Meet “Otter”, the new weed harvester launched at Rietvlei waterbody last Thursday 9 May, a major boost for the environment and the cause of many a bright smile for conservationists.Otter’s job is to remove water weeds like hyacinth and water lettuce from waterbodies in an environmentally responsible manner.
Mayor Geordin Hill-Lewis and Eddie Andrews, Mayco member for spatial planning and environment, were on hand for the maiden voyage of the vessel last week. This is the second of three new specialised vessels that the City is delivering for recreational vleis, following Zandvlei’s weed harvester delivery in December 2023, with a second vessel for that vlei scheduled for 2025.
A weed harvester is a specialised vessel with blades underneath for the cutting of weeds. It is equipped to cut, gather, and remove weeds to improve water quality and assist recreational users. However, some algae are critical to the functioning of the vlei, thus, it is important to also keep these areas where weed is not harvested.
TygerBurger previously reported (“Rietvlei woes continue: Water sport athletes demand City fix ‘mess’,” 1 March 2023) of several past pollution spills at Rietvlei waterbody. The waterbody had to be closed numerous times due to a highly toxic blue-green algal bloom found in the water. In June 2020 a large spill occurred – high levels of e.Coli were recorded resulting in the closure of the vlei to all water activities.
This was due to the ingress of sewage water into the stormwater system, leaks, failed equipment, load shedding, and a total lack of the City’s engagement and accountability.However, with Otter now safeguarding the vlei, activists hope this will improve the water quality.
Caroline Marx, a conservationist in the Table View and Milnerton area, says this is part of a long-term plan including reducing the amount of nutrients entering the wetlands from sewage spills, agricultural runoff, etc aimed at controlling these alien invasive plants. “Elsewhere such as the Vaal Dam, authorities have resorted to spraying the environmentally toxic and possibly carcinogenic herbicide Glyphosphate into the drinking water resource of millions of people without effectively addressing the underlying causes or long-term control,” Marx says.
What Otter will be used for
In Rietvlei in particular, the weed harvester is used to cut Sago Pondweed and also to remove algae build-up. This not only improves the environmental health of the wetland by removing excess nutrients but makes the vlei more navigable and safer for watercraft and all of the communities who use this vlei.Following a public naming process, Rietvlei’s new weed harvester has been named “Otter”, while the recently delivered Zandvlei weed harvester was named the “Cape Shoveler” after an aquatic bird species.
The City says they have pledged to improve the water quality and management of recreational vleis, “and we are pleased to reach another milestone with the delivery of this latest weed harvester at Rietvlei, which closely follows the delivery of Zandvlei’s first harvester late last year.
These specialised vessels will go a long way to boosting the environmental health at both Rietvlei and Zandvlei. This will also be of major benefit to the thriving local economies around these vleis,” says Andrews.Rietvlei is situated in the Table Bay Nature Reserve and is a popular recreational waterbody.
“I am confident that the addition of the Otter weed harvester will make a significant impact in improving the water quality. It was wonderful seeing this impressive vessel taking to the vlei,” he adds.
Budget
The Spatial Planning and Environment Directorate proposes to spend around R408 million for the rehabilitation of vleis in the city, including the river wardens job creation programme, water quality improvement programmes at Rietvlei, Zeekoevlei, Milnerton Lagoon and Zandvlei, the lowering of the weir at Zeekoevlei, and the procurement of a third brand new weed harvester for Zandvlei over the next three financial years.
“To ensure on-time delivery, the City’s Fleet Management Department has closely monitored the production of this highly specialised vessel, which was proudly manufactured right here in Cape Town,” says Mayco member for corporate services, Theresa Uys.
Weed harvesting at Rietvlei focuses on the macrophyte Stuckenia pectinata or Sago Pondweed. Urban systems are frequently subject to increased nutrient loading, or eutrophication, and the Sago Pondweed absorbs some of these excess nutrients; however once the pondweed dies the nutrients are released back into the vlei, and pondweed reduction is implemented to assist in mitigation.
