Hydrology of low latitude Southern Hemisphere land masses

Abstract

Low latitude southern continental areas are characterized by exposure to high solar radiation and the climatic influence of southward moving warm ocean currents along their eastern coasts together with cool, northward-moving currents on their west coasts. Steep climatic gradients exist from the generally wet eastern coasts to the semi-arid and desert regions of the west. The variability of annual rainfall in both time and space increases with increasing aridity, due to the decrease in influence of reliable precipitation mechanisms and an increased reliance on convective rainfall producing mechanisms. Groundwater resources are more limited and greater reliance must be placed on surface waters for urban, industrial and agricultural purposes. Irrigation is the major water use, thereby adding to the load placed on limited surface resources and accelerating depletion rates. Surface runoff per unit area falls with increase in aridity due to the combined effects of lowered volume and raised rainfall variability plus increases in evaporation from both land surfaces and vegetation. Typically, river flows vary over a wide range from year to year, and in desert areas from hour to hour.