(1) The Department of Water and Sanitation (DWS) has taken steps to address the invasive hyacinth plant in the Hartbeespoort Dam.
(1)(a) Magalies Water Board is the implementation agent for the remediation of the dam. The Dam’s catchment area comprises of the metropolitan areas of Ekurhuleni, Tshwane and Johannesburg and this water is mostly polluted by urban runoff and wastewater effluent, though there are industrial and mine water discharges as well.
Three measures have been implemented to control Hyacinth namely biological control, herbicide application, physical removal or a combination of these. Under the guidance and supervision of Rhodes University and with assistance from the community around the dam, biological control in the form of Megamelus scutellaris (an insect that thrives on a diet of water hyacinth) is being implemented. These are mass-reared and released every year to prevent the plant from flowering (producing more seeds) and progressively kill the plant.
Magalies Water has appointed subcontractors to compliment the biological control through the mechanical and manual removal of water hyacinth. Harvesters, excavators and TLBs are utilised to remove the hyacinth mechanically, while the manual removal is done by employees.
DWS conducts compliance and enforcement activities in the catchment area focussing on some of the largest users authorised for discharge as well as unlawful activities such as chrome washing operations. The effluent from wastewater plants owned and operated by municipalities within the catchment area remain a challenge. A catchment initiative to form collaboration between the metropolitan municipalities is underway.
(1)(b) Hyacinths has been on the dam since the 1960s. A single flowering hyacinth can produce up to 3000 seeds. These seeds can remain viable for more than 5 years. As a result of the poor water quality and the seeds that have been deposited over the years, the seeds germinate and grow very well (the plant has the ability to double its mass within 5-10 days) in nutrient rich water. It will take several years to see a reduction in the hyacinth on Hartbeespoort dam due to the buildup of this seedbank and the water quality. The main cause of the current growth is the extreme weather conditions experienced in October/ November 2024 that led to decreased dam levels which in turn exposed the hyacinth seeds to conditions that are conducive for germination. These weather conditions also led to the accumulation of nutrients upstream of the dam, which were subsequently washed into the dam during the rainy season experienced in December 2024 and January 2025. These factors promoted a high re-growth rate of water hyacinth.
(1)(c) The current level of infestation is 33.84% of the surface of the dam. These plants are not rooted and float around the dam depending on the strength and direction of the wind which also makes removal a challenge.
(1)(d) As long as the water hyacinth is being continuously fed with nutrients from upstream activities and around the dam, high infestations will continue. However, had there been no controls at all, then the infestation will be at >70%. The efforts made by the DWS to some extent mitigated the water hyacinth infestation.
(1)(e) The plants contribute to higher loss of water in the dam due to evapotranspiration from the plant mass. The plants do not significantly absorb/remove the nutrients in the dam. The plants together with the effluent flowing into the dam reduce the available oxygen in the water. The hyacinth has negatively affected tourism activities specifically boating and recreational activities around the dam.
2. The Minister will respond on this matter, and any other matter related to the DWS mandate, if/as requested to do so.
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