Cape Town proposes modification of weirs at Zeekoevlei and Rondevlei

The City of Cape Town proposes the redevelopment and upgrade of the weirs at Zeekoevlei and Rondevlei that are located within the False Bay Nature Reserve.

The proposed redevelopment of the ‘weir complex’ is to supplement other medium-term interventions, including the dredging of Zeekoevlei, to improve the overall water quality of this Ramsar site. 

Both Zeekoevlei and Rondevlei are managed by a system of penstock sluice gates to allow for the water level to be dropped to a minimum depth, which is known as the annual ‘drawdown’, usually at the end of the summer sailing season.

The intention of the drawdown is to remove nutrient-rich water and sediment from the system, and to increase the capacity of the vleis prior to the winter rainfall season to reduce the risk of flooding of surrounding areas.

Benefits of proposed modification

• The proposed redevelopment and modification of the weirs will allow deeper and more flexible annual drawdowns of the Zeekoevlei and Rondevlei to facilitate sludge and reed clearing, and oxygenation of exposed sludge,

• The new design will allow for a deeper drawdown level, which will assist significantly with the improvement of the water quality of the vleis,
• The new Rondevlei weir will allow for a raised groundwater table in the southern portion of the nature reserve section,
• It will allow for much more flexibility, and the movement of natural estuarine fish into the vleis.