A second source of pollution is runoff and wind-eroded particles from slime dams - soil residue from within the mines that often contains radioactive elements and heavy metals. On a recent site visit south of Carletonville, residue from eroding slime dams was observed washing down dirt roads towards drainage canals that empty into the Wonderfonteinspruit.
A 2007 report by the National Nuclear Regulator (NNR) stated: "These slime dams and rock dumps are potentially significant contributors to diffuse contamination."
Wind-blown radioactive dust particles from the slime dams could also pose "significant radiation exposure" through inhalation or by contaminating agricultural crops, while cattle posed a serious problem because they churned up sediment loaded with radioactive elements and heavy metals in the waterways when they went into them.
After the NNR's report was released, the largest mining company operating in the area, Harmony, issued a directive to land and water users in the area, saying that cattle should no longer be watered in the river.
Thus far, the more proactive steps are coming from the local community. The Merafong Council, which includes the town of Carletonville and surrounding district, has put up signs warning people to not use the water and has provided drinking water to informal settlements on the river's banks.
"Although Water Affairs in their latest reports indicate that the water itself is safe, it is a known fact that there are sediments that are contaminated with radiological elements," said Albie Nieuwoudt, Strategic Executive for Economic Development, Planning, and Environmental Management at Merafong.
"That's why we put up the signs. We've just created our own Environmental Management section to look at issues arising from dust and slime dam residue; we've got a duty to protect our citizens."
Frustrations with government
Rene Potgieter, a former peat farmer who now works on the Wonderfonteinspruit contamination issue, said, "We have a group here organised through DWAF where water quality is monitored. I sit on the committee, and on a regular basis we look at what the discharge water qualities are. You just see noncompliance, noncompliance, noncompliance. But all DWAF does is monitor - they don't do anything with those results."