Scores of fish have perished in a highly polluted stretch of the Vaal River this week in what has been described as a “serious fish kill”.
High levels of sewage pollution from Emfuleni local municipality’s malfunctioning wastewater management system have caused fish to suffocate in the Rietspruit, an “open sewer”, said local environmental NGO Save the Vaal Environment (Save).
“The stance of the Department of Water and Sanitation (DWS) is that this is a weather phenomenon,” said Maureen Stewart, of Save.
“We see it differently. The increasing amount of sewage in the Vaal River, especially from the heavily polluted Rietspruit tributary, is depleting oxygen in the water. This is the main reason for the fish deaths.”
Sewage that is spewed into the Rietspruit, flows into Loch Vaal, which in turn flows into the main Vaal River, through the Vaal Barrage downstream to Parys.
Rand Water’s Barrage latest weekly water quality analysis for the Loch Vaal shows E coli counts, indicative of sewage in the water, totalling 2.9million counts of E coli per 100ml of water - 400 counts per 100ml is considered dangerous to human health.
“The fish deaths are aggravated by the weather and the heat we’ve had. But the cause is the oxygen depletion in the water from the high levels of nutrients in the water because of the incredibly high E coli counts in the mouth of the Rietspruit. This is where all the fish deaths are taking place.
“It’s a disaster. Fish are lying all over the riverbanks and there are dead fish in the river. We’ve told the council that they have damaged the ecosystem to such an extent that this fish saga has now happened again,” Stewart said.
The blame, she believes, is to be laid firmly at the door of the DWS and the municipality “because no action has been taken on the ground to resolve this issue”.
Emfuleni did not respond to the Saturday Star but DWS spokesperson Sputnik Ratau, said: “Seemingly what it is, is two things: it’s the heatwave, which causes evaporation and sucks out the oxygen; compounded by the wastewater pollution. That combination is one that basically sucks out all the oxygen in the water.”
Last July, the DWS was criticised after it blamed a mass fish die-off in the Vaal on seasonal weather changes.
Water expert Professor Anthony Turton said, he too, had been alerted to the fish deaths in recent days.
“There’s now empirical evidence of fish kills, fish are lying dead everywhere What happens as a result of temperature and other environmental factors is that sometimes the water becomes anoxic - there is insufficient oxygen to sustain fish life so you get these massive fish kills.
“The question is what makes the water anoxic? We know high nutrient loads create a rapid proliferation of single-celled creatures, some of which are algae cells. They absorb the oxygen and make the water anoxic.
“We can establish high levels of nutrients from the sewage is coming in from inter alia, the sewage flows, resulting in anoxic conditions, which result in fish kills. The cause and effect linkage in that whole chain of evidence is clear.”