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Restoring Lake St Lucia Estuary

Restoring Lake St Lucia Estuary

Feb 2017

The iSimangaliso Wetland Park has signed two contracts of R23.41 million each with T&T Marine (Pty) Ltd and Scribante Africa Mining (Pty) Ltd. Both contracts will run until the end of June 2017 and are for the loading, hauling, tipping and disposal of sand from the dredge spoil island in the mouth area of the Lake St Lucia Estuary. This brings the total value of iSimangaliso’s  restoration project to R61.82 million.   

The existing Phase A (see diagram below) contractor, Cyclone Engineering Projects (Pty) Ltd, has received a contract extension for R5 million, in addition to their current contract of R10 million. This will take their work to the end of January 2017 to completion, so there will be three contractors on site in January, and two from February to June 2017.

Quantity surveyors have confirmed that to date, 96 842 cubic metres of dredge spoil have been removed and with Phase B (see diagram below) a total of 1.2 million cubic metres are expected to have been removed by the end of June.  Phase B contractors, T&T Marine (Pty) Ltd and Scribante Africa Mining (Pty) Ltd, have begun work on site. 

This removal of material has begun to reverse the negative impacts of dredge spoil deposition, enhancing the hydrological and ecological functioning of the 350km2 Lake St Lucia estuarine system, Africa’s largest.

“It is early days, but nature’s healing has begun. On the back of improved flows from the uMfolozi River, Lake St Lucia’s water levels have improved from 10% water coverage in early 2016 and have remained at 90% since November 2016, while salinities remain fresh,” says Andrew Zaloumis, CEO of iSimangaliso.  “This is South Africa’s largest and ecologically most important wetland rehabilitation project.  The appointment of more than one contractor aims to expedite this work, improve efficiencies and optimises the money spent.”

Derek Stretch, Professor of Hydraulics & Environmental Fluid Mechanics School of Engineering, University of KwaZulu-Natal, confirms that the work to remove the dredge spoil is significant:  “It enables us to reverse some of the negative impacts of decades of dumping dredge spoil in that area and facilitates the more natural functioning of the Lake St Lucia Estuary.”

Prof Stretch was one of the researchers providing scientific information that led to the change in the management strategy of the Lake St Lucia system. A large body of research work now underpins iSimangaliso’s restoration project funded by the World Bank’s Global Environment Facility. For decades it was believed that silt was the biggest risk to the system.  Prof Stretch’s work challenged this – silt is an issue, but the critical issue is fresh water and the uMfolozi River’s ability to act as the powerhouse that drives the natural process of the mouth.

“While the first part of the restoration work is underway, we are very likely in a sediment accumulation phase,” says Stretch. “We are still in a drought and the Estuary mouth is still closed to the sea. This is however only the short-term view, because once we enter a period with more rainfall – floods and tidal flushing associated with an open mouth will result in a net loss of silt from the Estuary.”

While the probe readings and Landsat images (see above) confirm that water levels reached at the end of November have been maintained, January looks equally as promising. The following rainfalls were recorded over 48 hours during January 2017:

Kosi Bay – 60mm
uMkhuze – 14mm 
False Bay – 40mm
Charters Creek – 20mm 
St Lucia – 31mm 
Mission Rocks – 26mm  

With 90% of the Lake's surface area now covered, the Lake is once again a single body of water no longer compartmentalised, and joined via the Narrows to the mouth. The status quo remains. 

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