Water tests show Hartbeespoort Dam is in serious trouble

High levels of suspended solids can seriously impact aquatic life, and disease resistance in fish and alter or destroy habitats.

Recent independent water tests in the Hartbeespoort Dam found very high levels of suspended solids counts threatening aquatic life and drinking water quality.

The tests were performed two weeks ago by Rotary Brits Hartbeespoort and the Wildlife and Environment Society of South Africa (WESSA) Northern Areas at nine points on the dam.

The surface water sampling was undertaken about 60 cm below the surface where there are stable conditions with minimal contamination except for small patches of Hyacinth although the Salvinia is starting to grow rapidly.

The base of the Harties reservoir tells the real story as the sampling points indicate. The depth of the sludge in three zones varies from zero to three meters thick where tested.

This is an indication of the state of the reservoir/dam.

“Total Suspended Solids (TSS mg/L) were a startling revelation, with the dam in serious trouble. A baseline reading of less than 50mg\L is optimal for all forms of life.

“High TSS levels in water bodies like dams can have several adverse environmental and ecological consequences. At Hartbeespoort Dam, the Leeuspruit inlet is the worst contaminated area in the dam at 2964mg\L and Xanadu at the R511 bridge at 6918mg/L.

“Fortunately, this is filtered out by the extensive reed bed and hyacinth below Birdwood estate resulting in a reading of 24mg\L midway in the Ifafi\Meerhof bird sanctuary, making it the cleanest water entering the dam,” said John Wesson of WESSA.

Such high readings have serious consequences such as:

  • Aquatic health: TSS can clog the gills of fish, impeding their ability to breathe and filter feed.
  • Visibility Reduction: Increased TSS reduces visibility, making it difficult for aquatic predators to locate prey.
  • Photosynthesis Inhibition: High TSS levels decrease light penetration, affecting the ability of submerged aquatic plants to photosynthesize. This can reduce the biomass and growth rates of these plants.
  • Disease Resistance: Elevated TSS can reduce fish resistance to disease and alter egg and larval development.
  • Temperature Increase: TSS can raise water temperatures by absorbing more heat, which can further stress aquatic life.
  • Dissolved Oxygen Reduction: Higher temperatures and reduced light penetration can decrease dissolved oxygen levels, essential for aquatic life.
  • Sedimentation\ Habitat Alteration: Solids that settle out as bottom deposits contribute to sedimentation, which can alter and eventually destroy habitats for fish and bottom-dwelling organisms.
  • Water Treatment Interference: In drinking water treatment, particles such as nutrients and metals can interfere with disinfection processes by blocking UV rays from reaching microorganisms.

“Therefore, maintaining optimal TSS levels is crucial for the health of aquatic ecosystems and water quality for various uses. Regular monitoring and management practices are necessary to mitigate the potential negative impacts of high TSS levels,” Wesson said.

Other concerns raised by the tests include high levels of phosphates and Chemical Oxygen Demand (COD) in some areas.

“A COD of 50mg/L is considered good for aquatic life and recreational purposes. The COD is a critical water quality parameter that measures the amount of oxygen required to chemically oxidize organic compounds in water.

“The COD in the dam ranged on the surface from 35.03mg/L to 1276.00mg/L at the base recorded at the Leeuspruit inlet where it enters the dam between Oberon and Eagles Landing \Pecanwood and 1363.26 at the Xanadu bridge on the R511 where its exit’s Xanadu Nature Estate.

“High COD levels in dam water could indicate potential environmental issues, as they suggest high concentrations of organic pollutants that could lead to oxygen depletion in the water body. This depletion can harm aquatic ecosystems, making COD an important parameter for monitoring water quality and managing water treatment processes,” said Wesson.

Phosphates as PO4 mg/L ranged from 0.01 to 16.84 at Leeuspruit and 14.36 at Xanadu Bridge. Readings are in the range of 2 mg/L. Less than 0.1mg/L prevents algal growth.

Wessa and the Brits-Hartebeespoort Rotary Club thanked everyone who donated towards the project.


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