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Groundwater in Nigeria is widely used for domestic, agricultural, and industrial supplies. The
Joint Monitoring Programme for Water Supply and Sanitation The Joint Monitoring Programme (JMP) for Water Supply and Sanitation by WHO and UNICEF is the official United Nations mechanism tasked with monitoring progress towards the Sustainable Development Goal Number 6 (SDG 6) since 2016. Previously, u ...
estimate that in 2018 60% of the total population were dependent on groundwater point sources for their main drinking water source: 73% in rural areas and 45% in urban areas. The cities of Calabar and Port Harcourt are totally dependent on
groundwater Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidate ...
for their water supply. In 2013, there were around 65,000 boreholes in
Nigeria Nigeria ( ), , ig, Naìjíríyà, yo, Nàìjíríà, pcm, Naijá , ff, Naajeeriya, kcg, Naijeriya officially the Federal Republic of Nigeria, is a country in West Africa. It is situated between the Sahel to the north and the Gulf o ...
extracting an estimated 6,340,000 m3/day.JICA (2014). The project for review and update of Nigeria national water resources master plan; Vol.2.
/ref>Ministry of Water Resources (2013). National Water Resources Master Plan The majority of these (almost 45,000) were equipped with
hand pump Hand pumps are manually operated pumps; they use human power and mechanical advantage to move fluids or air from one place to another. They are widely used in every country in the world for a variety of industrial, marine, irrigation and leis ...
s and used for water supply in rural areas and small towns. Estimates of total renewable groundwater resources in Nigeria are variable. The United Nations
Food and Agriculture Organization The Food and Agriculture Organization of the United Nations (FAO)french: link=no, Organisation des Nations unies pour l'alimentation et l'agriculture; it, Organizzazione delle Nazioni Unite per l'Alimentazione e l'Agricoltura is an intern ...
(FAO) estimates that Nigeria has 87,000 Million m3/year of renewable groundwater resources. Japan International Cooperation Agency (JICA) estimate that total annual
groundwater recharge Groundwater recharge or deep drainage or deep percolation is a hydrologic process, where water moves downward from surface water to groundwater. Recharge is the primary method through which water enters an aquifer. This process usually occurs in ...
is 155,800 Million m3/year. Recharge is variable across the country and largely controlled by climate: recharge is lower in the north of the country due to higher evapotranspiration and lower rainfall.


Groundwater Environments


Geology

The geology of Nigeria includes large areas where
Precambrian The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the ...
basement A basement or cellar is one or more floors of a building that are completely or partly below the ground floor. It generally is used as a utility space for a building, where such items as the furnace, water heater, breaker panel or fuse box, ...
rocks are present at the ground surface, and other large areas where the basement rocks are overlain by younger
sedimentary rock Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...
s.Tijani M, Crane E, Upton K, Ó Dochartaigh BÉ and Bellwood-Howard I (2018). Africa Groundwater Atlas: Hydrogeology of Nigeria. British Geological Survey. Accessed 26 August 2019
/ref> In the north west, these sedimentary rocks largely consist of
Tertiary Tertiary ( ) is a widely used but obsolete term for the geologic period from 66 million to 2.6 million years ago. The period began with the demise of the non-avian dinosaurs in the Cretaceous–Paleogene extinction event, at the start ...
and
Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...
rocks of the Sokoto Basin (the south eastern part of the
Iullemmeden Basin The Iullemmeden Basin (Berber language: Iwellemmedden) is a major sub-Saharan inland basin in West Africa, extending about north to south and east to west. It covers western Niger and parts of Algeria, Mali and Nigeria. It is named after the Iu ...
), which are made up of varying amounts of
sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) ...
and
clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay par ...
, with lesser amounts of
limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...
. In the north east, Tertiary and
Quaternary The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS). It follows the Neogene Period and spans from 2.58 million years ...
rocks of the
Chad Basin The Chad Basin is the largest endorheic basin in Africa, centered on Lake Chad. It has no outlet to the sea and contains large areas of semi-arid desert and savanna. The drainage basin is roughly coterminous with the sedimentary basin of the sam ...
comprise sandstone, siltstone and shale. In the centre of Nigeria, along the course of the Benue and
Niger river The Niger River ( ; ) is the main river of West Africa, extending about . Its drainage basin is in area. Its source is in the Guinea Highlands in south-eastern Guinea near the Sierra Leone border. It runs in a crescent shape through ...
s, are Tertiary and Cretaceous sedimentary rocks of the Benue and Nupe Basins. The Benue Basin consists of continental sandstones overlain by marine and estuarine shales and limestones, while the Nupe Basin largely contains continental sandstones, siltstones, claystones and conglomerates. Along the coast, within the
Niger Delta The Niger Delta is the delta of the Niger River sitting directly on the Gulf of Guinea on the Atlantic Ocean in Nigeria. It is located within nine coastal southern Nigerian states, which include: all six states from the South South geopolitical ...
Basin, there are significant unconsolidated sediments of Tertiary to Quaternary age, comprising coarse to medium grained unconsolidated sands and gravels with thin peats, silts, clays and shales.


Basement Aquifers

The basement rocks generally form low to moderate productivity aquifers where groundwater flow is concentrated in fractures, and often in a weathered mantle, which can develop in the upper few to tens of metres. Boreholes within basement aquifers are typically drilled to depths of 10–70 m, depending on local conditions. Water quality in these aquifers is generally good.


Sedimentary Aquifers

Rocks in the lower, more southerly part, of the Benue Basin form moderately productive aquifers where groundwater flow is concentrated in fractures. Borehole yields typically vary from 2 to 8 litres per second (l/s), but can be much higher or lower than this depending on the degree of fracturing and weathering. Aquifers tend to be localised and unconfined, with boreholes ranging from 40 to 150 m deep. Groundwater from these aquifers can be highly mineralised. Rocks in the Upper Benue Basin typically form low to moderate productivity aquifers, with borehole yields varying between 1 and 5 L/s. Groundwater flow is largely intergranular and boreholes can vary in depth from 30 to 300 m. Groundwater quality is generally good. Rocks in the Nupe Basin form low to moderately productive aquifers. Groundwater flow predominantly occurs through pore spaces in the rocks, which are generally fine grained and slightly cemented, limiting groundwater potential. Where coarser sandstones dominate, yields of 2 to 4 L/s can be achieved; basal conglomerate beds may support higher yields. Borehole yields in rocks of the Sokoto Basin are highly variable, but can be moderate to highly productive where coarser sandstones dominate. Lower sandstones can be confined while upper sandstone layers are typically unconfined. The Chad Formation, found in the Chad Basin, forms a moderate to highly productive aquifer, with yields up to 30 L/s recorded. Groundwater flow is largely intergranular and aquifers can be unconfined or confined depending on local conditions. Deeper sandstone layers are often confined. The Gombe Formation, also in the Chad Basin, has much lower permeability providing yields of around 1 to 5 L/s. Natural water quality from both these formations is generally good.


Igneous Aquifers

Volcanic rocks also occur in Nigeria, forming low to moderately productive aquifers. Borehole yields are typically less than 3 L/s and may be drilled to depths of around 15 to 50 m.


Unconsolidated Aquifers

Unconsolidated rocks, which predominantly occur in the coastal Niger Delta Basin and along major river valleys, form high to very high productivity aquifers. Alluvial aquifers are largely unconfined with shallow water tables and are thickest (15 – 30 m) along the rivers Niger and Benue. In the Niger Delta Basin, the upper Deltaic Formation is unconsolidated and largely unconfined with a shallow water table (0–10 m below ground level).Offodile ME (2002). Groundwater study and development in Nigeria. Mecon Services Ltd, Jos, Nigeria. The older Benin Formation is partly consolidated. It is largely unconfined (locally confined by lower permeability beds) with a water table typically between 3 and 15 m below ground level, but can be as much as 55 m deep. Aquifers in the Niger Delta Basin can provide yields from 3 to 60 L/s with borehole depths ranging from 10 to 800 m. Recharge is mostly directly from rainfall. Water quality issues include salinity, due to intrusion of sea water, iron, and pollution from human activities, particularly in urban areas.


Groundwater Issues


Groundwater Availability

A 1996 survey by the Ministry of Water Resources found only 63% of boreholes in Nigeria were in working order, with many out of action due to pump failure. There are local issues of over-abstraction of groundwater, causing lowering of groundwater levels and, in some cases, land
subsidence Subsidence is a general term for downward vertical movement of the Earth's surface, which can be caused by both natural processes and human activities. Subsidence involves little or no horizontal movement, which distinguishes it from slope move ...
. These are mainly in unconsolidated aquifers in urban areas in the coastal plain in the south, including in Lagos and Port Harcourt. There are issues with drought causing lowering of groundwater levels, both seasonally in dry seasons, and during longer-term periods of low rainfall. This is particularly an issue for local, low storage basement aquifers, both in the north where rainfall is low and in the south, where rainfall is high. The potential
impact of climate change The effects of climate change impact the physical environment, ecosystems and human societies. The environmental effects of climate change are broad and far-reaching. They affect the water cycle, oceans, sea and land ice (glaciers), sea level ...
on groundwater levels, combined with changing water demand, is recognised in the National Water Resources Master Plan.


Groundwater Quality

Groundwater pollution related to human activities (agriculture, domestic waste, industry) are issues in shallow aquifers, particularly permeable unconsolidated deposits, which have little protection from surface activities. Natural groundwater quality issues have also been recorded. Examples of this include high
salinity Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal ...
in shallow alluvial aquifers due to dissolution of evaporate minerals and high
iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...
and
manganese Manganese is a chemical element with the symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of industrial alloy use ...
concentrations in confined aquifers with low dissolved oxygen (i.e. anaerobic).


Transboundary Groundwater

There are several transboundary aquifers in Nigeria: # The Iullemeden, Taoudeni/Tanezrout Aquifer Systems (ITAS), shared by Algeria, Benin, Burkina Faso, Mali, Mauritania, Niger and Nigeria. # The Chad Basin Aquifer, shared by Cameroon, Central African Republic, Chad, Niger and Nigeria. # The Keta Basin Aquifers, shared by Ghana, Togo, Benin and Nigeria. # The Benue Trough, shared by Cameroon and Nigeria # The Rio Del Rey Basin, shared by Cameroon and Nigeria along the coast. The
Lake Chad Basin Commission The Lake Chad Basin Commission (LCBC or CBLT in French) is an intergovernmental organization that oversees water and other natural resource usage in the basin. There are eight member governments—i.e., Cameroon, Chad, Niger, Nigeria, Algeria, the ...
manages issues related to the Chad Basin and a mechanism for the management of the Iullemeden Basin is in development, following a Memorandum of Understanding for establishing an integrated water resources management mechanism for this aquifer.Memorandum of Understanding for the Establishment of a Consultation Mechanism for the Integrated Management of the Water Resources of the Iullemeden Taoudeni/Tanezrouft Aquifer Systems (ITAS) (Algeria, Benin, Burkina Faso, Mali, Mauritani, Niger, Nigeria), 2nd Council of Ministers of GICRESAIT Project, Abuja (Nigeria) 28 March 2014
/ref>


Groundwater Management

There are many bodies with responsibility for groundwater management in Nigeria. They include:
Nigeria Hydrological Services Agency (NIHSA)
whose mandate is water resources (groundwater and surface water) assessment of the country; its quantity, quality, availability and distribution in time and space * Nigeria Integrated Water Resources Management Commission (NIWRMC) that is responsible for regulation of water use and allocation * The state Ministries of Water Resources and their Rural Water Supply and Sanitation Agencies (RUWATSSAN), responsible for provision of water to their various States * The National Water Resources Institute, a parastatal of the Federal Ministry of Water Resources, has responsibility for training, research and data management relating to water in general. * All the River Basin Development Authorities, which are also parastatals of the Federal Ministry of Water Resources involved in the provision of water supply to rural environments within their catchments. Th
Nigerian Association of Hydrogeologists (NAH)
is the professional body concerned with due process and best practices in the exploration, development and management of Nigeria's water resources. The NAH disseminates information on the state of the nation's water resources through annual conferences and a journal, Water Resources. Through membership of the Hydrology and Hydrogeology Subcommittee of the National Technical Committee on Water Resources (NTCWR), the technical arm of the National Council of Water Resources (NCWR), the NAH contributes to the development of water resources policies and legislation, including the Water Resources Act 100 and the Nigerian Standard for Drinking Water Quality. The Nigeria Hydrological Services Agency (NIHSA), an agency of the Federal Ministry of Water Resources, has responsibility for groundwater monitoring. There is a national groundwater level monitoring programme with 43 monitoring points, 32 of which are equipped with data loggers. These are sited in basement and sedimentary aquifers. The frequency of monitoring at sites with data loggers is daily, and sometimes twice daily. NIHSA has implemented a programme of drilling new monitoring boreholes for monitoring groundwater level. The new boreholes so far are focussed on sedimentary aquifers used for urban water supply; with borehole depths of 80 to 100 m. The groundwater level monitoring data are stored at NIHSA headquarters in Abuja. The NIHSA is also responsible for water quality monitoring, but as yet a full programme is not in place due to lack of equipment. The National Water Resources Master Plan recognises current problems in the effective acquisition and management of groundwater data, and recommends strategies for improving this situation.


Sources

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References

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External links

* https://www.bgs.ac.uk/africagroundwateratlas/index.cfm * http://earthwise.bgs.ac.uk/index.php/Hydrogeology_of_Nigeria Hydrogeology Water in Nigeria Geology of Nigeria