"I've Learned Something": SA Engineer Breaks Down Hartbeespoort Dam's Hyacinth Crisis in Video

• Engineering Explained SA broke down why Hartbeespoort Dam is covered in thick green water hyacinth in a viral video
• The engineer traced the problem to millions of litres of poorly treated sewage flowing into the dam from Gauteng municipalities daily
• South Africans watching the video said the explanation opened their eyes to a crisis hiding in plain sight

Anyone who has visited Hartbeespoort Dam recently knows something is off. The water is not blue or even murky brown. It is a thick, suffocating green, blanketed by water hyacinth so dense it looks like a lawn floating on the surface.

A page called Engineering Explained SA published a Facebook video on 31 August 2026 breaking down exactly how the dam ended up this way, and why it has been so difficult to fix.

Sewage is feeding the problem

The video explains that Hartbeespoort Dam sits at the bottom of a massive catchment area. Rivers draining large parts of Johannesburg, Ekurhuleni and surrounding areas flow into it, carrying with them millions of litres of inadequately treated sewage from failing municipal wastewater treatment works across Gauteng every single day.

Read also

Philippine couple gets married in hip-deep floodwaters after refusing to postpone wedding

That sewage is rich in the same nutrients found in commercial fertiliser. Water hyacinth, introduced to South Africa in the late 1800s as a decorative garden plant, feeds on exactly those nutrients and thrives under those conditions. The plant can double its mass in under two weeks, which makes it nearly impossible to control once a system is saturated with what amounts to industrial-grade fertiliser.

Every fix has failed so far

Authorities have tried multiple approaches over the years. Weeds killer was restricted because mass die-offs send millions of plants to the bottom, stripping oxygen from the water and suffocating marine life. Mechanical harvesting cannot keep pace with how fast the plant regrows. Biological control using insects bred to damage the hyacinth has had some effect but cannot outpace a system flooded with nutrients.

The most recent experiment involves pumping oxygen back into the water to counter the damage. Each approach buys time. None addresses the root cause.

Read also

Trevor Noah’s old ‘world-class pilots’ joke takes on new meaning after Airlink flyover

The engineer compared the situation to painting over a damp patch on a ceiling. The stain keeps returning not because the paint fails, but because the leaking pipe above was never repaired. The real fix, the video argues, lies hundreds of kilometres upstream, in upgrading the wastewater treatment works discharging into the rivers that feed the dam.

View the Facebook video below:

South Africans react to the eye-opening breakdown

Viewers were quick to share their thoughts on Engineering Explained SA's page:

@Mbasa Xolisa Tshombe wrote:

"Brilliantly explained. This situation is just like the story of the now non-existent Centurion Lake."

@Matthew Bodenstein said:

"Nicely explained! Also providing a possible solution."

@Caro Mannafela added:

"Same like Benoni lake."

@Debbie Du Plessis asked:

"While you wait for the sewerage problem to be solved, is there a possibility of composting the nutrient-loaded plants and selling them?"

@Jack Phosa commented:

"Thank you for the kind of education. I've learned something."

More Briefly News stories on dams

• Durban amputee paddler Tony Botes and a teenage bystander bravely rescued a man from drowning in the uMngeni River during a religious ceremony.
• A safari vehicle plunged into the crocodile-infested Mara River, forcing the driver and tourists to escape as onlookers rushed to help in a terrifying ordeal.
• Amber-Rose Berry, 18, made history as the youngest South African woman to swim the English Channel, completing the roughly 33km crossing from England to France in 10 hours and 27 minutes

Source: Briefly News