Peter Ashton of the Council for Scientific and Industrial Research has been studying South Africa's water for over 40 years. "The water in many of the country's dams is becoming more enriched with ... sewage, industrial waste, mining waste, agricultural return flows, garbage, and seepage from waste dumps, which is slowly, gradually, building up over time," he said. "That makes it more and more difficult for water treatment companies to take raw water, treat it, and supply it to for people to drink or industries to use. While the volume of water per person is coming down, the quality of that water per person is becoming [worse]."
Currently, South Africa is one of the most heavily dammed countries in the world, and the city of Johannesburg estimates that the city may be the only one in the world not created because its close proximity to a natural waterway. Its water scarcity makes it extremely reliant on dams and increasingly upon the Lesotho Highlands Water Project. By 1998, all of the country's water resources were being used at full capacity.
Ashton considers acid-mine drainage (AMD) to be "one of the greatest threats to South Africa's water" in part because the country's waterways are already heavily burdened. "[Although] it's always been a threat, we've been fortunate in the past that there's been a relatively high buffering capacity in the water. Once that's exhausted [through other contamination], you start to see the acid more visible and travelling further."
Many of South Africa's major water bodies have been or will be impacted by AMD. Of main concern is the Vaal barrage system, which is responsible for supplying a significant amount of South Africa's water: 10-million people draw from the Vaal Dam every day. Already affected by mine waste and other industrial and human pollutants, the barrage is further threatened by Aurora Empowerment System's partial treatment of the Eastern Basin AMD. The cash-strapped mine is the so-called "last man standing" in the basin, pumping water contaminated by operations that have now closed.
Despite being issued a government directive requiring it to pump and treat water, Aurora only partially treats 30-50 megalitres of the 108mL required each day, with the rest being released directly into the barrage.
Increasing coal-mining activity in Mpumalanga poses another threat to the Vaal. "[New mines] are right at the top end [of the river]," explains Ashton. "You'll end up with a lake that is just solid sulfuric acid, which will contaminate the ground water, and the ground water is what feeds our rivers during the dry season." A shift in mining practices could ensure that the Vaal isn't heavily affected, but Ashton is skeptical. "The tendency that I've seen is that business is usual in mining," he says.
Little is known about the potential effects stemming from the mixing of AMD and already contaminated water. According to Jo Barnes, an epidemiologist at the University of Stellenbosch, "there is total ignorance about what is going to happen when [mine] water hits the other problem we have, which is sewage-laden water. What the toxic compounds in the mine drainage will do to the sewage and what resultant health effects in the short term and long term will come from this unholy mix, nobody knows," she says