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Extensive karst aquifers developed in compartmentalized dolomitic strata constitute important groundwater reservoirs in semi-arid parts of South Africa. Located in the vicinity of densely populated and increasingly water-stressed metropolitan areas of Gauteng, these aquifers are of strategic importance for future water supply. However, many of the dolomitic groundwater compartments are severely affected by deep-level gold-mining operations. Apart from large-scale dewatering and associated modification of spatial and temporal water availability, gold mining also adversely impacts on the quality of remaining water resources. The focus of this paper is on uranium, a chemically toxic radioactive heavy metal identified by a number of previous studies as the contaminant of concern. Point- and non-point sources of U associated with mining activities in the Wonderfonteinspruit catchment, as an example of a dolomitic gold-mining area, as well as pathways of U pollution are discussed. Associated U loads emanating from major sources are estimated. The results suggest that detected levels of U pollution in the catchment are not only caused by century-old mining activities but also by current operations and that U pollution of water is likely to continue well beyond the closure of mines.