MINE WATER FOOTPRINT IN THE JOHANNESBURG AREA, SOUTH AFRICA: ANALYSIS BASED ON EXISTING AND MEASURED DATA

Groundwater quality in the Johannesburg area has been severely affected by mine water. Surface and ground water quality characteristics have been thoroughly assessed based on water chemistry. The results show that the dilution factor for mine water in the receiving streams ranges from 41% to 90% as a result of interaction with the dolomitic water that has an alkaline nature. The estimated SO4/C1 ratio lies between 0 and 306, while the Fe/Ca ratio ranges between 0 and 6. High SO4/C1 (>0) and Fe/Ca (>2.5) values potentially indicate the interference of mine water with the groundwater system. The closure of mines in the Johannesburg area has resulted in a long-term rise in the groundwater level, with a rate that varies between 1 m/y and 2 m/y, which can be related to the widespread plume of rising mine water in the aquifers. This severely impacts the quality of fresh water resources.