The river that feeds Gauteng: Toxic sediments found in the Klip | News24

• New University of Johannesburg research found toxic chemicals in the Klip River exceeding international safety benchmarks.
• The river feeds into the Integrated Vaal River System, a key water supply network for Gauteng.
• High levels of polycyclic aromatic hydrocarbons pose risks to aquatic life and long-term human health.

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Johannesburg’s Klip River feeds directly into Gauteng’s main water system – yet new research released in March by the University of Johannesburg shows toxic chemicals are accumulating in its sediments at levels exceeding international safety benchmarks and known to pose risks to aquatic life and long-term human health.

Flowing roughly 100km from Johannesburg’s southern watershed to the Vaal Barrage, the Klip River feeds into the Integrated Vaal River System, one of South Africa’s most strategic water supply networks.

In several urban stretches, however, the river foams after spill events, carries sewage odours and runs discoloured past dense residential neighbourhoods.

Researchers from the University of Johannesburg’s Process, Energy and Environmental Technology Station detected elevated concentrations of polycyclic aromatic hydrocarbons (PAHs) in Klip River sediments.

These toxic chemicals were recorded at levels of up to 7.41mg/kg in some samples. International sediment quality guidelines generally consider total PAH concentrations above 4mg/kg as a level where harmful biological effects become increasingly likely – meaning some Klip River samples exceeded commonly accepted risk benchmarks.

When zebrafish embryos were exposed to the sediments under laboratory conditions, many developed deformities, hatched late or died. Mortality rates reached as high as 80%.

READ | Dangerous chemicals found in Gauteng’s Klip River

The broader KlipWaS study describes the river as “one of the most complex and environmentally significant freshwater systems in the Upper Vaal catchment” – but one operating under “cumulative pollution and ecological stress”.

Researchers examined nine monitoring sites across the catchment using chemical testing, microbial analysis and spatial mapping. Their findings show contamination is not confined to a single spill or facility.

“Pollution patterns are structured by tributary inflows, infrastructure networks and land use rather than by a uniform downstream decline,” the report stated.

In practical terms, pollution introduced in one part of the system does not simply dilute and disappear. It can accumulate in wetlands and sediments and persist long after discharge events.

Andrew Barker, the chairperson of the Klipriviersberg Sustainability Association (KlipSA), said repeated wastewater failures have become embedded in the catchment.

“The Klip River is not just suffering from occasional spills.”

He added:

“That changes the ecological baseline. The system is no longer responding to isolated incidents – it is absorbing sustained pressure.”

Natural buffers under pressure

Historically, the Klip River was supported by extensive wetlands that slowed floodwaters, trapped sediments and immobilised contaminants. The KlipWaS report described these areas as providing a “protective function of intact vegetation and natural drainage pathways”.

However, the study noted that wetland degradation and urban expansion have reduced this buffering capacity, “increasing the vulnerability of the system to cumulative pollution”.

Some tributaries flowing through less-developed areas still showed relatively healthy water quality – evidence, researchers said, that parts of the system remained capable of recovery.

The report stated:

Official response

Justice Mohale, the spokesperson for Rand Water, said the bulk supplier conducted biannual monitoring for persistent organic pollutants across strategic sites in the Vaal Dam and Vaal River Barrage catchments, including monitoring points associated with the Klip River system.

“The relatively polluted Klip River enters the Vaal River system downstream of Rand Water’s abstraction points,” Mohale added. “It therefore has no impact on Rand Water’s raw and subsequently treated water quality.”

He said investigations into hydrophobic micropollutants, including PAHs, found none detected at levels of concern in raw or potable water, and that risks to Gauteng’s treated supply are “well mitigated”.

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The Department of Water and Sanitation stated that contamination from tributaries, such as the Klip River, was incorporated into the Vaal River risk modelling. However, sediment sampling is not currently part of routine monitoring, and PAHs are not included as standard testing parameters.

The department indicated that incorporating sediment sampling would provide a clearer picture of long-term contamination trends.

Communities stepping in

Across the Klip River catchment, at least 13 identified intervention sites – including wetland rehabilitation projects, constructed treatment wetlands, stewardship zones and water-quality monitoring points – are active, coordinated and supported by KlipSA and community partners.

In Orlando West, the Klipspruit–Emaplatini community stewardship initiative focuses on restoring a vulnerable tributary wetland feeding into the Klip River.

“I started cleaning the river as a child,” said community organiser Franse Ngcobo. “Later, when I was studying, I continued. Thousands of tourists pass through here each month, but many don’t realise this river is part of our history.”

The project combines solid-waste removal, sewage inflow reporting, tree planting, door-to-door environmental education campaigns and recycling awareness programmes in local schools.

Further south in Adamsholf, a KhoiSan custodianship initiative blends ecological restoration with cultural practice.

“Our role is custodians,” said Chief Johannes Ralph Goliath. “Water is a living entity, not a dumping ground.”

Across the Klip River catchment, at least 13 identified intervention areas are active, ranging from wetland rehabilitation to citizen science monitoring. These are coordinated and supported by KlipSA and community partners.

This story is produced by Our City News, a non-profit newsroom serving the people of Johannesburg.