Sunday, September 09, 2007

Current Conditions - Windy and dry

Wind Wind Wind....
How is it possible to experience early August in the beginning of Spring. One sure thing is the drought is still continuing. Be it Elninio or Global warming or both, this is the longest drought the Wetlands has experienced in many years.
With the mouth being opened since 09 March 2007 and the recent closure in early August we need rain urgently. All the Estuary Mouth maintenance was washed away by the tidal surge that where experienced on the Equinox. Since loads of equipment loss where suffered, the Authorities has not commenced with their systematic maintenance of the mouth.
Over the past 15 years a low human interference approached was maintained. This was minimised to a maintanace programme to keep the iMfolozi River from washing silt into the St. Lucia Estuary mouth. Whether the iMfolozi dumps it silt on the Tugela basin or right into The St. Lucia Estuary system the long term effect is still the same.
Due to soil erosion in the catchments areas of this power full river, and the decimation of the Wetlands system that acted as a sediment catchments area, the iMfolozi river carries many million tons of top soil and dump it in the vicinity of the St. Lucia Estuary mouth area. The tidal movement of the ocean and wind direction pushes the sediment into the low energy system of Lake St. Lucia, through the Estuary mouth.
Only flash floods from the five feeding rivers can clear this sediment from the Lake system. The last flash flood was in 1984. Since most of the feeding rivers are now used for Sugar cane irrigation much of the fresh water built up in the Lake system has been compromised. This has a very negative impact on the water flow out of the estuary mouth and this constitutes to the closure of the Estuary mouth naturally.
This lack of fresh water supply leads to another problem, the salt built up in the Lake System. No fresh water pushing the salt water from the top and the ever presence of evaporation lead to precious fresh water losses for the system and the salinity to raise. This built up has a negative impact on the environment, since most species are adapted to live in the Lake's saline conditions that ranges from close to and lower than sea water.
As the current situation stands with evaporation versus fresh water feed, the salinity could rise to three times that of sea water in a short period of time. God send, is the millions of pine trees that has been removed from The Eastern Shores. The impact would probably be much worse if it was not for these removals of precious water gobbling trees.
The system needs a well managed maintanace plan, a well manage water supply and loads of rain to stay the prestine world class Wetlands system it currently is.
For Africa
P.J. Viviers

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