projected climate change have been investigated, and have shown that a 5°C increase in temperature would have the largest influence on discharge compared to the observed changes in land use.
