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[[Africa Groundwater Atlas Home | Africa Groundwater Atlas]] >> [[Hydrogeology by country | Hydrogeology by country]]  >> Hydrogeology of Niger
 
[[Africa Groundwater Atlas Home | Africa Groundwater Atlas]] >> [[Hydrogeology by country | Hydrogeology by country]]  >> Hydrogeology of Niger
  
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   This page is being updated. Please check back soon for updates.
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   '''Lire cette page en français: [[Hydrogéologie du Niger | Hydrogéologie du Niger]]''' [[File: flag_of_france.png  | 50px]]
 
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[[File:CC-BY-SA_logo_88x31.png | frame | This work is licensed under a [https://creativecommons.org/licenses/by-sa/3.0/ Creative Commons Attribution-ShareAlike 3.0 Unported License]]]
 
  
 
Niger is the largest country in West Africa, with some 80% of its area within the Sahara desert. Since independence from French colonialism in 1958, the country has seen alternate periods of civil and military rule. Currently a multi-party democracy, Niger faces significant development challenges. It has one of the lowest literacy rates in the world.  
 
Niger is the largest country in West Africa, with some 80% of its area within the Sahara desert. Since independence from French colonialism in 1958, the country has seen alternate periods of civil and military rule. Currently a multi-party democracy, Niger faces significant development challenges. It has one of the lowest literacy rates in the world.  
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===General===
 
===General===
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Niger is a landlocked country in West Africa, with mainly gentle relief.
 
  
 
{| class = "wikitable"
 
{| class = "wikitable"
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|Border Countries || Nigeria, Benin, Burkina Faso, Mali, Algeria, Libya, Chad.
 
|Border Countries || Nigeria, Benin, Burkina Faso, Mali, Algeria, Libya, Chad.
 
|-
 
|-
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|Total Surface Area* || 1,266,700 km<sup>2</sup> (126 670 000 ha)
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|Total Surface Area* (km<sup>2</sup>) || 1,266,700
 
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|-
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|Total Population (2015)** || 19,899,000  
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|Total Population (2015)** || 19,899,000
 
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|-
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|Rural Population** (2015) || 16,290,000 (82%)
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|Rural Population** (2015) || 16,290,000
 
|-
 
|-
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|Urban Population** (2015) || 3,609,000 (18%)
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|Urban Population** (2015) || 3,609,000
 
|-
 
|-
 
|Human Development Index (HDI) (highest = 1)** || 0.3483
 
|Human Development Index (HDI) (highest = 1)** || 0.3483
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<nowiki>*</nowiki> Source: World Bank
 
<nowiki>*</nowiki> Source: World Bank
 
<nowiki>**</nowiki> Source: [http://www.fao.org/nr/water/aquastat/main/index.stm FAO Aquastat]
 
<nowiki>**</nowiki> Source: [http://www.fao.org/nr/water/aquastat/main/index.stm FAO Aquastat]
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Niger is a landlocked country in West Africa, with mainly gentle relief.
  
  
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This section provides a summary of the geology of Niger. The geology map below shows a simplified overview of the geology at a national scale. For more information on the datasets used in the map see the [[Geology | the Geology resource page]].
 
This section provides a summary of the geology of Niger. The geology map below shows a simplified overview of the geology at a national scale. For more information on the datasets used in the map see the [[Geology | the Geology resource page]].
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[https://www.bgs.ac.uk/africagroundwateratlas/downloadGIS.html '''Download a GIS shapefile of the Niger geology and hydrogeology map'''].
 
  
 
''Other sources of geological information''
 
''Other sources of geological information''
  
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A [https://inis.iaea.org/search/searchsinglerecord.aspx?recordsFor=SingleRecord&RN=39112006 geological map of the Republic of Niger at 1: 2 million scale], published in 1966, was published in paper form, and may be available from the Centre de Recherche Geologique et Miniere in Niamey.  
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A [https://inis.iaea.org/search/search.aspx?orig_q=RN:3911200 geological map of the Republic of Niger at 1: 2 million scale], published in 1966, was published in paper form, and may be available from the Centre de Recherche Geologique et Miniere in Niamey.  
  
 
A [http://www.brgm.eu/project/geological-mining-information-system-niger BRGM project] in 2011 helped to set up a geographical information system (GIS) for geological and mining data, although it may not still be available.
 
A [http://www.brgm.eu/project/geological-mining-information-system-niger BRGM project] in 2011 helped to set up a geographical information system (GIS) for geological and mining data, although it may not still be available.
  
  
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[[File:Niger_Geology4.png | center | thumb| 500px | Geology of Niger at 1:5 million scale. Based on map described by Persits et al. 2002 / Furon and Lombard 1964. For more information on the map development and datasets see the [[Geology | geology resource page]]. [https://www.bgs.ac.uk/africagroundwateratlas/downloadGIS.html Download a GIS shapefile of the Niger geology and hydrogeology map].]]
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[[File:Niger_Geology2.png | center | thumb| 500px | Geology of Niger at 1:5 million scale. Developed from USGS map (Persits et al. 2002). For more information on the map development and datasets see the [[Geology | geology resource page]].]]
  
 
{| class = "wikitable"
 
{| class = "wikitable"
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|-
 
|-
 
|cross-basin
 
|cross-basin
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||Unconsolidated Quaternary, undifferentiated
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||Quaternary
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||Unconsolidated sediments of Quaternary age cover much of the surface outcrop of Chad. Within the Chad Basin (see below), most Quaternary sediments belong to the Chad Formation. Within the Iullemeden Basin (see below) are extensive aeolian (dune) sands and alluvial sands and gravels in river valleys. There are also small outcrops of lacustrine silts and clays and evaporite deposits in former lake beds.  
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||Away from the Chad and Iullemedan Basins (see below), smaller outcrops of Quaternary sediments can be found, including alluvial sands and gravels in river valleys; lacustrine silts and clays and evaporite deposits in former lake beds; and some small areas of aeolian dune sands.  
 
|-
 
|-
 
|Chad Basin
 
|Chad Basin
 
||Cretaceous-Quaternary
 
||Cretaceous-Quaternary
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||The Chad Basin is a major geological feature: a sedimentary depositional basin that extends over large parts of a number of countries including Chad and Nigeria. In Niger, the Chad Basin covers most of the east and north of the country. The basin contains a great thickness of sedimentary rocks dating from the Cretaceous to Quaternary in age. These are more than 3,500 m thick at the thickest known points, but may be more. These sedimentary rocks are underlain by Precambrian bedrock.  
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||The Chad Basin is a major geological feature: a sedimentary depositional basin that extends over large parts of a number of countries including Chad and Nigeria. In Niger, the Chad Basin extends over much of the east and north of the country. The Basin contains a great thickness of sedimentary rocks dating from the Cretaceous to Quaternary in age - it is more than 3,500 m thick at its thickest known points, although the total thickness in Niger is uncertain. These sedimentary rocks are underlain by Precambrian bedrock.  
  
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''Quaternary:'' the uppermost and youngest sediments in the Chad Basin belong to the Chad Formation, and are largely of Quaternary age. These range from a few tens of metres up to many hundreds of metres thick. The Chad Formation consists of unconsolidated fine to coarse grained sands and gravels with sandy clays. These include extensive aeolian (dune) sands, and relatively extensive clayey to sandy aluvial sediments in active and abandoned river channels. There are also lacustrine (lake and lake-margin), alluvial fan and deltaic deposits. Much of the sequence is sandy or gravelly, but there are frequent lacustrine clay layers. Abrupt changes in clay and sand content are common, and the sediments usually occur as overlapping lenses.  
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The youngest and uppermost formation is the Chad Formation, largely of Quaternary age, which can reach many hundreds of metres thick. It consists of unconsolidated fine to coarse grained sands and gravels with sandy clays. These include extensive aeolian (dune) sands, and also lacustrine (lake and lake-margin), alluvial fan and deltaic deposits. Much of the sequence is sandy or gravelly, but there are frequent lacustrine clay layers. Abrupt changes in clay and sand content are common, and the sediments usually occur as overlapping lenses.  
  
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''Tertiary:'' the Chad Formation is underlain by the Continental Terminal formation, largely of Tertiary age, which consists of alternating, usually loosely consolidated, sandstones, siltstones, shales and mudstones.
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The Chad Formation is underlain by the Continental Terminal formation, largely of Tertiary age, which consists of alternating, usually loosely consolidated, sandstones, siltstones, shales and mudstones.
  
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''Cretaceous:'' below the Continental Terminal there may be consolidated sedimentary rocks of Cretaceous age, dominantly marine but some continental sediments - including sandstones, siltsones, marls/calcareous mudstones and limestones.
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Below the Continental Terminal there may be consolidated sedimentary rocks of Cretaceous age, dominantly marine but some continental sediments - including sandstones, siltsones, marls/calcareous mudstones and limestones.
 
|-
 
|-
 
|Iullemeden (also called Niger) Basin
 
|Iullemeden (also called Niger) Basin
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||The Iullemeden Basin lies immediately west of the Chad Basin and covers most of the western part of Niger. The Basin extends beyond Niger to parts of Mali, Benin and northwest Nigeria (it is called the Sokoto Basin in northwestern Nigeria). The total sedimentary sequence in the basin reaches several thousand metres thick.
 
||The Iullemeden Basin lies immediately west of the Chad Basin and covers most of the western part of Niger. The Basin extends beyond Niger to parts of Mali, Benin and northwest Nigeria (it is called the Sokoto Basin in northwestern Nigeria). The total sedimentary sequence in the basin reaches several thousand metres thick.
  
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''Quaternary'': the youngest and uppermost sediments in the basin are unconsolidated Quaternary sediments, including extensive aeolian (dune) sands and alluvial sediments - extensive sands and gravels. and more minor silts and clays. These are often thin, up to few metres thick at most.
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The youngest and uppermost sediments in the basin are unconsolidated Quaternary sediments, including extensive aeolian (dune) sands and alluvial deposits.  
  
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''Tertiary'': sedimentary rocks of Tertiary age include poorly-consolidated/loosely cemented clays, siltstones and sandstones of continental origin. In some places are chalky limestones. The sandstone parts of this sequence form part of the so-named regional Continental Terminal 3 aquifer, the base of which is formed by a continuous clayey layer of few tens
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Below this are consolidated Tertiary sedimentary rocks: chalky limestones, mudstones and shales.
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of metres thick (Vouillamoz et al, 2007).
 
  
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''Cretaceous'': the lower parts of the Iullemeden Basin sequence are of Cretaceous age, including: Upper Cretaceous argillaceous siltstones and clays; Cenomanian to Turonian marine and lagoonal limestones, dolomitic limestones and sandstones; and Middle to Upper Cretaceous coarse grained sandstones.  
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The lower parts of the Iullemeden Basin sequence are rocks of Cretaceous age, including: argillaceous siltstones and clays of Upper Cretaceous age; marine and lagoonal limestones, dolomitic limestones and sandstones of Cenomanian to Turonian age; coarse grained sandstones of Middle to Upper Cretaceous age; and sandstones and mudstones of Continental Terminal/Continental Intercalaire type.  
 
|-
 
|-
 
|Mesozoic-Palaeozoic
 
|Mesozoic-Palaeozoic
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||Older sedimentary rocks crop out most on the northeast of the country, and in parts of the north, adjacent to Precambrian basement. These rocks include sandstones and siltstones of Triassic and Jurassic age; Carboniferous calcareous sandstones; Devonian argillaceous sandstones; and Ordovician sandstones and limestones.
 
||Older sedimentary rocks crop out most on the northeast of the country, and in parts of the north, adjacent to Precambrian basement. These rocks include sandstones and siltstones of Triassic and Jurassic age; Carboniferous calcareous sandstones; Devonian argillaceous sandstones; and Ordovician sandstones and limestones.
 
|-
 
|-
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!colspan="4"| Igneous
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!colspan="4"| Igneous - largely volcanic
 
|-
 
|-
 
|
 
|
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||Mesozoic-Quaternary
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||
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||Igneous rocks in Niger are not widespread but are relatively well known geologically. Mesozoic to Tertiary igneous activity produced sequences of magmatic rocks that are now exposed as ring complexes, which can be seen clearly on the geology map in central Niger within the main area of Precambrian rocks. Surrounding these are smaller outcrops of Quaternary volcanic rocks.
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||
 
|-
 
|-
 
!colspan="4"|Basement
 
!colspan="4"|Basement
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|
 
|
 
||Precambrian
 
||Precambrian
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||Plutonic grantitic and gneissose and undifferentiated crystalline metamorphic rocks. These crop out in the far west of the country and form the higher ground in the centre of Niger.
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||Plutonic grantitic and gneissose and undifferentiated crystalline metamorphic rocks.
 
|}
 
|}
  
 
==Hydrogeology==
 
==Hydrogeology==
  
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This section provides a summary of the hydrogeology of the main aquifers in Niger. More detailed information on specific aquifers can be found in some of the references listed at the bottom of this page.
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This section provides a summary of the hydrogeology of the main aquifers in Niger. More information is available in the report [https://www.bgs.ac.uk/africaGroundwaterAtlas/atlas.cfc?method=ViewDetails&id=AGLA060045 UN (1988)] (see References section, below).  
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The hydrogeology map shows a simplified overview of the type and productivity of the main aquifers at a national scale (see the [[Africa Groundwater Atlas Hydrogeology Maps | Hydrogeology map resource page]] for more details).
 
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[https://www.bgs.ac.uk/africagroundwateratlas/downloadGIS.html '''Download a GIS shapefile of the Niger geology and hydrogeology map'''].
 
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[[File:Niger_Hydrogeology4.png | center | thumb| 500px | Hydrogeology of Niger at 1:5 million scale. For more information on how the map was developed see the [[Africa Groundwater Atlas Hydrogeology Maps | Hydrogeology map]] resource page. [https://www.bgs.ac.uk/africagroundwateratlas/downloadGIS.html Download a GIS shapefile of the Niger geology and hydrogeology map].]].
 
  
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====Summary====
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The most extensive and productive aquifers of Niger are sedimentary formations known as the Continental Terminal and Continental Intercalaire, across much of the west (the Iullemeden Basin) and east (the Chad Basin) of the country. Weathered Precambrian crystalline basement aquifers also play an important role in the supply of water to rural centres, particularly those of Liptako and Damagaram-Mounio. Other significant aquifers are the Quaternary and Tertiary aquifers in the Lake Chad basin and the Agadez sandstone aquifer.
  
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There are three main types of aquifer in Niger:
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The hydrogeology map shows a simplified overview of the type and productivity of the main aquifers at a national scale (see the [[Hydrogeology Map | Hydrogeology map resource page]] for more details).
  
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:- '''Unconsolidated sediments''' dominated by sands, sometimes with gravel, of alluvial or aeolian origin. Alluvial sediments in large valleys can form productive local aquifers. More extensive dune sands, such as the thick Chad Formation in the Chad Basin, form a regionally important aquifer.
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[[File:Niger_Hydrogeology2.png | center | thumb| 500px | Hydrogeology of Niger at 1:5 million scale. For more information on how the map was developed see the [[Hydrogeology Map | Hydrogeology map]] resource page]].
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:- Loosely to strongly '''consolidated sedimentary rocks''': sandstones, limestones and siltstones of Mesozoic (Cretaceous-Tertiary) and Palaeozoic age.
 
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:- '''Precambrian Basement''' weathered/fractured aquifers, used locally in parts of western and central Niger.  
 
  
−
The most extensive and productive aquifers of Niger are sedimentary formations known as the Continental Terminal and Continental Intercalaire, of Cretaceous-Tertiary age, which occur in two major sedimentary basins: the Chad Basin, which extends across much of the east of Niger, and the Iullemeden Basin, which covers much of the west of the country. In some areas, these aquifers are overlain by, and in hydraulic continuity with, thick and often extensive unconsolidated Quaternary aquifers, including the extensive Chad Formation in the Chad Basin.
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====Unconsolidated====
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====Unconsolidated Sedimentary====
 
 
{| class = "wikitable"
 
{| class = "wikitable"
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|Named Aquifers||Aquifer Productivity||Description||Water quality  
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|Named Aquifers||Period||General Description||Water quality  
 
|-
 
|-
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|Valley alluvial sediments; local aeolian deposits
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|Alluvium, aeolian deposits
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||Variable: often Moderate to High; sometimes Low
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||Quaternary
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||Where thick enough and dominated by sand and/or gravel, can be highly permeable with high storage potential. Alluvial deposits in valleys typically have shallow water tables and can form productive local aquifers. Small, local aeolian sand deposits on plateaus can be dry.  
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||Where thick enough and dominated by sand and/or gravel, can be highly permeable with high storage potential. Alluvial deposits in valleys typically have shallow water tables and can form productive local aquifers. Aeolian deposits on plateaus can be dry.  
 
||  
 
||  
 +
|}
 +
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==== Sedimentary - Intergranular Flow====
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{| class = "wikitable"
 +
|Named Aquifers||Period||General Description||Water quality
 
|-
 
|-
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|Chad Formation in the Chad Basin
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|Chad Basin (Chad Formation)
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||Variable: Moderate to High; sometimes Low
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||Quaternary
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||A heterogeneous aquifer of unconsolidated or loosely consolidated, interbedded sandy and clayey layers. Groundwater storage and flow occur preferentially in sandy layers. Individual sandy layers can be confined by overlying clayey layers, forming a multilayered aquifer that can be artesian in some cases.
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||Overall, dominated by loosely consolidated sands with significant permeability, forming a highly productive aquifer. Some areas are dominated by low permeability clays. Where clays are interbedded with sands, it forms a multilayered aquifer, sometimes artesian.  
  
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A study in the Komadugu Yobe aquifer estimated the porosity of the Chad Formation, to between 50 and 100 m depth, at between 20 and 28%, and estimated a range of transmissivity values from 160 to 575 m<sup>2</sup>/day, with a mean transmissivity of 260 m<sup>2</sup>/day (Descloitres et al. 2013). Other transmissivity values obtained from test pumping in the Chad Formation are 3 m<sup>2</sup>/day, 100 m<sup>2</sup>/day and 250 m<sup>2</sup>/day (Descloitres et al. 2013), varying depending on whether the tested part of the aquifer was dominated by aeolian sand or by alluvial, often clayey sand.
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Surface layers recharged by direct rainfall infiltration; deeper layers have more restricted recharge.
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||  
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Recharge is low, estimated as only a few millimetres per year (e.g. Leduc et al. 2000). Residence times for groundwater in the aquifer have been calculated at 1000 to 2000 years (Leduc et al 2000). Recharge occurs both directly from intermittent rains, and indirectly via leakage from rivers and, close to Lake Chad, sometimes also from the lake. Where the upper layers are dominated by sands, recharge is largely unrestricted, and so these layers are vulnerable to pollution. Recharge to deeper sandy layers can be restricted by overlying clayey layers, which also provide some protection from pollution.  
 
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||Close to large rivers, where groundwater may be in hydraulic contact with river water, groundwater salinity is thought to be often low. For example, in the Komadugu Yobe aquifer, the SEC (specific electrical conductivity) of groundwater close to the Komadugu Yobe River is less than 200 uS/cm, but increases with distance from the river, to a maximum of more than 3000 uS/cm in the centre of the Kadzell depression (Descloitres et al. 2013).
 
 
|}
 
|}
  
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====Sedimentary - Intergranular Flow====
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==== Sedimentary - Intergranular & Fracture Flow====
 
{| class = "wikitable"
 
{| class = "wikitable"
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|Named Aquifers||Aquifer Productivity||Description||Water quality  
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|Named Aquifers||Period||General Description||Water quality  
 
|-
 
|-
−
|Chad Basin Tertiary-Cretaceous (including Continental Terminal)
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|Chad Basin (Continental Terminal, Cretaceous-Tertiary undifferentiated)
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||Moderate to High
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||Tertiary
 
||Overall, dominated by sandstones with significant permeability, but some areas dominated by low permeability siltstones and clays. Where clays are interbedded with sandstones, it forms a multilayered aquifer, sometimes artesian.
 
||Overall, dominated by sandstones with significant permeability, but some areas dominated by low permeability siltstones and clays. Where clays are interbedded with sandstones, it forms a multilayered aquifer, sometimes artesian.
  
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Low and intermittent rainfall means there is low direct recharge, even to unconfined parts of the aquifer. A significant proportion of the groundwater stored in the aquifer is fossil water, recharged thousands of years ago.
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Surface layers recharged by direct rainfall infiltration; deeper layers have more restricted recharge.
 
||  
 
||  
 
|-
 
|-
−
|Iullemeden (Niger) Basin Tertiary-Cretaceous (largely Continental Terminal; at depth may also include aquifers known as Continental Intercalaire)
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|Iullemeden (Niger) Basin (largely Continental Terminal, Continental Intercalaire)
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||Moderate to High
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||Cretaceous
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||Sandstones, often coarse grained, and clays, limestones and silts. The Continental Terminal aquifer extends across the Iullemeden Basin and is up to 450 m thick in its central part. It either overlies Continental Intercalaire rocks or directly overlies Precambrian basement. Andrews et al (1994) describe aquifer rocks of the older Continental Intercalaire in the northern part of the Iullemeden Basin. The Continental Terminal often forms a multi-layered aquifer, with thick sandstone (often fine-grained and/or silty) units forming aquifer layers, interspersed by lower permeability clayey, silty layers which often range from a few metres to around 20 m thick.
+
||Sandstones, often coarse grained, and clays, limestones and silts. Unconfined in its eastern part, becoming confined towards the west below younger clays, with artesian conditions found especially in deep valleys. The Tegama sandstones form a particularly productive aquifer unit, about 500 m thick, but buried beneath about 500 m of younger cover. Low direct recharge to unconfined areas because of low rainfall.  
−
 
+
||  
−
The average depth to water table in the uppermost, unconfined aquifer was 35 m, but it ranges from near ground level (beneath the lowest elevation ground) to 75 m deep (under plateau areas) (Favreau et al. 2003, Le Gal La Salle et al. 2001). The uppermost aquifer is usually unconfined, but deeper aquifer layers are often confined and can have artesian conditions. A rising water table has been seen in many areas in past decades (a 4 m rise from 1963 to 2007), despite a ∼23% deficit in monsoonal rainfall from 1970 to 1998. Low and intermittent rainfall means there is relatively low direct recharge, even to unconfined parts of the aquifer, and a significant proportion of the groundwater stored in the aquifer is fossil water, recharged thousands of years ago. However, increased recharge rates have been seen since the 1950s - from about 1-5 mm/year to more than 20 mm/year in the 1990s - which are linked to intense land clearing that has enhanced runoff and groundwater recharge (Favreau et al, 2002, 2009; Leblanc et al. 2008).
 
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||The groundwater chemistry is often mildly acidic (pH between 5.0 and 6.0) and oxidising (Eh values between 300 and 500 mV). Total dissolved solids (TDS) values are generally low, with a median of 50 mg/l, consistent with the quartzitic nature of the aquifer. The dominant ions are NO<sub>3</sub>, HCO<sub>3</sub>, Na and Ca (Favreau et al. 2003). High nitrate concentrations (up to 100 mg/l) are seen close to surface water ponds that are sources of recharge, and are thought to be largely naturally derived from the soil and related to an enhanced nitrogen flux following land clearance (Favreau et al. 2003).
 
−
|}
 
−
 
 
−
==== Sedimentary - Intergranular & Fracture Flow====
 
−
{| class = "wikitable"
 
−
|Named Aquifers||Aquifer Productivity||Description||Water quality
 
 
|-
 
|-
−
|Palaeozoic-Mesozoic sedimentary (including rocks known as the Continental Intercalaire)
+
|Palaeozoic-Mesozoic sedimentary  
−
||Moderate to High
+
||Ordovician - Jurassic
 
||Shallower, younger sandstones tend to show more intergranular flow; older, deeper sandstones and limestones tend to be dominated by fracture flow. Aquifers can be very deep - e.g. an Ordovician aquifer at more than 800 m deep.  
 
||Shallower, younger sandstones tend to show more intergranular flow; older, deeper sandstones and limestones tend to be dominated by fracture flow. Aquifers can be very deep - e.g. an Ordovician aquifer at more than 800 m deep.  
  
−
Shallower aquifers typically form unconfined aquifer, with recharge from direct rainfall infiltration and from infiltration of ephemeral river flow. Deeper aquifers are often confined, and artesian - e.g., the Carboniferous Farazekat sandstone aquifer has artesian flows of between 3 and 30 m³/hour. Deeper aquifers have relatively low recharge.
+
Shallower aquifers typically form unconfined aquifer, with recharge from direct rainfall infiltration and from infilration of ephemeral river flow. Deeper aquifers are often confined, and artesian - e.g., the Carboniferous Farazekat sandstone aquifer has artesian flows of between 3 and 30 m³/hour. Deeper aquifers have relatively low recharge.  
−
 
+
||Groundwater in deeper aquifers can be highly mineralised.  
−
Andrews et al (1994) describe a Continental Intercalaire aquifer in the northern part of the Iullemeden Basin, west of the Air mountains, with an aquifer sequence from Cretaceous to Permian in age. This sequence included the Teloua  sandstones (Triassic/Lower Jurassic) and a multilayer aquifer of the largely Jurassic Agadez and Dabla Sandstones. The same study also investigated groundwater from deep boreholes in Carboniferous age aquifers.  
 
−
||Groundwater in deeper aquifers can be highly mineralised. The chemistry of groundwater in the Agadez-Dable sandstone aquifer in northern Niger is described in detail in Andrews et al 1994: in summary, it was typically slightly alkaline and moderately mineralised where the aquifer is at outcrop (pH 7.3 - 8.0; conductivity (specific electrical conductivity or SEC) 340 - 700 uS/cm) and more alkaline and mineralised where the aquifer is confined (pH 7.3 - 9.5; SEC 625 - 6000 uS/cm). Oxygen concentrations in groundwater were generally low throughout the aquifer.
 
 
|}
 
|}
  
−
====Igneous====
 
−
{| class = "wikitable"
 
−
|Named Aquifers||Aquifer Productivity||Description
 
−
|-
 
−
|Igneous
 
−
||Probably Low to Moderate
 
−
||Little is known of the aquifer properties of the igneous rocks in Niger. They are likely to form similarly low productivity, local aquifers as the Precambrian basement, although the detailed pattern of fracturing and weathering may be different. The youngest, Quaternary, volcanic rocks may be more fractured and have higher permeability and better groundwater potential. 
 
−
|}
 
  
 
====Basement====
 
====Basement====
 
{| class = "wikitable"
 
{| class = "wikitable"
−
|Named Aquifers||Aquifer Productivity||Description||Water quality  
+
|Named Aquifers||Period||General Description||Water quality  
 
|-
 
|-
−
|Precambrian Basement
+
|Basement
−
||Low
+
||Precambrian
−
||Discontinuous, low productivity aquifers controlled by the thickness and nature of weathering (regolith) and the presence of deeper fractures. Where weathered products are dominated by argillaceous material, yields are particularly low. Weathered Precambrian basement aquifers play an important role in the supply of water to some rural centres, particularly in Liptako and Damagaram-Mounio.
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||Discontinuous, low productivity aquifers controlled by the thickness and nature of weathering (regolith) and the presence of deeper fractures. Where weathered products are dominated by argillaceous material, yields are particularly low.  
 
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Niger has vast quantities of groundwater stored in deep sedimentary aquifers, much of which is likely to be ancient 'fossil' water that is not actively recharged because modern rainfall is so low. Shallower aquifers, particularly alluvial aquifers in valleys and local weathered (regolith) aquifers in basement, store much smaller amounts of groundwater, but are recharged annually by seasonal rainfall, on which they rely very heavily. In 1995, OSS estimated that Niger used less than 10% of its total groundwater resources; by 2003, this was estimated at 20% (Conseil National de l'Environnement Pour un Developpement Durable).  
 
Niger has vast quantities of groundwater stored in deep sedimentary aquifers, much of which is likely to be ancient 'fossil' water that is not actively recharged because modern rainfall is so low. Shallower aquifers, particularly alluvial aquifers in valleys and local weathered (regolith) aquifers in basement, store much smaller amounts of groundwater, but are recharged annually by seasonal rainfall, on which they rely very heavily. In 1995, OSS estimated that Niger used less than 10% of its total groundwater resources; by 2003, this was estimated at 20% (Conseil National de l'Environnement Pour un Developpement Durable).  
  
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Some of Niger's groundwater is highly mineralised, related to high evaporation (in shallow aquifers) and/or to age and dissolution of aquifer minerals; however, this is not recognised as a widespread problem (UNICEF 2010). Borehole databases indicate that fresh groundwater occurs across the southern region; there is not enough information for other areas to assess the situation (UNICEF 2010). There are known local problems of bacterial and nitrate contamination, related to human and animal waste disposal (UNICEF 2010). High nitrate concentrations in groundwater also occur naturally in some areas, such as widely in the Continental Terminal aquifer in the Iullemeden Basin, relating to a nitrogen flux from intensive land clearance in this area over decades (Favreau et al. 2003).
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Some of Niger's groundwater is highly mineralised, related to high evaporation (in shallow aquifers) and/or to age and dissolution of aquifer minerals; however, this is not recognised as a widespread problem (UNICEF 2010). Borehole databases indicate that fresh groundwater occurs across the southern region; there is not enough information for other areas to assess the situation (UNICEF 2010). There are also known local problems of bacterial and nitrate contamination, related to human and animal waste disposal (UNICEF 2010).
  
 
==Groundwater use and management==
 
==Groundwater use and management==
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=== Groundwater management and monitoring===
 
=== Groundwater management and monitoring===
  
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A recent German Development Cooperation project was run by [https://www.bgr.bund.de/EN/Home/homepage_node_en.html;jsessionid=2F3430C628B5BEA8AFFEFC4D4B9CA9C3.2_cid284 BGR] to investigate groundwater in the capital, Niamay, and to provide advice on groundwater protection to the Niger Basin Authority. The project was called the [http://www.bgr.bund.de/EN/Themen/Wasser/Projekte/laufend/TZ/Niger/abn_fb_en.html '''Integrated Water Resources Management Programme''']. Project work included the collection and assessment of groundwater data and maps in the Niger basin and the development of a groundwater database, which forms the basis for future development of a basin hydrogeological map and groundwater modelling. The project also started groundwater level monitoring using existing boreholes, and used the new monitoring data to create groundwater level contour maps for aquifers around Niamay (Menge 2013, Vassolo et al. 2015).  
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A recent German Development Cooperation project, the [http://www.bgr.bund.de/EN/Themen/Wasser/Projekte/laufend/TZ/Niger/abn_fb_en.html Integrated Water Resources Management Programme], is providing advice to the Niger Basin Authority on groundwater protection. Project work has included the collection and assessment of groundwater data and maps in the Niger basin in order to develop a groundwater database, and to form the basis for future development of a basin hydrogeological map and groundwater modelling. The project also initiated groundwater level monitoring using existing boreholes, using collected data to create groundwater level contour maps for aquifers around Niamay (Menge 2013, Vassolo et al. 2015).  
  
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Information on water boreholes and hand dug wells is stored in at least two government databases: one for the central region, and one that in theory covers the whole country, although there is little groundwater source data for the north and east of Niger. Of a total of more than 24,000 wells and boreholes identified by the Ministry of Water, a UNICEF study (2010) identified some 11,000 for which some information was available. Many of these, but not all, had information on borehole rest (static) water level, but none had geological log or water quality information.
+
Information on water boreholes and hand dug wells is stored in at least two databases, one for the central region, and one that in theory covers the whole country, although there is little groundwater source data for the north and east of Niger. Of a total of more than 24,000 wells and boreholes identified by the Ministry of Water, a UNICEF study (2010) identified some 11,000 for which some information was available. Many of these, but not all, had information on borehole rest (static) water level, but none had geological log or water quality information.  
  
 
=== Transboundary aquifers===
 
=== Transboundary aquifers===
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The Iullemeden aquifer system (SAI), shared by Mali, Niger and Nigeria, includes two major sedimentary aquifers: the Continental Intercalaire and the Continental Terminal. It covers an area of ​​approximately 500 000 sq km, and is the main source of sustainable water for the vast majority of the populations of this region. The Sahel and Sahara Observatory (OSS) initiated and implemented the SAI project between Niger, Mali and Nigeria, and set up joint a consultation structure in 2008.
 
The Iullemeden aquifer system (SAI), shared by Mali, Niger and Nigeria, includes two major sedimentary aquifers: the Continental Intercalaire and the Continental Terminal. It covers an area of ​​approximately 500 000 sq km, and is the main source of sustainable water for the vast majority of the populations of this region. The Sahel and Sahara Observatory (OSS) initiated and implemented the SAI project between Niger, Mali and Nigeria, and set up joint a consultation structure in 2008.
  
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For more information about transboundary aquifers generally, please see the [[Transboundary aquifers | Transboundary aquifers resources page]].
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For further information about transboundary aquifers, please see the [[Transboundary aquifers | Transboundary aquifers resources page]].
  
 
==References==
 
==References==
  
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The following references provide more information on the geology and hydrogeology of Niger. Many of these, and others, can also be accessed through the [https://www.bgs.ac.uk/africaGroundwaterAtlas/atlas.cfc?method=listResults&title_search=&author_search=&category_search=&country_search=NE&placeboolean=AND&singlecountry=1 Africa Groundwater Literature Archive].
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The following references provide more information on the geology and hydrogeology of Niger. Most of these, and others, can also be accessed through the [https://www.bgs.ac.uk/africaGroundwaterAtlas/atlas.cfc?method=listResults&title_search=&author_search=&category_search=&country_search=NE&placeboolean=AND&singlecountry=1 Africa Groundwater Literature Archive].
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Andrews JN, Fontes J-C, Aranyossy J-F, Dodo A, Edmunds  WMA and A. Travi JY. 1994. [https://doi.org/10.1029/93WR02226  The evolution of alkaline groundwaters in the continental intercalaire aquifer of the Irhazer Plain, Niger]. Water Resources Research 30 (1), 45-61
 
  
 
Chippaux JP, Houssier S, Gross P, Bouvier C and Brissaud F. 2002. [https://www.ncbi.nlm.nih.gov/pubmed/12145956 Pollution of the groundwater in the city of Niamey, Niger]. Bull Soc Pathol Exot. 95(2), 119-23.
 
Chippaux JP, Houssier S, Gross P, Bouvier C and Brissaud F. 2002. [https://www.ncbi.nlm.nih.gov/pubmed/12145956 Pollution of the groundwater in the city of Niamey, Niger]. Bull Soc Pathol Exot. 95(2), 119-23.
  
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Descloitres M, Chalikakis K, Legchenkoa A, Moussa, Genthon P, Favreau G, Le Coz M, Boucher M et Oï M. 2013. [https://doi.org/10.1016/j.jafrearsci.2013.07.006 Investigation of groundwater resources in the Komadugu Yobe Valley (Lake Chad Basin, Niger) using MRS and TDEM methods]. Journal of African Earth Sciences 87, 71-85.  
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Descloitres M, Chalikakis K, Legchenkoa A, Moussa, Genthon P, Favreaud G, Le Coz M, Boucher M et Oï M. 2013. [https://doi.org/10.1016/j.jafrearsci.2013.07.006 Investigation of groundwater resources in the Komadugu Yobe Valley (Lake Chad Basin, Niger) using MRS and TDEM methods]. Journal of African Earth Sciences 87, 71-85.  
  
 
Favreau G, Leduc C, Seidel JL, Ousmane SD and Mariotti ANDRÉ. 2003. [http://hydrologie.org/redbooks/a278/iahs_278_163.pdf  Land clearance and nitrate-rich groundwater in a Sahelian aquifer, Niger]. International Association of Hydrological Sciences 278, 163-167.  
 
Favreau G, Leduc C, Seidel JL, Ousmane SD and Mariotti ANDRÉ. 2003. [http://hydrologie.org/redbooks/a278/iahs_278_163.pdf  Land clearance and nitrate-rich groundwater in a Sahelian aquifer, Niger]. International Association of Hydrological Sciences 278, 163-167.  
  
 
Favreau G, Cappelaere B, Massuel S, Leblanc M, Boucher M, Boulain N and Leduc C. 2009. [http://onlinelibrary.wiley.com/doi/10.1029/2007WR006785/abstract  Land clearing, climate variability, and water resources increase in semiarid southwest Niger: A review]. Water Resources Research, 45(7).
 
Favreau G, Cappelaere B, Massuel S, Leblanc M, Boucher M, Boulain N and Leduc C. 2009. [http://onlinelibrary.wiley.com/doi/10.1029/2007WR006785/abstract  Land clearing, climate variability, and water resources increase in semiarid southwest Niger: A review]. Water Resources Research, 45(7).
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Gaultier G. 2004. Recharge et paléo-recharge d’une nappe libre en milieu sahélien (Niger oriental): approches géochimique et hydrodynamique. PhD Thesis (Thèse de doctorat), Université de Paris-Sud, Orsay, France, 165pp.
 
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Lang J, Kogbe C, Alidou S, Alzouma KA, Bellion G, Dubois D, Durand A, Guiraud R, Houessou A, De Klasz I, Romann E, Salard-Cheboldaeff M and Trichet, J. 1990. The Continental Terminal in West Africa. Journal of African Earth Sciences 10 (1–2), 79–99.
 
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Le Gal La Salle C, Marlin C, Leduc C, Taupin JD, Massault M and Favreau G, 2001. [https://doi.org/10.1016/S0022-1694(01)00491-7 Renewal rate estimation of groundwater based on radioactive tracers (3H, 14C) in an unconfined aquifer in a semi-arid area, Iullemeden Basin, Niger]. Journal of Hydrology 254 (1–4), 145-156
 
  
 
Leblanc MJ, Favreau G, Massuel S, Tweed SO, Loireau M and Cappelaere B. 2008. [http://www.sciencedirect.com/science/article/pii/S0921818107001336 Land clearance and hydrological change in the Sahel: SW Niger]. Global and Planetary Change, 61(3), 135-150.  
 
Leblanc MJ, Favreau G, Massuel S, Tweed SO, Loireau M and Cappelaere B. 2008. [http://www.sciencedirect.com/science/article/pii/S0921818107001336 Land clearance and hydrological change in the Sahel: SW Niger]. Global and Planetary Change, 61(3), 135-150.  
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Vassolo S, Schuler P, Guero A, Rabé S, Mounkaila M and Menge S. 2015. [http://www.bgr.bund.de/EN/Themen/Wasser/Projekte/laufend/TZ/Niger/rapport04.pdf?__blob=publicationFile&v=3 Caractérisation des eaux souterraines de la région de Niamey, Niger].Hannover: 50 pp, Hannover.
 
Vassolo S, Schuler P, Guero A, Rabé S, Mounkaila M and Menge S. 2015. [http://www.bgr.bund.de/EN/Themen/Wasser/Projekte/laufend/TZ/Niger/rapport04.pdf?__blob=publicationFile&v=3 Caractérisation des eaux souterraines de la région de Niamey, Niger].Hannover: 50 pp, Hannover.
  
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Werth S, White D and Bliss D W. 2017. [https://doi.org/10.1002/2017JB014845 GRACE Detected Rise of Groundwater in the Sahelian Niger River Basin]. Journal of Geophysical Research 122(12), 10,459-10,477
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==Return to the index pages==
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[[Africa Groundwater Atlas Home | Africa Groundwater Atlas]] >> [[Hydrogeology by country | Hydrogeology by country]] >> Hydrogeology of Niger
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Zaïri R. 2008. Etude géochimique et hydrodynamique de la nappe libre du bassin du lac Tchad dans les régions de Diffa (Niger oriental) et du Bornou (nord-est du Nigéria). PhD Thesis, Université Montpellier II, Montpellier, France, 225pp
 
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Return to the index pages
 
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[[Africa Groundwater Atlas Home | Africa Groundwater Atlas]] >> [[Hydrogeology by country | Hydrogeology by country]]  
 
  
  

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