African Water Development Report 2006 - United Nations Economic ...

Fig. 4.12: Percentage of Domestic, Agricultural and Industrial Water Use in AfricaZimbabweZambiaUgandaTunisiaTogoTanzaniaSwazilandSudanSouth AfricaSomaliaSierra LeoneSenegalRwandaNigeriaNigerNamibiaM ozambiqueM oroccoM auritiusM auritaniaM aliM alawiM adagascarLibyaLiberiaLesothoKenyaGuinea-BissauGuineaGhanaGambiaGabonEthiopiaEritreaEq. GuineaEgyptDjiboutiCôte d'IvoireCongo, DemCongoChadCape VerdeCameroonC. African RepBurundiBurkina FasoBotswanaBeninAngolaAlgeriaFRESHWATER RESOURCES IN AFRICA• • • • • • • • • •• • •• •Agric Dom IndSource: World Resources Institute – Earth Trends. The Environmental Information Portal: http://earthtrends.wri.org/Non-Conventional Water ResourcesOwing to the limited renewable water resourcesin the northern subregion, giving rise to whatis generally referred to as water resources man-0agement in drought prone areas, there is a widerecourse to harnessing non-renewable and nonconventionalsources of water.Non-renewable water resources in theNorthern SubregionNearly all surface water, e.g. those which flow inrivers, are renewed. On the other hand, a relativelygreat part of water which infiltrates intothe ground reaches depths which make it inaccessible;it is thus protected from evaporationand can be preserved even through geologicaltimes. Generally non-renewable water, knownalso as “fossil water”, is made up of very old seepagewaters under climatic and morphologicalconditions, different from current conditions,and thus out of the contemporary water cycle.Groundwater aquifers, which can be qualifiedas fossils, are not entirely fossils, because thereis always a refill; but the speed of flow betweenthe zones of refill (not very wide) and the placesof use are very slow (thousands of years). Onlyadvanced methods of analysis, particularly thoseby marking with tritium, allow distinctions tobe made between renewable waters in a scale of69