Blood-red spruit causes a stir

Graham, who has been a resident of Paulshof since 1980, was following his well-trodden route home from work across the Braamfontein Spruit when he noticed that the familiar river had undergone an alarming transformation.

“I could not believe my eyes, as the entire river as far as I could see upstream and downstream… had changed its colour to a darkish brick red!” said Graham.

To his further surprise, when he returned the next morning, nothing more alarming than clear water and green algae met his gaze. There was no trace of the strange red stain, and the spruit appeared once more as it always had over the many years spent exploring its shores with his children.

A concerned Graham speculated that the river’s uncharacteristic hue could be due to pollution upstream, but environmental expert Paul Fairall explained that this phenomenon is completely natural.

“We receive numerous calls saying people are throwing oil into the river, or there is acid mine drainage. It’s not the case,” said Fairall.

“Sixty percent of water precipitation moves laterally through the soil profile,” he explained.

According to Fairall, the water seeps into waterways, bringing metals and minerals from the soil strata. The red hue that Graham noticed is caused by a reduction of iron, which can be accompanied by a reduction of manganese causing a silvery sheen on the water’s surface.

He said the process is more evident during winter, when dry weather means less runoff into the rivers and more of the water is underground. The Halfway House Granite Dome is responsible for the regular instance of this geological phenomenon in the north of Johannesburg.

Graham and other Paulshof residents have no reason to worry about their beloved spruit – but the potential for humorous comment remains. After describing the experience as Biblical, Graham said, “One colleague remarked that ‘I should really get worried if the river parted for me to walk across’!”