The knowledge of the influences climate change can have on a regional scale is still very limited. Generally it is known that the climate, land use, energy and water resources are intertwined. The CLEW strategy focuses on an approach to quantify these interrelations. In South Africa, experiencing a fast development, water resources are vital for a continuous prosperous growth. Through a methodological approach the local impacts of climate change on water supply and demand for the City of Cape Town are analysed. The focus lies on the Theewaterskloof Dam in the Riviersonderend catchment. For this study, the future climate data are generated in MarkSim for different SRES scenarios. Using the Water Evaluation And Planning system simulation software WEAP the catchment of interest is modelled to estimate future variation in water availability. For all scenarios the findings are consistent with prior studies forecasting an increase in the annual mean temperatures and a decrease in the annual precipitation. The reduction in annual precipitation consequently leads to a decreased water availability in the Riviersonderend catchment. Despite of the fact that the water resources are likely to diminish, the fixed annual water demand supplied by the Theewaterskloof reservoir is expected to be covered in the future without limitations.