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

Figure 6.3: Water Availability and Freshwater Stress and ScarcityProtecting Ecosystems in AfricaThe total capacity of the reservoirs in Africa exceeds1000 km 3 which is about 20 per cent of thecapacity of all reservoirs in the world. In terms ofnumbers, South Africa; Morocco and Algeria haveconstructed more reservoirs than the other Africancountries, but the reservoirs in these countriesare not large; the largest reservoirs have been constructedin the countries shown in Table 6.3.Most of the reservoirs developed in Africa arefor power generation given the urgent need forcheaper energy and, also, the high hydroenergypotential of African rivers which are secondonly to Asia’s in this regard, at the world scale.The Congo and Zambezi rivers have optimumresources for power generation. Large reservoirsgreatly affect the hydrological river regimes,increasing possible use of river runoff and providingflood control. However, in a hot and dryclimate, reservoirs may greatly reduce the totalwater resources in rivers due to intense evaporationfrom water surfaces. This is very significantfor Africa where most large- and medium-sizedreservoirs have been developed in plains andon plateaus where they have considerable watersurfaces. Only the reservoirs in the countriesmentioned earlier (South Africa; Morocco andAlgeria) have been constructed in mountainous131