Thanks to recent rains, satellite images taken this week of Lake St Lucia – Africa’s largest estuarine lake and the world’s oldest estuary – tell a positive story.
The system’s water levels have increased dramatically, resulting in strong flows from the Umfolozi River into Lake St Lucia.
With 90% of the surface now covered, the system is once again a single body of water, no longer compartmentalised and joined through the narrows to the mouth.
In February, only 10% of the surface of the lake was covered with water.
The water now flowing into the system from the Umfolozi River has caused the levels in the narrows to rise to 1.2m above mean sea level – the highest recorded in a long time.
The direct rainfall and flow from other rivers, such as the Umkhuze, Umzinene, Hluhluwe and Nyalazi, is also providing much-needed relief to the northern sections of the lake.
Salinity levels throughout the system are now below five parts per thousand (ppt) – sea water is around 35 ppt – with the freshest water found in the southern sections, where millions of litres continue to pour in from the Umfolozi River.
“While this is excellent news for the system, we’re still not out of the woods and more rain is needed, especially in the catchment
areas,” iSimangaliso Wetland Park Authority CEO Andrew Zaloumis said.
The dramatic increase in the lake’s water levels is partly due to the heavy rains along the local eastern coastal belt and the restoration project presently underway.
In January, iSimangaliso signed a R10-million contract with Cyclone Engineering Projects to remove 100 000m3 of dredge spoil obstructing the natural course of the Umfolozi River.
The work has progressed slower than anticipated due to technical problems associated with, among other things, the drought brought on by the lowest rainfall levels in 65 years.
iSimangaliso has also raised additional funding for the hydrological restoration of the Lake St Lucia system. A tender has been advertised for a second service provider to expedite the removal of dredge spoil.
With work continuing through December and January, it is anticipated the first phase of rehabilitation will be completed at the end of January.
A second phase will continue for 12 more months.
“Our estuaries, with their surrounding wetlands, comprise some of the most productive, yet threatened, ecosystems in the world and the health of the Lake St Lucia ecosystem is directly linked to the livelihoods of people in the area – in terms of tourism and harvesting of raw materials,” Zaloumis said.
“Lake St Lucia takes centre stage as one of the most beautiful and ecologically important assets of the iSimangaliso Wetland Park and it’s thanks to funding by the Global Environment Facility, which realises its global significance and its significance locally that the lake’s rehabilitation solution is making progress.”
Over a period of close to 60 years, dredge spoil was artificially deposited in the natural course of the Umfolozi River in an attempt to limit its inflows into the Lake St Lucia estuary.
This was done in the belief that the estuary would be protected from silt. The process reduced freshwater to Lake St Lucia from the Umfolozi River.
The Umfolozi River is the largest of the five rivers entering the system and accounts for 60% of the freshwater inflows into Lake St Lucia’s system.
It is also the powerhouse driving the natural process of the mouth, limiting inflows and narrowing the river course by artificial means.
The results of the scientific research recommended the Umfolozi should be allowed to pursue its natural path into the estuary.
This necessitated the removal of dredge spoil so the Umfolozi could once again take its place as the contributor of the major part of the lake’s fresh water.