In line with a short-term agreement with the Department of Water Affairs, iSimangaliso Authority and Ezemvelo KZN Wildlife breached the mouth of the Mfolozi River over the past weekend.
iSimangaliso Authority chief executive Andrew Zaloumis said although the step had been taken reluctantly, the agreement with Water Affairs required them to breach the mouth when water levels reached 1.4GMSL (geodetic mean sea level) to mitigate back-flooding on the lower- lying farms on the Mfolozi flood plain.
The agreement also requires the department to request farmers to take necessary measures to reduce the impact of back-flooding.
“The iSimangaliso Authority, together with Ezemvelo KZN Wildlife, is addressing the critical need for fresh water in St Lucia Lake. Our objective is to reinstate St Lucia as a functional estuary as the restoration of plant and animal life will be of benefit to all users of the 70km long system. Water from the Mfolozi catchment area is essential for this to occur.”
Due to the natural closing of the mouth, fresh water has been flowing from the Mfolozi through the “Narrows” and into St Lucia Lake which has resulted in salinity levels, particularly in the southern part of the lake and estuary, dropping to below those of natural sea water for the first time in many years.
This is significant in the light of recently completed hydrological modelling which indicates that without flows from the Mfolozi River, the probability of the St Lucia mouth opening naturally is very low. Researchers include park staff as well as eminent South African hydrologists and ecologists, and a team of researchers from the Technical University of Delft in Holland.
Zaloumis added that the park had already introduced several measures to improve water levels in the estuary in order to restore estuarine function, including the recent establishment and widening of a second back channel, which had almost tripled the flows from the Mfolozi into the Narrows of the estuary when the Mfolozi mouth was closed. The measures are based on comprehensive research and monitoring of the lake system and estuary spanning about 40 years.
Technical investigations commissioned by iSimangaliso, supported by new scientific work which shows that silt does not pose the environmental risk previously thought, are also nearing completion and will allow for the full flow of the Mfolozi River directly into the St Lucia Estuary through a front channel during this rainy season.
However, Zaloumis said the perceived resistance of some sugar cane farmers to support the park in its attempt to save St Lucia Lake was of concern.
“Despite repeated requests by the iSimangaliso Authority, over a period of years, some farmers with cultivated lands within the tidal flood plain have yet to take adequate and functional measures to mitigate flooding, and remain totally reliant on artificial interventions. This problem has been exacerbated as some of these areas have slumped by a metre over the past few decades.”
However, he said they believed there was a way to assist the farmers without compromising the rehabilitation of the lake system.