Is it sewage or neglect behind the aquatic invasive free-floating Kariba weed choking Lonehill Dam?

That’s the question dividing residents and local officials as the water body continues to deteriorate. Nadeem Abrahams, environmentalist from the Lonehill Residents Association, has previously said the sewage contamination is a key factor behind the dam’s rapid decline, arguing that nutrient-rich runoff is fuelling the explosive growth of the weed.

Ho wever, Ward 94 councillor David Foley has pushed back against the assertion that sewage is the primary cause, saying the situation may be more complex and requires proper scientific testing before conclusions are drawn.

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That is why Foley called for a recent inspection by Johannesburg Water’s Zandfontein sewage team after reports of intermittent sewage traces appearing in stormwater channels along Forest Drive, which eventually feed towards the dam area.

These are the same channels that Abrahams has also suspected of eventually leaking into the dam and reported to Johannesburg Water.

Foley said, “What we saw [with the Zandfontein sewage team] is not a constant flow, but something that seems to happen after heavy rainfall. There is a stormwater channel coming from nearby complexes, and we suspect that during overflow events, something may be entering that system.”

He said during the site visit, officials did not find an active sewage leak, but added there was evidence suggesting recent contamination.

“There were small remnants, like toilet paper, which indicate that sewage had been present at some point.”

He said the investigation will now focus on nearby residential complexes, where teams are expected to inspect sewage manholes and infrastructure to determine whether there are incorrect connections or overflow into stormwater systems.

He added that the Johannesburg Roads Agency is also expected to assist in mapping the drainage network.

Also read: Lonehill Residents Association reassures community on dam efforts

While concerns persist about the dam’s condition, Foley said it is important not to assume contamination without formal testing.

“With the amount of rain we’ve had, the dam is constantly being refreshed. The only way to confirm any level of contamination is through proper water sampling and environmental testing.”

Foley argued that while pollution may contribute, the unchecked growth of Kariba weed is also strongly influenced by the lack of maintenance and seasonal conditions.

“These plants can spread rapidly in warm conditions and will take over if not actively managed. If there hasn’t been regular clean-up, the situation can escalate quickly.”

He added that no major maintenance has been carried out at the dam in recent months, which may have worsened the infestation.

The water utility was contacted for comment on March 26.

“Your query is noted. We will respond within our standard turnaround time of 48 working hours, depending on the complexity of the matter and the input required from relevant technical departments,” said Phakamani Ndlovu from Johannesburg Water.

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