The catchment of the Okavango River extends over three countries and two hydro-climatic zones in Southern Africa, from the dry sub-humid headwaters in the central highlands of Angola over the semi-arid Kavango region in northern Namibia to its semi-arid inland delta region in Botswana. For flora, fauna and not the least the human population, the river system is a reliable source of livelihood in an environment otherwise characterized by very limited water supply. An increasing population growth exerts direct pressure on this resource by abstraction for human consumption, irrigation purposes or livestock farming, whereas indirect pressure effects due to change of land use cause modifications of the hydrological cycle.