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

abstracted and flow regulated. Irrigation requireslarge quantities of water and. there are, at present,more than 12.4 million hectares of irrigatedlands in Africa, which require 140 km 3 /year offreshwater. Much of this water is diverted fromrivers, lakes and reservoirs and delivered to thefields by canals (Shiklomanov, 2002). The largestirrigated lands are in Egypt (more than 3.3 millionhectares), the Sudan (1.9 million hectares),South Africa (1.3 million hectares), Morocco(1.2 million hectares) and Madagascar (1.1 millionhectares). Irrigation development is intensiveon the continent and has increased threefoldduring the last 30 years. There are sufficient reasonsto assume that irrigation development willremain intensive in the future. The reasons arethe rapid population growth, the ever-changingclimate conditions, and the fact that increasedagricultural production for food security cannotbe achieved without irrigation in most Africancountries. (Shiklomanov, 2002). Using Moroccoas an example, it can be seen from figure 6.1 thatthe extension of irrigated agriculture in Moroccosteadily increased and more than doubled from1968 to 2000 (National AWDR Report, 2005).As in other dry regions, agriculture is the largestuser of water in Africa, accounting for 88 per centof total water use (WRI, UNEP, UNDP and WB1998). However, with only 6 per cent of croplandunder irrigation, the potential to increase foodproduction through irrigation is considerableand, therefore, demand for water for irrigationwill continue to grow in Africa. About 40-60 percent of the region’s irrigation water is currentlylost through seepage and evaporation, adding tothe other serious environmental problems of soilsalinization and waterlogging, although waterlost through seepage and evaporation may endup in aquifers where it can be pumped to irrigatenearby fields.air-borne ones, are considered as major factorsthat cause and worsen tuberculosis, bronchitis,heart diseases, cancers and asthma. Tuberculosis,the single largest infectious killer of adults,was responsible for three million deaths in 1996,95 per cent of which occurred in the developingworld (WHO 1997). Exposure to pesticides,fertilizers and heavy metals poses health risksthrough soil, water, air and food contamination.Global pesticide use has resulted in 3.5-5 millionacute pesticide poisonings per year (ibid. 1990).Surface Water Ecosystems in AfricaAfrica is a continent of contrasting landscapes.About half of its territory is made up of desertsand semi-deserts, with the Sahara Desert aloneoccupying an area of about 8 million sq. km.(Nana-Sinkam, 1995). The central part of thecontinent, the Congo River Basin, is occupied bysubtropical rain forests and the Congo River isthe most full-flowing river in the Eastern Hemisphere.On the whole, Africa’s runoff resourceswhich account for its renewable freshwatersources are approximately 4050 cu. km/year. Thatis equal to 9.5 per cent of the total world riverrunoff. According to specific indices (per sq. kmand per capita) Africa is one of the continentswith the least river water availability, relating toAustralia on aerial water availability and to Asiaon river runoff per capita (Shiklomanov, 2002).The water availability of Africa is 2.4 times lowerthan that of the world land area (without Antarctica).Some characteristics of major naturallakes in Africa are shown in table 6.1.Protecting Ecosystems in AfricaIn many developing regions, traditional environmentalhealth problems are now exacerbated byemerging problems of pollution from industryand agriculture. Chemical agents, particularly127