At the present stage in developing countries, key environmental challenges tend to be closely linked to sustained economic development and improved human livelihoods (IUCN ROSA, 2002) threatening sustainable use of natural resources and conservation of biological diversity. In addressing the particular challenges in developing countries, adequate attention has also to be paid to fundamental hydro-climatic differences between the tropics where they tend to be located and the temperate zone hosting many of the industrialized countries (Falkenmark and Chapman, 1989; Ayebotele and Falkenmark, 1992). The main factors of importance here is the much larger rainfall variability and the much larger evaporative demand.