Cape Town - The City of Cape Town is in the process of sludge removal from the Rondevlei wetland in the False Bay Nature Reserve.
The removal of the organic sludge is expected to significantly improve the health of the Rondevlei wetland system, which is still closed for recreational use.
Deputy mayor Eddie Andrews said the sludge is a very fine sediment that consists mainly of old organic matter such as dead reeds, algae and pondweed but heavy metals and plastic waste, washed in by stormwater runoff and trapped in the dead organic matter, could also be present.
“High nutrients have a negative impact on wetlands because all of the special indigenous organisms in our wetland systems are adapted to low nutrient conditions. Thus, by removing the organic sludge the City is improving the overall health, biodiversity, and water quality of the wetland,” Andrews said.
Low water levels are expected for Western Cape wetlands in the summer due to the climate, however Rondevlei remains full for most of the year.
Following the sludge removal process which started on January 5, the sluice gates at Rondevlei will be opened and allowed to drain leaving most of Rondevlei to dry out over the next four months.
Cape Town’s recreational water bodies are all situated on the flatter bottom sections of inflowing rivers which aggravates sludge build-up. With the sludge removed, the outflow from Rondevlei will be significantly better.
“By facilitating an effective drawdown, we replicate a natural system where the wetland should have a low water level during the summer months when Cape Town has little rainfall. Once the water level has lowered, wading bird species that migrate to Southern Africa in the summer months will feed along the shallow shorelines,” Andrews said.
After the vlei is dry, work will begin to remove the water hyacinth, a schedule one alien invasive species which prevents animals from accessing their habitat.