One of South Africa’s biggest dams is so polluted you cannot see the water

Hartbeespoort Dam is so polluted that a hyacinth mat covers the surface, making it dangerous for boaters and harming the ecosystem.

The Hartbeespoort Dam, also known as Harties, was constructed 100 years ago and was renovated in 1969.

The dam wall is 149.5 metres long and 59.4 metres high, and it can store 195 million cubic metres of water.

It is built across a gorge cutting through the Magaliesberg, and the Crocodile and Magalies Rivers feed the dam.

Hartbeespoort Dam supplies water through a network of canals to farms which grow tobacco, wheat, lucerne, fruit, and flowers.

It is also a popular holiday and weekend destination for people in Johannesburg and Pretoria due to its proximity to these cities.

For decades, water sports enthusiasts have used the dam. The TYC Yacht Club has operated at the dam since its construction in 1923.

NSRI Station 25, located at the dam, is one of only three National Sea Rescue Institute inland stations and provides a water rescue service.

However, the Hartbeespoort Dam has become so polluted and overgrown with hyacinths that it is no longer safe for water sports.

Water hyacinth, known as the world’s worst water weed, is an invasive plant that grows in polluted water and further compromises water quality.

In years gone by, the whole Hartbeespoort Dam surface was clear with no hyacinth cover at all.

However, poorly maintained wastewater treatment plants in the Hartbeespoort Dam catchment area have caused havoc with the ecosystem.

Sewage from Johannesburg and the surrounding towns flows into Hartbeespoort Dam, causing excess nutrients in the water.

This leads to an overgrowth of algae and hyacinths, harming the environment and people and animals using the water.

It has reached such concerning levels that the National Sea Rescue Institute (NSRI) has issued a warning to water sports enthusiasts.

The NSRI urgently requested boaters to refrain from attempting to navigate through the water hyacinth mats at Hartbeespoort Dam.

The water hyacinth causes a substantial danger to small craft users at Hartbeespoort dam and should never be entered by any craft.

“Under no circumstances should boaters try to navigate through the water hyacinth. By doing this, they are risking their lives,” it said.

Rescuing people in boats entrapped by water hyacinths is a complex operation and will not be necessary if people do not enter the water hyacinth mats.

In November 2024, the DA highlighted that untreated sewage continues to flow directly into Swartspruit, ultimately contaminating the Hartbeespoort Dam.

“The DA alerted the Deputy Minister of Water and Sanitation to the severe risk of untreated sewage spilling into Swartspruit,” it said.

The DA bemoaned the ongoing neglect, saying Hartbeespoort residents continued to bear the brunt of administrative failure.

The images below, courtesy of Chris Hart, the NSRI, and Yusuf Abramjee, show the problems at the Hartbeespoort Dam.

Hartbeespoort Dam covered with hyacinths