Introduction to surface water
Southern Africa currently experiences a highly variable climate which ranges from desert and semi-desert regions in the west of the country to humid, sub-tropical regions along the wetter eastern seaboard of the country.
The mean annual precipitation (MAP) for the country of 450 mm per annum is below the world average of 860 mm per annum, with the potential evaporation being greater than rainfall in many areas (Figure 1). Thus, South Africa’s water resources are naturally limited and unevenly distributed.
Natural river flow has been significantly altered -- both in quantity and quality -- through the construction of reservoirs, inter-basin transfers, and domestic, industrial and agricultural water use. Additionally, changes from the natural land cover to anthropogenic land uses such as urban areas, commercial forestry and agricultural lands to meet human demands for food, fuel and fibre have significant impacts on the water resources of the country.
South Africa’s water resources have been highly developed and utilised, and in many instances over-exploited. Of the 19 water management areas in South Africa, 10 are currently water stressed (NWRS, 2004). Continued population growth, growing urban areas and economic development, and continued degradation of our natural resource base will place further pressure on water resources.