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Preface Annex 1
OVERVIEW OF RESOURCES
Africa’s extreme variability of rainfall – in time and space – is reflected in an uneven distribution of surface and groundwater resources, from areas of severe aridity with limited freshwater resources like the Sahara and Kalahari deserts in the northern and southern parts, to the tropical belt of mid-Africa with abundant freshwater resources.
Internal renewable freshwater resources average about 3 950 km³ per year, as shown in Table 1. This amounts to about 10 per cent of the freshwater resources available globally and closely resembles Africa’s share of the world population at 12 per cent (Donkor 2003).
There are over 50 internationally shared river and lake basins in Africa. Figure 1 shows the major river basins. These are the Niger, Lake Chad, Nile, Zambezi and Orange river basins. Most of the surface water resources are concentrated in the Congo, Niger, Ogooue, Zambezi and Nile. Less than 10 per cent of Africa’s river and lake basins are covered by wetlands (IUCN and others 2003). Nevertheless, wetlands are an essential part of freshwater systems as they provide an array of environmental goods-and-services, such as flood and erosion control, water storage and filtering, a range of food and material products, as well as opportunities for recreation. Some basins, such as the Nile, Volta and Zambezi, have large dams (>60 metres high) for water supply and power generation. New dams are currently under construction in the Niger and Orange river basins. Compared with the last few decades, the rate of construction of new dams has greatly slowed down (IUCN and others 2003).
The urban population of sub-Saharan Africa (SSA) is expanding at a rapid rate, and as a result there is a rise in demand for potable water supply. Changing population patterns and growth are discussed in Chapter 1: The Human Dimension. Groundwater can be a viable resource to meet growing demand provided the necessary protective and institutional measures are in place and enforced. Annual groundwater recharge per capita is lowest for Northern Africa: 144 m3 per capita for the Atlas Mountains and 350 m3 per capita for the North African basins; the extent of groundwater development in these parts is 49 per cent and 22 per cent of mean annual groundwater recharge respectively (IGRAC 2004). In other sub-regions, annual groundwater recharge ranges from 2 400 to 9 900 m3 per capita (IGRAC 2004).
Climate change and variability, population growth and increasing water demand, overexploitation and environmental degradation have significantly contributed to the worsening of the state of freshwater resources, leading to an increasing number of African countries where water demand outstrips available resources. Fourteen African countries experience water stress (less than 1 700 m3 per capita/year) or water scarcity (less than 1 000 m3 per capita/year; WRI and others 2000).