WATER RESOURCES OF NIGERIA

WMA 307WMA 307Dr. A.O. Idowu, Dr. G.C. Ufoegbune and Dr O.Z. OjekunleDr. A.O. Idowu, Dr. G.C. Ufoegbune and Dr O.Z. OjekunleDept of Water Res. Magt. & AgrometDept of Water Res. Magt. & AgrometUNAAB. Abeokuta. Ogun StateUNAAB. Abeokuta. Ogun StateNigeriaNigeriaoojekunle@yahoo.com

Rainfall; Pattern, spread and quantity. Daily, monthly and yearly rainfall in different regions of the country.

Climate and Water Resources of Nigeria: Factors affecting precipitation in Nigeria.

Variation of Precipitation in Nigeria (a) Seasonal Distribution – Critical months in terms of rainfall

distribution in Nigeria. Infuence of the Maritime winds and Continental winds.

(b) Variations in Total Annual Rainfall: Regions of high and low rainfalls, latitudinal distribution, regions of anomalies and causes of the anomalies.

(c) Variations in rainfall regimes: What are rainfall regimes and causes.

Divides of the country into different regimes, anomalies and causes.

Evapotranpiration in Nigeria

Division of Nigeria into different evapotranspiration zones

Agencies Agencies: Federal Ministries of

Agriculture and Water Resources. Water Corporations, Department of Waterways and Navigation, River Basin Development Authorities, Research Institutes, Universities.

Agencies Examined

Examination of the agencies of water development: The Federal Government – The ministry of Water Resources. Sectors of the

Minstry- Hydrology and Hydrogeology Division, Dams and Reservoir operations and Waste water and environmental sanitation.

Parastatals in form of River basin development authorities, functions and locations all around the country.

Other agencies- PTF, DEFFRI, OMPADEC, etc. State gvernments as agents of water developments- water corporations. Local governments as agents of water developments Department of Waterways. Research Institutes and Universities Non-Governmental Agencies-

 

Rivers in Nigeria;

Main rivers and their flows, average flow, maximum and minimum flow, annual yields. Rivers Niger, Benue, Ogun, Kaduna, Sokoto, Rima, Hadejia, Jamaire, Gurara, etc.

Lakes and reservoirs:

Natural and artificial lakes. Reservoirs above dam – Kainji, Jebba, Tiga dams and reservoirs etc. Reservoirs behind small and medium earth dams in different States in Nigeria.

 

Niger River

The Niger River is the principal river of western Africa, extending about 4,180 km 4,180 km (2,600 mi).(2,600 mi). Its drainage basin is 2,117,700 km2 (817,600 sq mi) in area. Its source is in the Guinea Highlands in southeastern Guinea. It runs in a crescent through Mali, Niger, on the border with Benin and then through Nigeria, discharging through a massive delta, known as the Niger Delta of the Oil Rivers, into the Gulf of Guinea in the Atlantic Ocean. The Niger is the third-longest river in Africa, exceeded only by the Nile and the Congo River (also known as the Zaïre River). Its main tributary is the Benue River.

The Niger River basinThe Niger River basin, located in western Africa, covers 7.5% of the continent and spreads over ten countries (Map 1 and Table 1).

Country Total area of the country (km2

)

Area of the country within the basin (km2)

As % of total area of basin (%)

As % of total area of country (%)

Average annual rainfall in the basin area

(mm)

min. max. mean

Guinea 245857 96880 4.3 39.4 1240 2180 1635

Côte d'Ivoire 322462 23770 1.0 7.4 1316 1615 1466

Mali 1240190 578850 25.5 46.7 45 1500 440

Burkina Faso 274000 76621 3.4 28.0 370 1280 655

Algeria 2381740 193449 8.5 8.1 0 140 20

Benin 112620 46384 2.0 41.2 735 1255 1055

Niger 1267000 564211 24.8 44.5 0 880 280

Chad 284000 20339 0.9 1.6 865 1195 975

Cameroon 440 89249 3.9 18.8 830 2365 1330

Nigeria 770 584193 25.7 63.2 535 2845 1185

For Niger basin 2273946 100.0 0 2845 690

The Quantity Entering Nigeria

The area of the Niger River basin in Guinea is only 4% of the total area of the basin, but the sources of the Niger River are located in this country. The quantity of water entering Mali from Guinea (40 km3/yr) is greater than the quantity of water entering Nigeria from Niger (36 km3/yr),

The most important areas of the Niger basin are located in Mali, Niger and Nigeria (25 % in each of these three

countries).

Rivers and discharges

The Niger River, with a total length of about 4100 km, is the third-longest river in Africa, after the Nile and the Congo/Zaire Rivers, and the longest and largest river in West Africa.

Subdivided into Four The upper Niger River system The inner delta The middle Niger River system The lower Niger River system

The lower Niger River system

Leaving the border between Niger and Benin the river enters Nigeria, where it is joined by numerous tributaries. The most important tributary of the Niger is the Benue which merges with the river at Lokoja in Nigeria. The quantity of water entering Nigeria was estimated at 25 km3/year before the 1980s and at 13.5 km3/year during the 1980s.

In Nigeria itself the Benue is joined by several tributaries, of which the ones at the left side originate mainly in Cameroon.

The Benue reaches its flood level in September. It begins to fall in October and falls rapidly in November,

Reaches its lowest level in March and April. From the confluence with the Benue, the Niger heads

southwards and empties in the Gulf of Guinea through a network of outlets that constitute its maritime delta.

Average annual discharges of the Niger River and its main tributaries in Nigeria over different periods Before and After 1980

River Measuring station

Average flow before 1980 (km3/year)

Average flow in the 1980s (km3/year)

Difference (%)

Kaduna Wuya 16.5 14.8 -10

Benue Yola 25.0 13.5 -46

Benue Makurdi 94.0 74.9 -20

Benue Umaisha 108.0 76.7 -29

Niger Jebba 40.7 24.3 -40

Niger Baro 61.4 43.3 -29

Niger Lokoja 171.5 137.9 -20

Niger Shintaku 173.8 139.0 -20

Niger Idah 177.0 147.3 -17

The irrigation sector in Nigeria can be divided into three categories

• public irrigation schemes, which are government-executed schemes;• farmer-owned and operated irrigation projects (improved fadamas);• residual fadamas or floodplains.

Problems of Irrigation

Estimating irrigation potential is rather difficult, despite the considerable data available on surface water resources, because of the potential of large areas to be irrigated either by surface water or shallow fadama aquifers, two sources that are hydraulically connected. Table 4 presents irrigation potential as identified in the national water resources master plan (NWRMP)

Table 4: Niger River basin: irrigation potential, water requirements, water availability and areas under irrigation

Country with an area within

the Niger basin

Irrigation potential

Gross irrigation

water requireme

nt

Actual flows Flows after deduction for irrigation

and losses

Area already under irrigation (ha)

per ha total inflow

outflow

inflow outflow

(ha) (m3/ha. year)

(km3

/yr)

(km3/yr)

(km3

/yr)

(km3/yr)

(km3/yr)

Guinea 185000 23500 4.35 0.00 40.40

0.00 36.05 6000

Cote d'Ivoire 50000 23500 1.18 0.00 5.00 0.00 3.83 0

Mali 556000 40000 22.24

45.40 29.20

39.88 6.96 187500

Burkina Faso 5000 7000 0.04 0.00 1.40 0.00 1.37 850

Benin 100000 18500 1.85 0.00 3.10 0.00 1.25 740

Niger 222000 37000 8.21 33.70 36.30

9.58 3.96 67520

Cameroon 20000 18500 0.37 0.00 13.50

0.00 13.13 2000

Nigeria 1678510 10000 16.79

49.80 177.00

17.09 rest to sea 670000

Sum of countries

2816510 55.02

924610

Total for Niger basin

<= 2816510

Rivers to the Country’s Coast:

The river catchment basins in the coastal zone consist of the western Nigeria catchment basin, the Niger Benue catchment basin, and the south-eastern catchment basin.

The major rivers in the western Nigerian catchment basin consist of Ogun, Owena, Osun and Shasha which are sourced from the Yoruba highlands and drain the

landmass in the south western part of Nigeria. These rivers empty into the Lagos lagoon.

Niger Benue catchment

The Niger Benue catchment basin is dominated by the Niger and Benue rivers. The Niger River flowing over coarse, crystalline, Cretaceous

and Cenozoic base complex enter the country in the west, and has a total length of 4 123 km - making it the eleventh

longest river in the world.

Other Tributaries

At Lokoja, the Niger River is joined by the River Benue before continuing its course due south into the Gulf of Guinea. Other important tributaries of the Niger include

Rivers Sokoto, Zanfara and Kaduna. Some 233 km below the Lokoja at Aboh, the Niger River starts to break up

into tributaries to form a delta. The Niger River drains a total area of 621,351 km2. NEDECO, (1961) estimated the annual discharge of freshwater to the delta to be 200 x 109 cubic metres, while total annual discharge has also been estimated to be about 300 x 109 cubic metres.

The South Eastern Catchment

The south eastern river catchment basin is drained by Imo River, Calabar and several other smaller rivers which take their sources from the

eastern highland south of the Benue River. These rivers empty into the ocean through estuaries.

Lake and Dams in Nigeria

The Challawa Gorge Dam is in Kano State in the Northeast of Nigeria, about 90 km southwest of Kano city. It is a major reservoir on the Challawa River, a tributary of the Kano River, which is the main tributary of the Hadejia River.

The dam is owned and operated by the Hadejia-Jama’are River Basin Development Authority, a Federal agency.

It is 42 m high and 7.8 km in length. The dam has a full storage capacity of 904,000,000 m3. The direct catchment area is 3857 km2.

Usefulness and Issues (Challawa Gorge Dam)

Cont Hydro power potential:

3. Issues: Not stabilized Siltation. Disruption of the natural balance along the river.

Kafin Zaki Dam The Kafin Zaki Dam is a controversial project to build a

reservoir on the Jama'are River (also called the Bunga River in its upper reaches) in Bauchi State in the Northeast of Nigeria.

Proposed dam and reservoir: The proposed dam would be of zoned earthfill construction and would be 11 kilometres-long. It would be designed with the

potential to install a hydroelectric plant. As reservoir Second largest in Nigeria after the Kainji Dam. For irrigation Potential for sugarcane production Provide over one million jobs in industries related to agriculture.

Kafin Zaki Dam (Cont)

Controversy: Impact downstream flow. prevent the seasonal floods that their farmers depend upon for farming, Cause drop in water Environmentalists are also concerned about the impact on downstream

wetlands.

Kainji Dam

Kainji Dam: Reservoir on the Niger River, on the border between Niger and Kebbi states, in western Nigeria Kainji Dam is a dam across the Niger River in western Nigeria

and covers an area of 1,300 square km; it is used extensively for fishing and irrigation. The lake completely submerged Foge Island in the Niger River, the town of Bussa,

and other riverine settlements; part of the old town of Yelwa (the seat of Yauri emirate) was also permanently flooded. About 50,000 people—mostly Reshe (Gungunci, Gungawa), Busa (Busawa, Bussangi), Kamberi, Nupe, Lopawa, and Laro—were displaced.

Construction of the dam began in 1964 and was completed in 1968. The total cost was estimated at $209 million, with one-quarter of this amount used to resettle people displaced by the

construction of the dam and its reservoir, Kainji Lake. The dam is one of the longest dams in the world

Kainji Dam (Cont)

Dimensions: Kainji Dam extends for about 10 km, including its saddle dam, which closes off a tributary valley.

Most of the structure is made from earth, but the center section, housing the hydroelectric turbines, was built from concrete. This

section is 65 m (215 ft) high. Capacity: The dam was designed to have a generating capacity of

960 Megawatts; however, only 8 of its 12 turbines have been installed, reducing the

capacity to 760 Megawatts. The dam generates electricity for all the large cities in Nigeria. Some of the electricity is sold to the neighboring country of Niger.

In addition, occasional droughts have made the Niger's water flow unpredictable, diminishing the dam's electrical output.

The dam has a single-lock chamber capable of lifting barges 49 m (160 ft).

Lake Kainji: Kainji Lake measures about 135 km (about 84 mi) long and about 30 km (about 19 mi) at its widest point,

Tiga Dam

Tiga Dam: Catchment area of the Yobe River, The Tiga Dam is in Kano State in the Northeast of Nigeria, constructed in 1971-1974. It is a major reservoir on the Kano River, the main tributary of the Hadejia River. Water from the dam supplies the Kano River Irrigation Project as well as Kano City. Several studies have shown that the dam has delivered negative economic value when its effect on downstream communities was taken into account.

The Hadejia-Nguru wetlands further downstream have considerable economic and ecological importance. They are home to about one million people living by wet-season rice farming, agriculture at other seasons, fishing and cattle grazing by Fulani people. The dam has damaged the cycle, reducing fish catches and harvests of other wetland products.

IMPACTS OF DAMS

Ecological impact of dams Emission of Greenhouse Gases (GHG) Alteration of Flow Regime: Biodiversity Loss: Social Impact: Gender-Related Impacts: Impact of Cultural Heritage Health Related Impacts:

DAM DISASTERS IN NIGERIA

Shiroro Dam: Over 26 villages in Kede, Lakpma and Shiroro Local Government in Niger State were flooded by the waters from Rivers Niger and Kaduna in 2003. The flood displaced about 10,000 persons in Ketsho in Kede Local Government who were said to have moved to Kwara State, while other 13,500 person in Lakpam and Shiroro were rendered homeless.

Obudu Dam: The Obudu Dam spillway was damaged by storm in July 2003 which resulted in fatal disaster that claimed over 200 houses, several farmlands, settlements and business concerns.

Igabi Dam: Property worth about N500 million ($3.9m) were destroyed while thousands of people were rendered homeless in Kaduna State when River Kaduna overflowed its banks and submerged several streets and housing estates. The flood was caused by the collapse of Igabi Dam.

DAM USES IN NIGERIA (Cont)

Dam Uses MP = Multipurpose use WS = Water supply RC = Recreation IR = Irrigation NA = Not available

Groundwater: Exploitation Through Tube wells and Boreholes

The availability of ground water for the development of any State or Community in the country depends on the hydrogeological characteristics of the underlying ground water province in the area. It is therefore necessary to study, identify and evaluate the water resources of the hydrogeological province in any area and develop an exploitation strategy that best suites the province.

Examples of hydrogeological characteristics Coastal Alluvium is restricted to the Coastal States like, Cross River, Akwa-Ibom Rivers, Bayelsa, Delta, Edo, Ondo, Ogun and Lagos States.

The River Course Alluvium traverses the whole country following the various rivers systems draining the country.

While the Coastal Sedimentary areas underlie the southeast States of Imo, Anambra Abia, Enugu, parts of Delta,

While the Crystalline Area or Basement, occupies most of the Sahelian northern States Like, Kano, Bauchi, Kwara, Oyo, Niger, Kaduna Plateau, Adamawa, Taraba etc.,

the Basement Complex hydrogeological Province, occupies nearly half and most of the Central area of the Country..

Notes

It is therefore apparent that despite the obvious poor hydrogeological properties of the Crystalline or Basement Complex province, the area cannot be ignored in the Water Resources Development of the Country.

Similarly, despite, the apparent good ground water prospects of the Sedimentary regions, problems like, Saline intrusion in the Coastal areas, depth of occurrence and the predominance of impermeable shales and clays in the sedimentary sequence present obstacles in the ground water development of those areas of the country

Tube wells and Boreholes

Depth for depth on any given site, hand-dug wells may yield more water than tubewells,

Xteristies of Tubewell 100 or 150 mm diameter are usually quicker and cheaper to sink, need no dewatering during sinking, require less lining material, are safer in construction and use, and involve less maintenance. From a hygienic point of view, the fact that a pump is needed

to lift water from a tubewell is an asset, not a liability.

Features of Tubewell and Technological Equipment

This section describes some features of tubewells which have handpumps, and two methods of sinking them in generally soft ground

Equipment using only man-powered low-technology equipment, namely,

hand auguring using a Vonder rig, and sludging.

The casing Use PVC, "down-the-hole", which can be lifted out for maintenance or

repair.

Seepage down the tubewell bore is prevented by the sanitary seal. Seepage from the ground above the aquifer is excluded by the lengths of plain casing. Water to be pumped is admitted through slots in the lower lengths of casing.

Casing to support the external surfaces of the borehole against collapse may be needed, either temporarily or permanently, but is not shown.

Water abstracted from aquifers in relatively soft ground usually contains sand or silt particles, which are liable to cause rapid wear to pump valves and cylinders (and dissatisfaction among consumers).

Methods of preventing these particles from reaching the pump

Screening

Sand/gravel packing.

Developing the well

Over-pumping (that is, pumping at above the design-rate) before the well enters service can improve the efficiency of the packing by drawing further fine particles into it. Where the surrounding ground has many fine particles, the flow of water can be accelerated by back-flushing at a higher rate. 

This over-pumping and back-flushing is known as developing the tubewell.

Sinking tubewells

At least two experienced operators are required; communities will usually supply unskilled labour. Samples of the excavated material should be taken at regular intervals of depth (and also if the strata changes) and a borehole record should be kept.

Particular attention is needed to maintain verticality. A "down-the-hole" pump which has been installed out of the vertical may be hard to operate and subject to excessive wear.

Auguring

Auguring cuts earth away by the rotation of a cylindrical tool with one or more cutting edges. The excavated earth feeds upwards inside the tool body, which needs lifting to the surface for emptying at intervals.

This requires the whole auguring (drilling) train to be uncoupled and lifted; the weight involved can be considerable, and puts a limit to the depth of hand-operated auguring.

Auguring using the Vonder Rig

The Vonder Rig, can sink a tubewell hole up to 170mm in diameter and about 115m deep in about two days in ground which is predominantly soft. The next drawing shows its salient parts, all of which are made of mild steel and can be carried by hand between sites.

The crossbar is friction-bolted to a stem, at a height suitable for pushing round by hand. Helpers can sit on it if auguring needs extra weight (or even if it doesn't). Additional stem sections are added as auguring proceeds.

Several shapes and sizes of auger-bit are provided, including a "hole-saw"; this is intended to tackle soft rock, but has rarely been successful. Thin layers of rock have been penetrated, however, by an improvised arrangement including a slow-speed diesel drive to the drilling train.

Sludging Sludging is an effective method of sinking tubewells. Sludging is a cheap but effective method of sinking small-diameter tubewells to a

great depth in the water-logged silts and fine sands which underlie some flat river plains and deltas, notably those in the Indian subcontinent

Tubewells 25mm and upwards in diameter (the larger ones are able to accommodate a "down-the-hole" pump) are sunk to depths of 60m or more. A boring pipe, usually a galvanised mild steel tube fitted with a case-hardened open socket at its base, moves vertically under the action of a bamboo lever pivoted on an H-frame.

For the duration of each upstroke, another man seals the open top of the pipe with his hand, creating a partial vacuum inside it, so that the water within the pipe rises with it. He removes his hand for the downstroke, during which the pipe drops faster than the water inside it. As this hand-on / hand-off cycle repeats, water starts to gush from the top of the pipe and the whole assembly begins to work as an elementary force pump.

Additional lengths of boring pipe are attached successively until the required depth is reached. The whole pipe is then withdrawn and replaced by PVC rising main (for a suction pump) or PVC casing (for "down-the-hole" pumps).

Other methods of drilling

WaterAid prefers the simplest methods of drilling, particularly those which can be operated by villagers themselves. However, there are several other, more complicated, techniques which can be used and the next few diagrams illustrate the following methods:

Percussion drilling Rotary percussion drilling Rotary drilling with flush Jetting

Tidal and Saline water in Coastal areas

Coastal Geomorphology and Habitat: The Nigerian coastal and marine area consists of a narrow coastal strip of land bordered by the Gulf of Guinea of the Central Eastern Atlantic. The coastal areas stretch inland for a distance of about 15 km in Lagos to about 150 km in the Niger Delta and about 25 km east of the Niger Delta.

The Nigerian coastal area is divided into four main geomorphic zones (figure 1) namely:

Barrier Lagoon Coast Mahin Mud Coast Niger Delta Strand Coastline

Xteristics of Niger Delta

The Niger delta spreads over a number of ecological zones; sandy coastal ridge barriers, brackish or saline mangroves, freshwater permanent and seasonal swamp and lowland forests.

The mangroves and wetlands along the major estuaries between Benin river in the west and Cross River in the east have a total brackish area of 2 520.79 km2

Coastal Currents and Tides

The Nigerian coast and marine areas are influenced by tides, waves, long shore currents, and ocean currents.

Tides along the entire Nigerian coast are semi diurnal with two

tides arrive in a south westerly direction. Tidal range varies from 1m at Lagos and increases progressively eastwards to about 3 m at Calabar. Intense tidal activities are more destructive along the Mahin coast during spring tides, during which tidal range reaches 1.5m.

Saline

Water is classified as "saline" when it becomes a risk for growth and yield of crops. Saline water has a relatively high concentration of dissolved salts (cations and anions). Salt is not just "salt" as we know it - sodium chloride (NaCl) - but can be dissolved calcium (Ca2+), magnesium (Mg2+), sulfate (SO4

2-), bicarbonate (HCO3-), Boron (B), and other compounds.

Water can be both saline and sodic, or saline-sodic. If water has an EC greater than 4 (2 for horticulture) and a Sodium Adsorption Ration (SAR) greater than 12, it is considered saline-sodic

The concentration is usually expressed in parts per million (ppm) of salt.

If water has a concentration of 10,000 ppm of dissolved salts, then one percent (10,000 divided by 1,000,000) of the weight of the water comes from dissolved salts.

Classification of Salinity

Slightly saline water contains around 1,000 to 3,000 ppm.

Moderately saline water contains roughly 3,000 to 10,000 ppm.

Highly saline water has around 10,000 to 35,000 ppm of salt.

Seawater has a salinity of roughly 35,000 ppm, equivalent to 35 g/L.

Salinity in Different Water Bodies

Water salinity based on dissolved salts in parts per thousand (ppt)

Fresh water Brackish water Saline water Brine

< 0.5 0.5 – 30 30 – 50 > 50

Effects of Salinity Saline water reduces plant growth to varying degrees, with grass and

grain crops generally showing less sensitivity and field crops being most sensitive. Aside from biomass reduction, salinity can have additional effects on plants. For example, in a study by Bauder et al., both inoculated and non-inoculated alfalfa were grown with irrigation waters of progressively higher salinity levels

Correction of Salinity There are no amendments, chemicals, or additives available

commercially that can be added to saline water to make the salt go away. Dilution with a non-saline water or salt precipitation with an evaporation process which leaves the salt behind and traps the evaporated water can be used. Dilution of saline irrigation water is only possible if there is a source of non-saline water with which to dilute the saline water