GEO-6 Regional Assessment for Africa


2.3.4


Transboundary water resources


There are 63 transboundary river basins in Africa, covering 64 per cent of the continent’s land area and containing 93 per cent of its total surface water resource (UNEP 2010). Water supplies for big cities and irrigation are drawn from major dams erected on both local and international rivers where lake and river basin commissions are responsible for the management of these shared resources. Riparian countries often have varying requirements. On the Nile, for example, Uganda is highly dependent on the river for hydropower, while in Egypt much of the water is used for agriculture and domestic purposes.


Africa also has transboundary aquifers, found mainly in zones of high water demand. Some transboundary aquifers, such as the Nubian Sandstone Aquifer System, contain non-renewable water that was stored a long time ago. The


Figure 2.3.9: Transboundary aquifers and international river and lake basins in Africa


¯


Atlas Mountains Transboundary aquifers


Tindouf Aquifer


Taoudeni Basin


Senegalo-Mauretanian Basin


l'Air


Crystalline Aquifer


Liptako-Gourma Aquifer


Tano Basin


Northwest


Sahara Aquifer System (NWSAS)


Mourzouk-Djado Basin


Tin-Séririne Basin


Irhazer-Iullemeden Basin


Keita Basin


Lake Chad Basin


Eastern Mediterranean


Nubian Sandstone Aquifer


System (NSAS) Disa Gedaref


Baggara Basin Sudd Basin


Mount Elgon


Mgahinga Congo


Intra-cratonic Basin


Cuvelai


and Etosha Basin


Northern Kalahari /


South-east Kalahari /


Karoo Basin


Transboundary aquifers and international river/lake basins Aquifers Transboundary river basins


Source: Oregon State University (OSU), 2007/International Groundwater Resources Assessment Centre (IGRAC), 2009 Source: Altchenko and Villholth 2013 66


Nata Karoo Sub-basin


Karoo Basin


Medium Zambezi Aquifer


Limpopo Basin


Karoo


Sedimentary Aquifer


Mangrove forests inhabit many of the saline and brackish coastal and marine areas of the continent’s coastline, in East Africa stretching from the coastal cities of Kismayu in Somalia to Maputo in Mozambique, on the West African coastline


Aquifer Coastal


Sedimentary Basin 1


Coastal


Sedimentary Basin 3


African


Rift Valley Aquifer


Merti


Shabelle Jubba


Aquifer


Constructed wetlands are designed for the treatment of wastewater from settlements and mining, while natural wetlands are


under immense


water demand that results from population increase and stress induced by climate change may increase aquifer uses and rates of depletion, thus increasing the complexity and challenges of aquifer management.


Aquifers in arid and semi-arid regions such as North, Southern and West Africa are likely to be affected by high temperatures, decreased precipitation and increasing water scarcity, as well as greater water use. An estimated 75 per cent of Africa’s population is dependent on groundwater resources (Altchenko and Villholth 2013) (Figure 2.3.9).


2.3.5 Wetlands A wide range of wetland types is found in Africa, including natural


and constructed freshwater marshes, river


floodplains, swamps and peat lands, in addition to those containing a mixture of salt and freshwater such as estuaries and coastal lagoons (UNEP 2010). Wetlands constitute 1 per cent of Africa’s total surface area, with the largest concentration of natural wetlands occurring in the Nile, Niger, Congo and Zambezi River Basins; Lake Chad and the wetlands of the inner Niger Delta in Mali; the East African Rift �alley lakes; the Sudd in Southern Sudan and Ethiopia; and the Okavango Delta in Botswana (Figure 2.3.10).


pressure from human


activities, the most important being wastewater discharge from agriculture, settlements and industry (Abiye 2015). In South Africa, for example, wetlands are in high demand for the treatment of mine-water pollution in the gold-mining areas of the Witwatersrand. Small constructed wetlands are often used to treat wastewater, enabling biological oxygen demand to be reduced by 60 per cent and microbial load by 100 per cent (Abiye 2015).

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