Zandvlei’s old weed harvester is missing in action and plans to take delivery of a new one by June have gone up in smoke.
Without a weed harvester, the vlei risks becoming choked with fast-growing pondweed that will clog up the waterways and cause a stench when it rots, says environmental scientist David Bristow.
Dr Bristow is chairman of the Zandvlei Trust, a volunteer group of residents who live around vlei, and a member of the Zandvlei Protected Area Advisory Committee (ZPAAC).
He said the harvester, known as Kingfisher, was more than a decade old and had been out of commission repeatedly and for lengthy stretches since last summer.
“According to the operators, there are no parts available, and it’s being kept together with old tights and chewing gum. This past summer it worked for a few days and was then out of action for weeks.”
Save the Zandvlei petitioner Mike Ryder said the City had been expected to take delivery of a new weed harvester in August last year, but that had been stretched to December and then early this year (“Zandvlei petitioners still waiting for City response”, Echo, May 13, 2021).
The deputy chair of the mayoral advisory committee on water quality in wetlands and waterways, Alex Lansdowne, said it had emerged during a meeting with City officials, ZPAAC and councillor Aimee Kuhl, on Wednesday May 25, that the delivery of the new harvester, scheduled for June, would no longer happen.
“The reasons for this are under investigation,” he said. “There are legal reasons why detailed information cannot be given at this stage.”
Instead, the City advertised a new tender on Friday May 27.
“Weed harvesters are not readily available in South Africa and must be built from scratch. However, the City is forced by regulations to procure locally,” he said.
Ms Kuhl and Zandvlei reserve manager, Kyran Wright are to report back monthly to ZPAAC on the new weed-harvester contract.
Mr Lansdowne said ZPAAC had agreed to the current weed harvester being removed from the vlei for repair and maintenance to ensure compliance with SA Maritime Safety Authority requirements.
Dr Kevin Winter of UCT’s Water Institute said the weed harvester was a band aid for a much bigger problem: elevated levels of nutrients, from pollution, entering the vlei and fuelling excessive weed growth.
“Weed harvesting is treating the symptoms of nutrient discharge into the vlei from poor catchment management and failing sewerage and sewage systems.
“Since the vlei serves multiple purposes and is an amenity that has recreational value, it’s important to manage the system, and weed clearing is part of that management. However, what is needed, even more so than a weed harvester, is demonstrable action in the catchment to deal with pollution sources and failing sewer pumps that allow sewage to spill into the waterways that are polluting the vlei,” said Dr Winter, who is part of mayor Geordin Hill-Lewis’s water advisory committee to deal with the city’s water pollution and sewage woes.
Mr Wright said that apart from sewage spills, fertiliser run-off from Westlake and Steenberg golf courses, the Pollsmoor food farm and Constantia wine farms and pool backwashing from suburban gardens were also causing the spread of pondweed.
Letitia Mathieson, the assistant to mayoral committee member for spatial planning and environment Eddie Andrews, said the City planned to acquire three new weed harvesters over the next two years.
In meantime, the City’s Expanded Public Works Programme teams would remove weeds by hand from August to reduce the impact of weeds on the vlei, she said.
The Marina Da Gama Homeowners’ Association website states that homeowners are responsible for clearing waterweed from the water within two metres of their gardens.
Stan and Jenny Gallon have been removing water lettuce, parrot feather and water hyacinth from the Keyser River and question if a weed harvester can get to the roots, which are important to remove. They say they have seen an increase of pondweed types in the river that runs past their garden in Frogmore Estate in Steenberg over the past few years.