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

Table 8.13: Specific Nutrients found in the Major Plant GroupsPlant groupNutrientCerealsCarbohydrates, protein, dietary fibre, vitamin B complex, iron, calciumaRootsCarbohydrates, protein, some vitamin CLegumes, oilseeds, nutsCarbohydrates, protein, dietary fibre,a iron,a calcium,a vitamin B complexaFruits and vegetablesVitamin C, vitamin A, iron, calcium, vitamin B complex, dietary fibreSource: FAO, 1997.WATER FOR FOOD SECURITYIrrigation potential and water managedareasThe diversity of water management situationsencountered in Africa requires the choice of aclassification that would best represent the situationof irrigation in each country. The land onwhich water is used for the purpose of agriculturalproduction has been referred to as watermanaged areas. The term ‘irrigated areas’ hasbeen limited to the part of water-managed areasequipped with hydraulic structures: full or partialcontrol irrigation, equipped wetland or valleybottoms and areas equipped for spate irrigation.The difference between the two categories is thatthey comprise cultivated wetland and valley bottomswithout irrigation equipment or recessioncropping areas. Water managed areas comprise14.3 million hectares in Africa. There is a veryheterogenous geographical distribution of water-managedareas: the North has more than 40per cent of the total. Water-managed areas in nationalagriculture vary from less than 1 per centof cultivated land (Democratic Republic of theCongo, Comoros, Ghana, Togo and Uganda) to100 per cent in the most arid countries (Egyptand Djibouti, where agriculture is impossiblewithout irrigation). This distribution of watermanagedareas clearly shows the relationshipbetween climate and the role of irrigation in agriculture(FAO, 1995).In Equatorial Africa, where precipitation is greatest,rain-fed agriculture is dominant. Irrigation isused for winter crops and rice cultivation, or inwetlands and inland valleys, and to secure highvalue crops. In Madagascar, rice cultivation onthe plateaus is highly developed, which explainsthe high percentage of irrigation in that countryeven though rainfall is relatively favourable. Atthe national level, the distribution of water-managedareas is very uneven. Five countries (Egypt,Madagascar, Morocco, South Africa and theSudan), which cover 19 per cent of Africa, holdmore than 60 per cent of the water-managed areas.By adding Nigeria, Algeria, Libya, Angolaand Tunisia, more than 80 per cent of the watermanagedarea is controlled by 10 countries. Incontrast, 28 countries, covering more than 30 percent of Africa, share a mere 5 per cent of watermanagedlands (Fig. 8.7).Irrigation potential in AfricaAs a result of its close relationship with waterresources, irrigation potential is also unevenlydistributed between the regions. It is significantto observe that this value is much less known andstudied in countries benefiting from importantwater resources than in more arid countries. Itshould also be noted that the important transfersof water resources from humid to arid regionsallow these latter to benefit from an irrigationpotential much larger than their internal waterresources would permit, notably Egypt. This isthe case of the regions traversed by the RiversSenegal, Chari and Niger in West Africa; Nile,Juba and Shebele in Eastern Africa; and Limpopo,Orange and Zambezi in Southern Africa,to name some of the most important. The existenceof inter-regional rivers and water transfershampers the computation of irrigation potentialon a regional basis, since this may lead to double205