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GEOGRAPHY, POPULATION AND WATER RESOURCES
Nigeria is located in the tropical zone of West Africa, with an area of 923 770 km² The total cultivable area is estimated at 61 million ha, which is 66% of the total area. The net cultivated area is about 22.6 million ha, which is 37% of the cultivable area and 24% of the total area. Wetland and bare-land represent 2.6% and 8.5% of the country's area, respectively.
Total population is about 108 million (1994), of which 57% is urban. The average population density is 117 inhabitants/km². The annual demographic growth rate is currently estimated at 3.1 %.
Basic statistics and population
|Area of the country||1994||92 377 000 ha|
|Cultivable land||1989||61 000 000 ha|
|Cultivated land||1989||22 600 000 ha|
|Total population||1994||108 467 000 inhab|
|Population density||1994||117 inhab./km²|
|Rural population||1990||65 %|
|Water supply coverage|
|Urban population||1993||50 %|
|Rural population||1993||9 %|
Agriculture employs about 66 % of the labour force. In 1989 it contributed about 29% of GNP.
Climate and water resources
The climate is semi-arid in the north, and humid in the south. Except for the coastal zone, where it rains all year round, rainfall is seasonal with distinct wet and dry seasons. Rainfall is concentrated in the period June-September, with the south receiving 50-60% of its rainfall and the north receiving 90%. Rainfall varies from under 500 mm/year in the northeast to over 3 000 mm/year on the coast.
Surface water flowing from Nigeria to the sea is estimated around 263 km3/year. There are four main river systems: the Niger-Benue, the Chad basin area, the Southwestern littoral and the Southeastern littoral, with trans-border flows from Cameroon. Nigeria receives an estimated 30 km³ from Niger (although in the 1980s the average flow of the Niger at the border was about 18 km³ and 29 km³ from Cameroon in the Benue and tributaries. Ground-water resources are estimated at around 87 km3/year, of which a great part (about 80 km³ constitutes the base flow of major rivers.
|Average precipitation||1 177||mm/yr|
|Internal renewable water resources- total||221.0||km³/yr|
|Internal renewable water resources - per caput||1994||2 037||m³/yr|
|Global renewable water resources||280.0||km³/yr|
|Total dam capacity||1993||30.3||km³|
|De-salinated water||1990||3||10 6 m³/yr|
|- Agricultural||1987||1 960||10 6 m³/yr|
|- Domestic||1987||1 125||10 6 m³/yr|
|- Industrial||1987||545||10 6 m³/yr|
|Total||3 630||10 6 m³/yr|
|as a % of internal renewable water resources||1.6||%|
|Other withdrawal||-||10 6 m³/yr|
|Produced||-||10 6 m³/yr|
|Treated||-||10 6 m³/yr|
|Re-used treated wastewater||-||10 6 m³/yr|
Irrigation and drainage
|Irrigation potential||1993||3 137 000||ha|
|1. Full or partial control Irrigation: equipped area||1991||219 621||ha|
|- surface irrigation||-||ha|
|- sprinkler irrigation||-||ha|
|% of area irrigated from groundwater||-||%|
|% of area irrigated from surface water||-||%|
|% of equipped area actually irrigated||1991||74||%|
|2. Spate irrigation area||-||ha|
|3. Equipped wetland and inland valley bottoms||1991||13 200||ha|
|4. Other cultivated wetland and inland valley bottoms||-||ha|
|5. Flood recession cropping area||1991||723 714||ha|
|Total water managed area (1 +2+3+4+5)||1991||956 535||ha|
|- as % of cultivated area||1991||4.2||%|
|- increase over last 10 years||-||%|
|- power irrigated area as % of water managed area||1991||13.4||%|
|Full or partial control schemes:||Criteria|
|Large schemes||> - ha||-||ha|
|Small schemes||< - ha||-||ha|
|Total number of households in irrigation|
|Total irrigated grain production||1989||1 852 200||t|
|as a % of total grain production||1989||14.2||%|
|Harvested crops under irrigation||1989||950 000||ha|
|- rice||1989||714 000||ha|
|- vegetables||1989||137 000||ha|
|- wheat||1989||50 000||ha|
|- potatoes||1989||26 000||ha|
|- other||1989||23 000||ha|
|Drainage - Environment:|
|as a % of cultivated area||-||%|
|Area salinized by irrigation||-||ha|
Total active reservoir capacity is 30.3 km³ (1993). The bulk of dam construction took place in the late 1970s and in the 1980s. A total of 60 large dams and 100 small dams have been built so far. Water allocation from reservoirs is shared as follows: 10.9 km³ (36 %) for irrigation, 0.8 km³ (3%) for water supply, and 18.6 km³ (61 %) for hydropower.
Agricultural, domestic and industrial water withdrawal was estimated at 3.6 km³ in 1987 (Figure 1).
Under natural hydrological conditions, the rivers deposit rich sediments in the fadama (flood plains) during flood. These areas mitigate the downstream effect of flooding and help the recharge of the shallow aquifers; in addition their natural vegetation supports large and diverse wildlife populations. Their use is subject to conflicting interests between local people, who use them for agriculture, fishing, grazing or hunting; national-level planners, who wish to intensify production through development of irrigation and river control; and conservationists, who are concerned about the environmental role of wetlands.
Irrigated crops represent about 8% of the value of the country's total agricultural crop output, and 4% of the cultivated area.
The conjunctive use of surface water and shallow fadama aquifers makes assessment of irrigation potential particularly difficult. According to the National Water Resources Master Plan Study, total irrigation potential would be about 3.14 million ha: 1.10 million ha for public irrigation projects, and 2.04 million ha for formal fadama irrigation projects. Other sources estimate total irrigation potential to be about 2 to 2.5 million ha.
Estimates of irrigated land area and of irrigated crops also vary greatly from one source to the other. The Total water managed area is estimated to be about 950 000 ha, but it is not clear if this includes double cropping.
Irrigation systems can be divided into three main categories, as shown in Table 4.
Public irrigation projects are schemes under government control (formal irrigation). It is estimated that only 52% of the public irrigation scheme area is actually irrigated (Figure 2). Farmer-owned and -operated irrigation projects (informal irrigation) receive assistance from government (subsidies and training). About 76% of the total water managed areas are residual fadamas, where no government aid is supplied (Figure 3). The part of the equipped area actually irrigated by pumping (from rivers or groundwater) is 121 181 ha or 13% of the Total water managed area (Figure 4). Sprinkler irrigation is practiced on 3 570 ha (Figure 5).
FIGURE 1: Water withdrawal (total: 3.63 km' in 1987)
|Formal irrigation (Public irrigation projects)||Full or partial control||equipped||118 621||119 350|
|actually irrigated||62 086||69 000|
|Informal irrigation (Farmer- owned and -operated irrigation projects||Full or partial control||lift or shallow tubewell||101 000||161 700|
|Equipped wetland||flood control (improved fadama)||13 200||18 500|
|Residual fadama||Flood plains||723 714||724 000|
Source: FAO/lnvestment Centre (1992), and Japanese International Cooperation Agency (1993)
The most important irrigated crop is rice, which occupies about 75% of the Total water managed area (Figure 6).
Average cost for irrigation development is estimated at $US 15 000/ha (1993). Annual operation and maintenance costs varied in 1990 between $US 50/ha for gravity systems and $US 290/ha for pumping systems, and up to $US 800/ha for sprinkler irrigation systems.
FIGURE 2: Public schemes: area equipped, divided into area actually irrigated and area not irrigated (1993)
FIGURE 3: Distribution of water managed areas (1991)
FIGURE 4: Origin of irrigation water, part of full or partial control equipped area actually irrigated (1991)
FIGURE 5: Irrigation techniques, part of full or partial control equipped area actually irrigated (1991)
Nigeria is a member of two regional authorities dealing with water resources management: the Niger Basin Authority and the Lake Chad Basin Commission.
The highest national water resources policy formulating body is the National Council for Water Resources, chaired by the Federal Ministry of Water Resources. It is organized in eight Departments of Irrigation and Drainage, and promotes the development of irrigated agriculture through River Basin Development Authorities. The Federal
Ministry of Agriculture and Natural Resources is involved in irrigation development through the Agricultural Development Projects (ADPs). ADPs promote farmer-owned and -managed irrigation and provide extension services to farmers on public irrigation schemes, and are assisted by the Federal Agricultural Coordinating Unit. In some states, Ministries of Water Resources have been created and federal competences of the Ministry of Agriculture and Natural Resources in irrigation have been transferred to them.
TRENDS IN WATER RESOURCES MANAGEMENT
Nigeria is a country where population already exceeds the carrying capacity of its land resources when cultivated at low levels of technology. To increase productivity, the use of fertilizers and improved irrigation are viewed as key factors. Irrigation can increase land productivity by three to seven times, especially in the north.
A number of problems exist in the irrigation subsector. Large public projects are hampered by the very high cost of irrigation development, and by the inadequacy of planning and design of the command areas (lack of available water downstream, no provision for irrigation services) or of the irrigation canal system itself. This and a slow achievement to target yield, lead to poor financial returns to the small-scale farmers in large-scale irrigation projects. In small public projects, lack of training and extension is considered a major constraint to achieving the target incomes, together with unreliable supply of agricultural inputs.
Traditional, informal irrigation, suffers from the changing hydraulic regime of the flood plains (fadamas) due to the construction of dams and other structures upstream. Reservoir construction also generates social problems, principally due to their implicit displacement of populations.
Improvements in the irrigation subsector requires clearer and more appropriate policies and programmes; major involvement of adequately trained farmers; availability of fertilizer and seed of adequate quality; and an increasingly farmer-owned and -operated irrigation system
FIGURE 6: Irrigated crops (1989)
The flood plain of the Niger River is considered the greatest untapped potential for future irrigation development in Nigeria.
MAIN SOURCES OF INFORMATION
FAO. 1992. Irrigation Subsector review. Investment Centre Report No. 89/91 CJP-NIR 45 SR.
JICA [Japan International Cooperation Agency]. 1993. The study on the national water resources master plan. Federal Ministry of Agriculture, Water Resources and Rural Development.
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