Difference between revisions of "Africa Groundwater Atlas Hydrogeology Maps"

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   This page is being revised. Please check back soon for updates
 
   This page is being revised. Please check back soon for updates
 
    
 
    
==The Atlas Country Hydrogeology Maps==
+
==The Africa Groundwater Atlas Country Hydrogeology Maps==
  
 
The country hydrogeology  maps in this Atlas provide an overview of the hydrogeology and geology of each of 48 countries in Africa, at 1:5 million scale. The maps will be available to download as digital, GIS-enabled shapefiles with two themes:  
 
The country hydrogeology  maps in this Atlas provide an overview of the hydrogeology and geology of each of 48 countries in Africa, at 1:5 million scale. The maps will be available to download as digital, GIS-enabled shapefiles with two themes:  
  
* '''geology''', with geological interpretations that are particularly relevant to hydrogeology; and
+
* '''geology''', with geological categories that reflect significant hydrogeological units (MacDonald et al. 2010); and  
* a combined classification of '''aquifer type''' and '''aquifer productivity'''.
+
* '''hydrogeology''', with categories that combine '''aquifer type''' and '''aquifer productivity'''.
  
 
More detail on these classifications is below.  
 
More detail on these classifications is below.  
  
====Benefits of the Atlas country hydrogeology maps====
+
===Who might use the Atlas country hydrogeology maps===
  
These maps provide an essential national overview of the groundwater resources of each country. For some countries in Africa, the Atlas hydrogeology map is the only available digital hydrogeology map.  
+
These maps are likely to be useful to people interested in groundwater resources, hydrogeology or geology of any of the relevant African countries. They provide a national overview of the groundwater resources of each country. For some countries in Africa, the Atlas hydrogeology map is the only available digital hydrogeology map.  
  
====Limitations of the Atlas country hydrogeology maps====
+
===Map Scale===
 +
 
 +
The maps provide a national-scale overview for each country, at a nominal scale of 1:5 million. This means that 1 cm on the maps is equivalent to 50 km on the ground. This makes them suitable for viewing at the following maximum sizes:
  
The large scale of the original map (1:5 million scale) means that the maps provide a country-scale overview - they do not show local scale detail. These maps are not based on field mapping and they have not been ground truthed. They may be different from other available hydrogeology maps.
+
* A2 – for the largest countries in Africa, such as Algeria and the Democratic Republic of Congo
 +
* A3 – for countries of a size similar to Sudan and Mali
 +
* A4 – for countries of a size similar to Kenya and Zambia
 +
* A5 – for countries of a size similar to Ghana and Tunisia
 +
* A6 – for the smallest countries in Africa, such as Burundi and Lesotho.  
  
Like all maps, these country hydrogeology maps are a two-dimensional representation of the complex three-dimensional hydrogeological reality. In most cases, these maps show the uppermost aquifer only. If there are other aquifers at depth, these are not shown. In some cases, where a major aquifer is overlain by relatively low permeability unconsolidated sediments (that don't form an important aquifer), the overlying unconsolidated sediments are not shown on the map.  
+
The maps are not suitable for providing detailed information on geology and hydrogeology at a sub-national (e.g. catchment) scale.
  
 
===Geology===
 
===Geology===
  
The Atlas geology maps show the geology of each country at a 1:5 million scale. Their main aim is to show key geological differences that are relevant to aquifer characteristics and hydrogeology. The geological classifications are broadly lithostratigraphical (based on the age and lithology (type) of the rocks), but geological units with similar aquifer (hydrogeological) characteristics may be grouped together in the Atlas maps, whereas in other geological maps they are separated. However, where possible, the geological unit names used in the maps are those used in the relevant country.  
+
The Atlas geology maps show the geology of each country at a 1:5 million scale. The geological descriptions reflect significant hydrogeological units at a national scale for each country, and where possible reflect geological nomenclature used (at this scale) in each country. The geological classifications are broadly lithostratigraphical (based on the age and lithology (type) of the rocks), and the geological descriptions can include some or all of: geological age; lithological description; and whether sediment is consolidated or unconsolidated. Because of the focus on hydrogeology, geological units with similar aquifer (hydrogeological) characteristics may be grouped together in the Atlas maps, whereas in other geological maps they are separated.  
 +
 
 +
For some countries an additional geology map has been developed that shows where extensive unconsolidated sediments overlie bedrock. At the moment, this is only available for Botswana, Mauritania and Sudan. Some other countries in Africa also have extensive covers of unconsolidated sediments, but at present this has not been shown separately, primarily because of: the complexity of displaying three dimensional geology on a two dimensional map; the availability of geological information and understanding; and the need to adapt each country map to reflect national approaches to geological categorisation.
  
 
===Hydrogeology===
 
===Hydrogeology===
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*'''aquifer type''' (based on the hydrogeological environment and the aquifer flow/storage type); and
 
*'''aquifer type''' (based on the hydrogeological environment and the aquifer flow/storage type); and
 
*'''aquifer productivity''' (relative aquifer productivity, or groundwater potential).  
 
*'''aquifer productivity''' (relative aquifer productivity, or groundwater potential).  
 +
 +
The combination of aquifer type and aquifer productivity to classify the hydrogeology of each country provides a practical description that will be understood by hydrogeologists. Definitions of aquifer type and aquifer productivity are given below.
  
 
====Aquifer Type====
 
====Aquifer Type====
  
Aquifer type is defined by combining the hydrogeological environment (the basic rock type) with the dominant method of groundwater flow and storage in the aquifer.  
+
Aquifer type is defined in terms of the hydrogeological environment, or the geological characteristics that largely control the nature of groundwater flow and storage in the aquifer. Each aquifer is defined as belonging to one of four main [[ Overview of Groundwater in Africa | '''hydrogeological environments''']] seen across Africa, with subdivisions of some of the categories (see table, below). These are a useful way of classifying aquifers, as each group has typical aquifer characteristics, and groundwater in each group behaves in similar ways.  
  
Each aquifer is defined as belonging to one of four main [[ Overview of Groundwater in Africa | '''hydrogeological environments''']] seen across Africa, listed below. These are a useful way of classifying aquifers, as each group has typical aquifer characteristics, and groundwater in each group behaves more or less in similar ways.  
+
The key feature of the aquifer type classification is the dominant way that groundwater flows through, and is stored in, aquifers: e.g. in weathered zones; as intergranular (or matrix) flows through pores; or through fractures; or through karstic (solution-enhanced) features.
  
 
{| class = "wikitable"
 
{| class = "wikitable"
|+ Hydrogeological Environment
+
|+Hydrogeological Environment
|Hydrogeological Environment||Summary
+
|Hydrogeological Environment||Subcategory||Summary||Main aquifer groups
 +
|-
 +
!colspan="4"|Unconsolidated
 +
|-
 +
|
 +
||Unconsolidated sedimentary aquifers with dominantly intergranular flow. Mostly Quaternary but also include some Tertiary age sediments. They are highly variable in their distribution, thickness, geometry and lithology, and therefore in their hydrogeological characteristics. The hydrogeology map shows some of the most hydrogeologically significant outcrops of unconsolidated deposits in Africa, particularly where these overlie lower productivity bedrock aquifers. However, it does not show all unconsolidated deposits. Particularly, over some of the major consolidated sedimentary basins, unconsolidated deposits of hydrogeological significance are not always shown, because the underlying consolidated sedimentary rocks form more productive and significant aquifers.
 +
||Aeolian (dune) sands, alluvium, coastal and marine sands and gravels.
 
|-
 
|-
|Basement aquifers
+
!colspan="4"|Consolidated sedimentary
||Crystalline basement rocks (metamorphic and igneous) most of which are Precambrian in age. These rocks develop distinctive local weathered (also called regolith) and fractured aquifers.
 
 
|-
 
|-
|Igneous aquifers (mostly volcanic)
+
|Consolidated Sedimentary Fracture
||Mostly volcanic aquifers, but in some areas also including intrusive igneous rocks, such as granites, that are younger than the Precambrian. These form fractured, weathered aquifers that are often strongly controlled by the geometry and weathering of former lava flows.
+
||Aquifers with dominantly fracture flow
 +
||Predominantly fracture flow and storage, with insignificant intergranular permeability and porosity (average porosity is < 0.1).
 +
||Volcanic and intrusive igneous rocks (although minor intergranular flow can occur in weathered zones in these rocks).
 +
|Consolidated Sedimentary Intergranular
 +
||Aquifers with dominantly intergranular flow
 +
||Intergranular storage is highly significant. Rock porosity is generally >0.25. Intergranular flow is dominant.
 +
||Younger consolidated sedimentary rocks (e.g. Cenozoic and younger Mesozoic in age), which tend to be loosely consolidated with significant intergranular permeability.
 +
|Consolidated Sedimentary Intergranular/Fracture
 +
||Aquifers with significant intergranular and fracture flow
 +
||Significant intergranular storage, with mixed intergranular and fracture flow. The average porosity of rocks is approximately 0.1 – 0.25.
 +
||Older sedimentary rocks (e.g. older Mesozoic and Palaeozoic), which tend to be well consolidated with low intergrangular permeability.
 +
|Consolidated Sedimentary Karst (sometimes also Consolidated Sedimentary Fracture Karst or Consolidated Sedimentary Intergranular Fracture Karst)
 +
||Aquifers with significant karstic features (sometimes also with significant intergranular and/or fracture flow)
 +
||A special case in karst aquifers. Predominantly fracture flow and storage.
 +
||Calcareous (limestone and dolomite) aquifers in which karstic features have developed.  
 
|-
 
|-
|Consolidated sedimentary aquifers
+
!colspan="4"|Igneous
||Consolidated (solid) sedimentary rocks. These are usually from Tertiary to Cambrian in age, but also include some older Precambrian sedimentary rocks that have not been highly metamorphosed. They have been subdivided according to the dominant groundwater flow and storage type (see below for more detail) – fracture, intergranular, or a combination of fracture and intergranular.
 
 
|-
 
|-
|Unconsolidated sedimentary aquifers
+
|Igneous Intrusive
||Mostly Quaternary but also include some Tertiary age sediments. They are highly variable in their distribution, thickness, geometry and lithology, and therefore in their hydrogeological characteristics. The hydrogeology map shows some of the most hydrogeologically significant outcrops of unconsolidated deposits in Africa, particularly where these overlie lower productivity bedrock aquifers. However, it does not show all unconsolidated deposits. Particularly, over some of the major consolidated sedimentary basins, unconsolidated deposits of hydrogeological significance are not always shown, because the underlying consolidated sedimentary rocks form more productive and significant aquifers.
+
||Intrusive igneous aquifers, often granitic, younger than Precambrian.
 +
|Volcanic
 +
||Volcanic fractured, weathered aquifers that are often strongly controlled by the geometry and weathering of former lava flows.
 +
||
 +
|-
 +
!colspan="4"|Basement
 +
|-
 +
|
 +
||Crystalline basement aquifers with typical weathered/fractured aquifer properties
 +
||All crystalline basement rocks belong to this category - i.e., most Precambrian rocks, with the exception of metasedimentary rocks that show little deformation.
 
|}
 
|}
 +
  
 
[[File:Africa_Hgcl_Envs.png|thumb| 400px|center| The main hydrogeological environments in Africa]]
 
[[File:Africa_Hgcl_Envs.png|thumb| 400px|center| The main hydrogeological environments in Africa]]
  
  
'''Aquifer flow/storage type''': the way that groundwater flows through aquifers, and is stored, is a key hydrogeological characteristic, and is a fundamental part of the classifications used in the Atlas hydrogeology maps. The maps use a semi-quantitative assessment of aquifer flow and storage type, based on geology and inferred porosity (MacDonald et al., 2010). The main distinction is whether groundwater is stored in, and flows through, '''fractures''' in a consolidated rock, or via '''intergranular''' flow in a porous rock or sediment matrix.
 
  
 
{| class = "wikitable"
 
{| class = "wikitable"
Line 129: Line 166:
  
 
Where possible, the maps have been validated in collaboration with hydrogeologists from the relevant countries who are co-authors on the relevant country pages of the Africa Groundwater Atlas (co-authors are referenced on the relevant Atlas country page and on this page http://earthwise.bgs.ac.uk/index.php/List_of_Authors).
 
Where possible, the maps have been validated in collaboration with hydrogeologists from the relevant countries who are co-authors on the relevant country pages of the Africa Groundwater Atlas (co-authors are referenced on the relevant Atlas country page and on this page http://earthwise.bgs.ac.uk/index.php/List_of_Authors).
 +
 +
====Limitations of the Atlas country hydrogeology maps====
 +
 +
The Atlas country hydrogeology maps provide a national (country) scale overview of the hydrogeology and geology. They are not suitable for providing detailed information on geology and hydrogeology at a sub-national (e.g. catchment) scale. They are suitable for viewing at sizes from A2 down to A6, depending on the size of the country (see the section Map Scale, above).
 +
 +
Like all maps, the country hydrogeology maps are a two-dimensional representation of the complex three-dimensional hydrogeological reality. In most cases, the maps show the uppermost aquifer only. If there are other aquifers at depth, these are not shown. In some cases, where a major aquifer is overlain by relatively low permeability unconsolidated sediments (that don't form an important aquifer), the overlying unconsolidated sediments are not shown on the map.
 +
 +
The maps reflect the current understanding of national geology and hydrogeology, given the scale of the geological base map linework and availability of geological and hydrogeological information. 
 +
 +
Because the maps reflect hydrogeological and geological terminology used in individual countries, the names and descriptions of hydrogeological or geological units that cross country (national) borders may not agree on both sides of the border (resulting in some country border ‘edges’ that have different colours/attribution).
 +
 +
The maps do not necessarily show the same information as other hydrogeology or geology maps available for any country.
  
 
==More Information==
 
==More Information==

Revision as of 10:19, 13 March 2019

Africa Groundwater Atlas >> Resource pages >> Africa Groundwater Atlas country hydrogeology maps

  This page is being revised. Please check back soon for updates
  

The Africa Groundwater Atlas Country Hydrogeology Maps

The country hydrogeology maps in this Atlas provide an overview of the hydrogeology and geology of each of 48 countries in Africa, at 1:5 million scale. The maps will be available to download as digital, GIS-enabled shapefiles with two themes:

  • geology, with geological categories that reflect significant hydrogeological units (MacDonald et al. 2010); and
  • hydrogeology, with categories that combine aquifer type and aquifer productivity.

More detail on these classifications is below.

Who might use the Atlas country hydrogeology maps

These maps are likely to be useful to people interested in groundwater resources, hydrogeology or geology of any of the relevant African countries. They provide a national overview of the groundwater resources of each country. For some countries in Africa, the Atlas hydrogeology map is the only available digital hydrogeology map.

Map Scale

The maps provide a national-scale overview for each country, at a nominal scale of 1:5 million. This means that 1 cm on the maps is equivalent to 50 km on the ground. This makes them suitable for viewing at the following maximum sizes:

  • A2 – for the largest countries in Africa, such as Algeria and the Democratic Republic of Congo
  • A3 – for countries of a size similar to Sudan and Mali
  • A4 – for countries of a size similar to Kenya and Zambia
  • A5 – for countries of a size similar to Ghana and Tunisia
  • A6 – for the smallest countries in Africa, such as Burundi and Lesotho.

The maps are not suitable for providing detailed information on geology and hydrogeology at a sub-national (e.g. catchment) scale.

Geology

The Atlas geology maps show the geology of each country at a 1:5 million scale. The geological descriptions reflect significant hydrogeological units at a national scale for each country, and where possible reflect geological nomenclature used (at this scale) in each country. The geological classifications are broadly lithostratigraphical (based on the age and lithology (type) of the rocks), and the geological descriptions can include some or all of: geological age; lithological description; and whether sediment is consolidated or unconsolidated. Because of the focus on hydrogeology, geological units with similar aquifer (hydrogeological) characteristics may be grouped together in the Atlas maps, whereas in other geological maps they are separated.

For some countries an additional geology map has been developed that shows where extensive unconsolidated sediments overlie bedrock. At the moment, this is only available for Botswana, Mauritania and Sudan. Some other countries in Africa also have extensive covers of unconsolidated sediments, but at present this has not been shown separately, primarily because of: the complexity of displaying three dimensional geology on a two dimensional map; the availability of geological information and understanding; and the need to adapt each country map to reflect national approaches to geological categorisation.

Hydrogeology

The hydrogeology maps show a combination of these two key hydrogeological parameters:

  • aquifer type (based on the hydrogeological environment and the aquifer flow/storage type); and
  • aquifer productivity (relative aquifer productivity, or groundwater potential).

The combination of aquifer type and aquifer productivity to classify the hydrogeology of each country provides a practical description that will be understood by hydrogeologists. Definitions of aquifer type and aquifer productivity are given below.

Aquifer Type

Aquifer type is defined in terms of the hydrogeological environment, or the geological characteristics that largely control the nature of groundwater flow and storage in the aquifer. Each aquifer is defined as belonging to one of four main hydrogeological environments seen across Africa, with subdivisions of some of the categories (see table, below). These are a useful way of classifying aquifers, as each group has typical aquifer characteristics, and groundwater in each group behaves in similar ways.

The key feature of the aquifer type classification is the dominant way that groundwater flows through, and is stored in, aquifers: e.g. in weathered zones; as intergranular (or matrix) flows through pores; or through fractures; or through karstic (solution-enhanced) features.

Hydrogeological Environment
Hydrogeological Environment Subcategory Summary Main aquifer groups
Unconsolidated
Unconsolidated sedimentary aquifers with dominantly intergranular flow. Mostly Quaternary but also include some Tertiary age sediments. They are highly variable in their distribution, thickness, geometry and lithology, and therefore in their hydrogeological characteristics. The hydrogeology map shows some of the most hydrogeologically significant outcrops of unconsolidated deposits in Africa, particularly where these overlie lower productivity bedrock aquifers. However, it does not show all unconsolidated deposits. Particularly, over some of the major consolidated sedimentary basins, unconsolidated deposits of hydrogeological significance are not always shown, because the underlying consolidated sedimentary rocks form more productive and significant aquifers. Aeolian (dune) sands, alluvium, coastal and marine sands and gravels.
Consolidated sedimentary
Consolidated Sedimentary Fracture Aquifers with dominantly fracture flow Predominantly fracture flow and storage, with insignificant intergranular permeability and porosity (average porosity is < 0.1). Volcanic and intrusive igneous rocks (although minor intergranular flow can occur in weathered zones in these rocks). Consolidated Sedimentary Intergranular Aquifers with dominantly intergranular flow Intergranular storage is highly significant. Rock porosity is generally >0.25. Intergranular flow is dominant. Younger consolidated sedimentary rocks (e.g. Cenozoic and younger Mesozoic in age), which tend to be loosely consolidated with significant intergranular permeability. Consolidated Sedimentary Intergranular/Fracture Aquifers with significant intergranular and fracture flow Significant intergranular storage, with mixed intergranular and fracture flow. The average porosity of rocks is approximately 0.1 – 0.25. Older sedimentary rocks (e.g. older Mesozoic and Palaeozoic), which tend to be well consolidated with low intergrangular permeability. Consolidated Sedimentary Karst (sometimes also Consolidated Sedimentary Fracture Karst or Consolidated Sedimentary Intergranular Fracture Karst) Aquifers with significant karstic features (sometimes also with significant intergranular and/or fracture flow) A special case in karst aquifers. Predominantly fracture flow and storage. Calcareous (limestone and dolomite) aquifers in which karstic features have developed.
Igneous
Igneous Intrusive Intrusive igneous aquifers, often granitic, younger than Precambrian. Volcanic Volcanic fractured, weathered aquifers that are often strongly controlled by the geometry and weathering of former lava flows.
Basement
Crystalline basement aquifers with typical weathered/fractured aquifer properties All crystalline basement rocks belong to this category - i.e., most Precambrian rocks, with the exception of metasedimentary rocks that show little deformation.


The main hydrogeological environments in Africa


Aquifer flow and storage type
Aquifer flow/storage type Summary Main aquifer groups
Intergranular Intergranular storage is highly significant. Rock porosity is generally >0.25. Intergranular flow is dominant. Unconsolidated sedimentary aquifers, and younger consolidated sedimentary rocks (e.g. Cenozoic and younger Mesozoic in age), which tend to be loosely consolidated with significant intergranular permeability.
Intergranular and fracture Significant intergranular storage, with mixed intergranular and fracture flow. The average porosity of rocks is approximately 0.1 – 0.25. Older sedimentary rocks (e.g. older Mesozoic and Palaeozoic), which tend to be well consolidated with low intergrangular permeability.
Fracture Predominantly fracture flow and storage, with insignificant intergranular permeability and porosity (average porosity is < 0.1). Volcanic and intrusive igneous rocks (although minor intergranular flow can occur in weathered zones in these rocks).
Fracture (karst) A special case in karst aquifers. Predominantly fracture flow and storage. Calcareous (limestone and dolomite) aquifers in which karstic features have developed.
Fracture (weathered) A special case in basement aquifers. Significant fracture flow in unweathered parts of very low porosity (<0.01) rocks, with some intergranular flow and storage in weathered zones. All crystalline basement rocks belong to this category - i.e., most Precambrian rocks, with the exception of metasedimentary rocks that show little deformation.
Aquifer flow and storage type across Africa

Aquifer productivity

Borehole yield is used as a proxy for aquifer productivity in the Atlas country hydrogeology maps. Estimation of typical boreholes yields in the main aquifer types was based on an analysis of collated borehole yield data for aquifers across Africa.

Six main borehole yield classes are distinguished. These classes relate to the estimated average sustainable yield that could obtained from a single, effectively sited and developed borehole (MacDonald et al. 2010). The classes are described in terms of relative aquifer productivity, from Very Low to Very High (see table below). In some cases, combined classes are used to describe aquifers which are very heterogeneous and have a large range in observed yields, or where there isn't enough information to be confident about assigning only one class.

Aquifer productivity
Aquifer productivity Yield range (litres/second or l/s)
Very high > 20
High 5 - 20
Moderate 2 - 5
Low to moderate 0.5 - 2
Low 0.1 - 0.5
Very low < 0.1
Aquifer productivity across Africa


How the Atlas country hydrogeology maps were developed

The Atlas country hydrogeology maps were developed in ArcGIS by modifying and attributing a digital Africa-wide geology map at 1:5 million scale, using available hydrogeological and geological information.

The 1:5 million scale geology map was originally published by UNESCO (Furon and Lombard 1964), and was digitised by, and is made available through, the USGS (Persits et al., 2002). It can be accessed and downloaded in shapefile format via the USGS (details in References). The digitised geology map includes some linework defining coasts that was created using Esri© data, used with permission of Esri©.

The country maps are a further development of the Africa-wide quantitative groundwater maps that were produced by BGS in 2012 (MacDonald et al. 2012). The country maps use the hydrogeological understanding captured in the Africa-wide maps and incorporate additional geological and hydrogeological information from individual countries. They reflect the current understanding of national geology and hydrogeology, given the scale of the geological base map linework and availability of geological and hydrogeological information and, where possible, they reflect different national approaches to geological and hydrogeological categorisation.

Where possible, the maps have been validated in collaboration with hydrogeologists from the relevant countries who are co-authors on the relevant country pages of the Africa Groundwater Atlas (co-authors are referenced on the relevant Atlas country page and on this page http://earthwise.bgs.ac.uk/index.php/List_of_Authors).

Limitations of the Atlas country hydrogeology maps

The Atlas country hydrogeology maps provide a national (country) scale overview of the hydrogeology and geology. They are not suitable for providing detailed information on geology and hydrogeology at a sub-national (e.g. catchment) scale. They are suitable for viewing at sizes from A2 down to A6, depending on the size of the country (see the section Map Scale, above).

Like all maps, the country hydrogeology maps are a two-dimensional representation of the complex three-dimensional hydrogeological reality. In most cases, the maps show the uppermost aquifer only. If there are other aquifers at depth, these are not shown. In some cases, where a major aquifer is overlain by relatively low permeability unconsolidated sediments (that don't form an important aquifer), the overlying unconsolidated sediments are not shown on the map.

The maps reflect the current understanding of national geology and hydrogeology, given the scale of the geological base map linework and availability of geological and hydrogeological information.

Because the maps reflect hydrogeological and geological terminology used in individual countries, the names and descriptions of hydrogeological or geological units that cross country (national) borders may not agree on both sides of the border (resulting in some country border ‘edges’ that have different colours/attribution).

The maps do not necessarily show the same information as other hydrogeology or geology maps available for any country.

More Information

MacDonald AM, and Davies J. 2000. A brief review of groundwater for rural water supply in sub-Saharan Africa. British Geological Survey Technical Report, WC/00/033, 30pp.

MacDonald AM, Bonsor HC, Ó Dochartaigh BÉ and Taylor RG. 2012. Quantitative maps of groundwater resources in Africa. Environmental Research Letters, Vol. 7(2). http://nora.nerc.ac.uk/17892/ doi:10.1088/1748-9326/7/2/024009

MacDonald AM, Ó Dochartaigh BÉ, Bonsor HC, Davies J, and Key R. 2010. Developing quantitative aquifer maps for Africa. British Geological Survey Internal Report, IR/10/103.

See also the Quantitative groundwater maps for Africa project webpage.


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