Investigations conducted by the Department of Water and Sanitation (DWS) have indicated that the fish deaths that occurred at the Hartbeespoort dam on Tuesday, 11 April 2023, were due to extremely low oxygen levels in the dam.
The incident of fish deaths was uncovered at the Ifafi Aquatic Club and the Schoemansville Oewer, near Ifafi, at the Hartbeespoort dam.
Samples were taken at four different sites of the dam including at the dam edge near the overgrown hyacinth, at 60 metres away from the edges of the dam, at the Ifafi Aquatic Club jetty as well as where the fish deaths occurred near the Ifafi Aquatic Club, to determine the cause.
The results revealed that excessive algal growth caused by high nutrient (phosphorus and nitrogen contents) levels in the water led to oxygen depletion and fish mortality. This occurrence of low concentration of oxygen in water is typical in sewage-contaminated systems with high organic matter and could not be attributed to high water temperatures given the average temperature of 22 º C at the time of sampling.
To address the Hyacinth and algal growth at the dam, the DWS has recently appointed Magalies Water for a period of three years, to develop and implement a programme that will deal with the invasive plant and the algae that infesting the dam.
The entity is expected to develop a resource management and remediation plan to address the poor water quality and minimise and control the plant and algal growth in the dam and the upstream catchment which lead to its pollution and compromise water quality and use of the dam.
Part of the scope for Magalies Water is to develop a short-term intervention plan to remove the hyacinth, review the algal management strategy and develop a catchment management plan to address the receiving of water into the dam from the upper catchment.
The plan will also involve the repurposing and readapting of the Metsi a Me programme to focus on the upper catchment which is contributing to the eutrophication of the dam.
The programme is expected to start by mid-May and will incorporate the Biological Control Programme managed by the Department of Forestry, Fisheries and Environment (DFFE).