Development of Water Projects: The variable regime of the rivers necessitates provision of storage capacity in order to meet the water needs for various purposes. A total of some 142 dams: 60 large ones (with height above 15m) and 82 small and medium ones have been constructed or are under construction. The distribution of all dams by hydrological areas (HAs) is: 44 in Has 1 and 2; 36 in Has 3 and 4; 38 in HAs 5, 6 and 7, and 24 in HAs 8. The large-scale dam projects are concentrated (85 per cent) in the five northern and central areas for perennial storage of wet season runoff to be released later for dry-season irrigation (Oyebande, 1981:201-225).
Lake Chad provides natural storage and supports one of the major irrigation projects, namely: South Chad Irrigation Project. However, it is a shallow lake 1.5-5m in depth, and its surface area is very sensitive to change in the level resulting from the basin's water balance (rainfall and inflows minus evaporation and seepage). Over 90 per cent of the total inflow is contributed by the Chari-Logone river system outside Nigeria. In all, some 17,000 water wells have been sunk or drilled, almost exclusively for water supply for humans and animals. About 85 per cent of the boreholes are developed in three northern hydrological areas where the large-scale dams have also been developed in response to their water problems.
Water Supply: The States, through their water supply agencies (WSA), have primary responsibility for urban water supply. The River Basin Development Authorities (RBDAs) release water from their dams to State agencies at agreed rates of charge for water supply development. A number of changes which occurred since 1985 have however, significantly shaped the policy horizon for urban and rural water supply management. The urban centres served (95 per cent) have, on the average, 62 litres per capita per day (lpcpd) while the level for rural areas served is 24 lpcpd. An average of at least 112 l/c/d is recommended for the hot climatic conditions of the nation's developing economy.
Irrigation: The estimated irrigable area in Nigeria is of the order of 500,000ha, but the actual irrigated area is only 60,000ha, made up of 53,000ha in RBDA projects, while the States account for 7,000ha. The major irrigation projects include Bakolori in Sototo State (23,000ha); Dadin Kowa in Gombe State (44,000 ha); Kano River Project (Tiga Dam, 25000 ha) and Challawa Gorge, (25,000ha) both in Kano State. About 150 new projects covering one million ha of irrigable area and including storage dams, diver dams, inter basin water transfer, and river training have been pro- posed for future implementation.
Hydro-electric Power: NEPA's power system has grown rapidly from supplying a peak demand of 576 MW in 1975 to 1,329 MW in 1981, with a total system capacity of 2,408 MW in 1982 of which hydro power component was 32 per cent. Only 1 1,448 MW was however available in 1982. The installed capacity of potential hydro development gives Namplate capability (at plant factor of 0.5) of 6,530 MW and average annual energy of 30,690 Gwh from 29 hydropower projects (Motor Columbus, el al, 1980).
Navigation: The improvement in river flow through regulation by dam and associated reservoirs such as Jebba, Shiroro, Kainji, Lagdo (Cameroun) and, eventually, Zungeru has led to real and potential long-term expansion of the inland waterways. The navigable distance on the Niger is 560km at the lowest acceptable draft (LAD) of 1.5 2.5m and present navigation season of 8-1 months with possibility of 12 months but, in each case, with reduction by one month during the d season due to upstream agricultural developme utilisation.
Nigeria is endowed with abundant water resources. The per capita share of surface water alone is of the order of 3,000m per annum. Areas which are deficient in surface water (e.g. the Sahelian zone) or whose surface water is contaminated by saline intrusion or oil pollutant (e.g. Nig Delta) are adequately compensated with ground water resources. The lower reliability of the runoff resulting from the variable regime, however, necessitates flow regulation by dams. There is need plan and design such dams on the basis of adequate hydrological data and in coordination with the upstream riparian states which control what reaches as Nigeria from the major river and lake basins such as the Niger,Benue and the Chad.