The regional limnology of southern Africa

Abstract

The geomorphological, geochemical and climatological features of southern Africa define five limnological regions of the subcontinent. They are, from east to west: (Fig. 4.1a & b)

• 1. A subtropical coastal peneplain in which the marine influence is strong resulting in coastal lagoons of varying salinity and subsoil water with an elevated salinity.

• 2. The summer rainfall region of the elevated plateau and south eastern coastal plain with both temporary and permanent surface water with total dissolved solids (TDS) less than 500 mg l^-1, alkaline pH varying between 7.5 and 9.

• 3. The elevated mountain massif of Lesotho, the so-called austral-montane region with surface water TDS concentration of 47–273 mg l^-1, pH 6.6–8.4 (pH higher than 7.5 in lowland streams).

• 4. The temperate acid waters of the Western Cape arising principally from the Table Mountain Sandstone in the mountainous regions, but at lower levels variously influenced by cyclical salts of marine origin, which increase buffering capacity so that pH may increase to neutrality.

• 5. The arid west stretching northwards from inland of Port Elizabeth into Namibia and southern Botswana. Surface water temporary, high TDS and alkaline pH.