Difference between revisions of "Aquifer properties"

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[[Africa Groundwater Atlas Home | Africa Groundwater Atlas]] >> [[Additional resources | Additional resources]] >> Aquifer Properties
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[[Africa Groundwater Atlas Home | Africa Groundwater Atlas]] >> [[Additional resources | Resource pages]] >> Aquifer Properties
  
[[File: Hydrogeology.png | 500px]] [[File: Hydrogeology_Key.png | 500x195px]]
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Please cite page as: Africa Groundwater Atlas. 2019. Aquifer properties. British Geological Survey. Accessed [date you accessed the information]. ''Weblink''.
  
== Dataset Description ==
 
  
The hydrogeology map shown here was developed by the British Geological Survey as part of a series of continent-scale quantitative groundwater maps showing aquifer productivity, saturated aquifer thickness, and aquifer flow and  storage type, which were presented by MacDonald et al. (2010; 2012). This new hydrogeology map combines geology, aquifer productivity, and aquifer flow/storage type. It provides a geologically based view of the overall hydrogeological environment, reflecting the overall control that the geological environment has on the presence and movement of groundwater in aquifers, and indicates the relative aquifer productivity, from very high to very low. It should be remembered that like all maps, this is a two-dimensional representation of the complex three-dimensional geological reality. The map shows the following aquifer groups:
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  This page is still in development. Please check back soon for updates.
  
*Basement aquifers, incorporating all Precambrian crystalline basement complex rocks. These develop distinctive, often local, weathered (also called regolith) and fractured aquifers.
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==Aquifer properties==
*Igneous aquifers, including both volcanic and intrusive rocks (such as granites). Across much of Africa, most large outcrops of igneous rocks shown on this map are volcanic. These form fractured, weathered aquifers that are often strongly controlled by the geometry and weathering of former lava flows.
 
*Consolidated sedimentary aquifers, which have been subdivided according to the dominant groundwater flow type – fracture, intergranular, or a combination of fracture and intergranular.
 
*Unconsolidated sedimentary aquifers. These are very 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.
 
  
The hydrogeology map is based on a 1:5,000,000 (5 million) scale geology map [[Geology|described here]], which was attributed with quantitative and qualitative hydrogeological information derived from published hydrogeological maps and studies of aquifer properties.  
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Aquifer properties are the hydraulic characteristics of aquifers, which are used to describe an aquifer and understand how groundwater in the aquifer exists and behaves. Aquifer properties are the most important way to describe the hydrogeology of an aquifer.  
  
This continent-scale map was used as the basis of new country-scale hydrogeology maps for each country in Africa, which are presented in this Atlas. Because the map is based on 1:5 million scale linework, it is not always appropriate or accurate at the scale of individual countries. Where this is the case, the country maps have, wherever possible, been updated in collaboration with experts in the country's hydrogeology, to better reflect the geology at a country scale.  
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Key aquifer properties are '''permeability''' (or '''transmissivity'''); '''storage'''; and '''thickness'''.  
  
IMAGES OF AFRICA MAPS
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To get reliable information on aquifer properties, aquifer testing must be carried out. Drilling and carrying out controlled '''test pumping''' of boreholes allows estimates of aquifer thickness, permeability, transmissivity and storage to be made. Without controlled test pumping, it is not possible to accurately estimate these aquifer properties.
  
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In many parts of Africa, quantitative aquifer properties data are scarce, and surrogate data and information must be used instead in order to characterise aquifers. The most commonly available hydrogeological data are geology; borehole depth; and borehole yield. Geological and borehole yield data have been used to develop the [[Hydrogeology Map | hydrogeology map]] used in this Atlas.
  
;Citations and links:
 
  
:MacDonald AM, Bonsor HC, Ó Dochartaigh BE and Taylor RG. 2012 Quantitative maps of groundwater resources in Africa. Environmental Research Letters, 7 (2), 024009. 10.1088/1748-9326/7/2/024009
 
  
:MacDonald AM, Ó Dochartaigh BE, Bonsor HC, Davies J and Key R. 2010 Developing quantitative aquifer maps for Africa. Nottingham, UK, British Geological Survey Internal Report IR/10/103. http://nora.nerc.ac.uk/501779/ 
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Return to: [[Africa Groundwater Atlas Home | Africa Groundwater Atlas]] >> [[Additional resources | Resource pages]] >> Aquifer Properties
 
 
 
 
== Further Sources of Information ==
 
The World-wide Hydrogeological Mapping and Assessment Programme (WHYMAP) was launched in 2000 to provide data and information about global groundwater resources. Several global and continental scale maps related to groundwater resources, groundwater basins, large aquifer systems, and transboundary aquifers are available to download from the [http://www.whymap.org/whymap/EN/Downloads/downloads_node_en.html WHYMAP website].
 
 
 
 
 
 
 
[[Africa Groundwater Atlas Home | Africa Groundwater Atlas]] >> [[Additional resources | Additional resources]] >> Aquifer properties
 
  
  
 
[[Category:Additional resources]]
 
[[Category:Additional resources]]
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[[Category:Africa Groundwater Atlas]]

Latest revision as of 11:03, 2 July 2019

Africa Groundwater Atlas >> Resource pages >> Aquifer Properties

Please cite page as: Africa Groundwater Atlas. 2019. Aquifer properties. British Geological Survey. Accessed [date you accessed the information]. Weblink.


  This page is still in development. Please check back soon for updates.

Aquifer properties

Aquifer properties are the hydraulic characteristics of aquifers, which are used to describe an aquifer and understand how groundwater in the aquifer exists and behaves. Aquifer properties are the most important way to describe the hydrogeology of an aquifer.

Key aquifer properties are permeability (or transmissivity); storage; and thickness.

To get reliable information on aquifer properties, aquifer testing must be carried out. Drilling and carrying out controlled test pumping of boreholes allows estimates of aquifer thickness, permeability, transmissivity and storage to be made. Without controlled test pumping, it is not possible to accurately estimate these aquifer properties.

In many parts of Africa, quantitative aquifer properties data are scarce, and surrogate data and information must be used instead in order to characterise aquifers. The most commonly available hydrogeological data are geology; borehole depth; and borehole yield. Geological and borehole yield data have been used to develop the hydrogeology map used in this Atlas.


Return to: Africa Groundwater Atlas >> Resource pages >> Aquifer Properties