oa Civil Engineering = Siviele Ingenieurswese - The national water management strategy
The greater part of South Africa is semi-arid, having a mean annual rainfall of 500 mm, which is only 60 per cent of the world average. River flow is poorly distributed relative to areas experiencing economic growth. Hydrological extremes, in the form of droughts and floods, are common. Over large areas the limited ground water is saline. Transported sediment deposited in storage dams reduces their combined capacity by the equivalent of a medium-sized reservoir each year. Incremental investments in dam development show diminishing returns because of factors such as long carry-over periods under high evaporation rates, increasing salination and the need for longer transmission lines and high pumping heads. Accordingly, unit costs of supply are expected to rise. Against this background, the populations of the less modern sector of South Africa as well as of several neighbouring states are increasing rapidly, while the developed economy requires increasing assurance of water supply and higher quality. Water is already scarce in many parts of the country and shortages have become critical during droughts. Augmentation of water schemes involves large capital investments and in most cases international co-operation.
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