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A partially turbid river. Sediment-laden water moves down a slope through the normal river water. The turbidity current moves because it has a higher density than the water through which it flows
The lower uMvoti river close to and downstream of Stanger is highly polluted.
This was according to Institute of Natural Sciences principal scientist Gordon O’Brien speaking at an Amatigulu honorary rangers organised environmental talk at Simbithi Country Club on Wednesday November 12.
O’Brien said other rivers such as the Amatigulu and Thukela rivers have some localised negative impacts but are generally in an acceptable state of health.
He explained the cause of the pollution is only partially known and much work still needs to be done to pin point all of the sources.
He said there are three main causes of stress on our local river systems.
Firstly, reduced flows in rivers due to the agriculture sector, municipalities and industries extracting too much water from the rivers.
Secondly, reduced water quality from salinization from urban areas, mines and heavy industries such as paper mills pumping waste water back into the river, nutrient enrichment from poorly functioning water treatment works, metal contamination from mines and waste water treatment works, organic pollutants (for example pesticides contamination) from the agricultural sector and changes in temperature and oxygen levels.
Thirdly, changes to the structure of river eco systems (some of the greatest threats to eco system health but often overlooked).
In Ilembe, some farming practices remove the riparian buffer (interface between land and river, for example woodland or forest) between land and river, allowing too much soil to end up in the rivers, causing them to clog up and slowing down flow.
Sand mining directly affects the well-being of local rivers.
In the uMvoti river sand mining destabilises the river banks, allowing sediment to get dumped into the main stream and slowing down the flow of the river.
The river becomes shallow and heats up when sediments do not get flushed down the river, which has a massive knock-on effect in the river system.
Local sugar cane activities have also removed large parts of the riparian vegetation so that a lot of sediment is being flushed into the river.
O’Brien said there are a number of things that can be done to help heal these rivers.
Stakeholders can get actively involved in conservation and management of these ecosystems through forums, conservation groups and or independently.
O’Brien advocated that stakeholders take a look at the Water and Sanitation department’s establishment of management plans for rivers in the Ilembe district at www.dwaf.gov.za.
He stressed that these plans will direct all formal management efforts in the future and will be binding on organisations and institutions.
He added that schools and individuals can actively participate in monitoring of the health of rivers by visiting www.groundtruth.co.za and getting involved in listed projects.