Spring Rains for Lake St Lucia

Zululand has been enjoying some of the wettest weather in a long time, with September and October’s spring rain being the highest experience in iSimangaliso in 15 years.

In St Lucia, up to 76mm of rain was received, and water levels at the St Lucia bridge rose by 77cm since the 4th of December.

image source - iSimangaliso
image source – iSimangaliso

According to iSimangaliso,

The levels in the Narrows are now above mean sea level and there will be outflow from the system during low tides and push in during high. There is also a southward push from the lakes through to the Narrows as the lake level continues to rise and lake flow starts moving south.

“This rain is not an instant fix but the increased water levels and flows through the mouth bring us another huge step closer to the restoration of the system” says Park CEO Andrew Zaloumis.

The hotly debated and sometimes controversial interference of the uMfolozi and Lake St Lucia was set right in 2011 when iSimangaliso agreed to let the two re-join in a bid to restore the functioning of  South Africa’s largest estuarine system.

In a recent newsletter, iSimangaliso said:

 Since 1952 the uMfolozi River has been deliberately kept separate from the St Lucia system, which has reduced freshwater inflow to the system and interfered with natural mouth dynamics. The July 2012 relinking of the uMfolozi River back to the St Lucia estuarine lake system was an important first step towards the restoration of estuarine function, one of the primary aims of the GEF project.

Since the linking of the uMfolozi back to St Lucia in early July 2012 water levels in the system have risen substantially as a result of catchment inputs and direct rainfall. As a direct result of the linkage of the uMfolozi to the system water levels in the Narrows (the 20km channel linking the lakes to the sea) lifted by 20cm.

This resulted in northward flow from the Narrows into the lakes. Since then high rainfall and inputs from all the river catchments have added to this raising water levels. This raised water levels to the base of the previously exposed gauge plate at Charters Creek and since the 1 October 2012 this gauge has registered a further 60 cm rise as measured on 26 November 2012.

The combination of the rise in water level to the gauge plate and the rise registered on the ruled gauge plate means that lake levels have risen by at least 80 cm. Since then levels have risen further and it is likely that a rise of at least 1m across the lake has occurred.

This is also easily seen in the change in the water body from a shallow veneer of water (on average approximately 10-15 cm deep) covering the more central portions of the lake to a wide connected water body which has moved much closer to the original shorelines of higher water levels. Analysis of satellite imagery when it becomes available will allow us to quantify what this means in percentage change of the lake’s water surface area.


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