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The South African coastline stretches for some 3000 km from the Gariep (Orange) River at the Namibian border in the west to Kosi Bay near the Mozambique border in the east. Some 300 river outlets intersect this coastline and these range from small water bodies which are only occasionally connected to the ocean, to large, permanently open systems, and coastal lakes connected to the sea via a narrow channel. Being places where rivers meet the sea, estuaries are one of the most important features of the South African coastline; they are tranquil areas of high productivity and play a vital role in the life cycles of many plants and animals.
Apart from their ecological importance, estuaries are also popular sites for recreational, tourism and residential development. The protected coastal waters of estuaries are also used for industrial and harbour development as well as domestic and industrial effluent discharges. Population growth and development in the coastal zone is placing increasing pressure on the health and function of these ecosystems.
Estuaries are an irreplaceable natural resource that must be managed carefully for the mutual benefit of all who enjoy and depend on them. In order to manage this diversity of uses so that sustainable utilisation of these resources is practised, the Department of Environmental Affairs & Tourism: Directorate Environmental Information and Reporting has recently completed an assessment of the State of South African Estuaries based on the geomorphology, fish community, water quality and aesthetics of some 250 estuaries. This also forms an important baseline against which future changes can be monitored.
In addition to coastal development pressures, activities taking place in the catchments of rivers that flow into estuaries also affect the health of these ecosystems. Water abstraction through impoundments and for irrigation for example, alter river flow patterns entering estuaries; poor agricultural practices in the catchment can also lead to increased nutrient and sediment loads while domestic and industrial waste discharge affect the water quality.
Historically, conditions in the catchments of estuaries were difficult to recognise and quantify, however the National Land-Cover Database Project (NLC), has provided a unique opportunity to assess the state of land-cover in the catchments of rivers that flow into estuaries.
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