Meet 'Otter', Cape Town’s new weed harvester to manage Rietvlei

Clarence Ford speaks to Barbara Friedman about what's trending online.

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The City of Cape Town has a new, specialised weed harvester for Rietvlei.

Mayor Geordin Hill-Lewis and Deputy Mayor Eddie Andrews were on hand for the vessel's maiden voyage (on 9 May 2024).

"I love to see news about our waterways in Cape Town... to see that they are being kept in the best condition and are as environmentally healthy as possible for both users and the animals."

- Barbara Friedman

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 that cut 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 keep these areas where weed is not harvested.

In Rietvlei, the weed harvester is used to cut Sago Pondweed and 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.

The City says 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. The weed harvester also collects floating filamentous algal mats which can accumulate on the water surface in summer months.

Andrews says Cape Town intends to spend around R408 million to rehabilitate vleis over the next three financial years.

These rehabilitation initiatives include:

• River Warden job creation programme
• Water quality improvement programmes at Rietvlei
• Zeekoevlei, Milnerton Lagoon and Zandvlei
• Lowering the weir at Zeekoevlei
• Procurement of a third brand-new weed harvester for Zandvlei.

"I am confident that the addition of the Otter weed harvester will make a significant impact in improving the water quality."

- Eddie Andrews, Deputy Mayor - City of Cape Town

Scroll up to the audio player to listen to the full conversation.