Types of rivers and their characteristics

Abstract

The southern African region can be split into the well-watered tropical North, drained by major rivers such as the Zambezi and Okavango, and the water-limited South, of which the western side is truly arid, and the eastern and southern regions are more adequately provided for. Fig. 3.3 in Chapter 3 summarizes the rainfall of the region. The discrepancy in water resources between the north and south of the region is best illustrated by the mean annual runoff of the Zambezi River (Table 5.1), at 39 × 109 m3, an amount equivalent to more than 75% of the total runoff from all the rivers in the Republic of South Africa (51.5 × 109 m3 according to Hattingh 1981). The great majority of southern Africa’s water resources are riverine. South of the Zambezi there are very few natural freshwater lakes. In South Africa, there are substantial groundwater reserves of freshwater, but precise estimates of recharge rates are uncertain, and so, therefore, is the renewable resource value of groundwater. Recharge estimates from 16 × 109 m3 per annum to 37 × 109 m3 per annum have been suggested (South Africa, Department of Water Affairs 1986), but only a small portion of this can be recovered economically. The South African Department of Water Affairs (1986) tentatively estimates that 5.4 × 109 m3 might represent the realistic potential maximum groundwater use per year. This represents 16.4% of the annual exploitable surface runoff from rivers.