Editing Urban groundwater in Africa

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[[Africa Groundwater Atlas Home | Africa Groundwater Atlas]] >> [[Additional resources | Resource pages]] >> Urban groundwater in Africa
 
[[Africa Groundwater Atlas Home | Africa Groundwater Atlas]] >> [[Additional resources | Resource pages]] >> Urban groundwater in Africa
 
  Please cite page as: Africa Groundwater Atlas. 2019. Urban groundwater in Africa. British Geological Survey. Accessed [date you accessed the information]. ''Weblink''.
 
  
 
   '''This page is being developed. Please check back soon for more content.'''
 
   '''This page is being developed. Please check back soon for more content.'''
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Shallower groundwater is at higher risk of pollution than deeper groundwater, because the travel times for pollutants to shallow groundwater are much shorter. Because of this, groundwater from shallow sources, such as hand-dug wells, is more at risk. However, deeper groundwater can also be at risk, depending on the type and amount of pollution and the local hydrogeological conditions, and so even well-constructed deep municipal or private boreholes can be affected.  
 
Shallower groundwater is at higher risk of pollution than deeper groundwater, because the travel times for pollutants to shallow groundwater are much shorter. Because of this, groundwater from shallow sources, such as hand-dug wells, is more at risk. However, deeper groundwater can also be at risk, depending on the type and amount of pollution and the local hydrogeological conditions, and so even well-constructed deep municipal or private boreholes can be affected.  
  
The diagram below illustrates some of the key potential sources and pathways for faecal contaminants in groundwater in towns and cities in Africa. Many of these are similar for other groundwater contaminants.
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[[File:UrbanGWRisk.gif|thumb| 400px|center| Key potential sources, pathways and receptors of faecal contamination in groundwater in urban areas in Sub-Saharan Africa, from [http://nora.nerc.ac.uk/516133/ Lapworth et al. (2017)]]]  
 
 
[[File:UrbanGWRisk.gif|thumb| 500px|center| Key potential sources, pathways and receptors of faecal contamination in groundwater in urban areas in Sub-Saharan Africa, from [http://nora.nerc.ac.uk/516133/ Lapworth et al. (2017)]]]  
 
 
   
 
   
 
Many pollutants can affect groundwater in urban areas. including microbiological and chemical. Microbiological contamination from faecal waste is the largest source of contamination in urban (and rural) groundwater in Africa. Chemical pollutants include heavy metals and health-impacting chemicals such as cyanide, arsenic and chromium from industry and other municipal sources; pesticides and nutrients such as nitrate and phosphate from urban agriculture as well as domestic sources.  
 
Many pollutants can affect groundwater in urban areas. including microbiological and chemical. Microbiological contamination from faecal waste is the largest source of contamination in urban (and rural) groundwater in Africa. Chemical pollutants include heavy metals and health-impacting chemicals such as cyanide, arsenic and chromium from industry and other municipal sources; pesticides and nutrients such as nitrate and phosphate from urban agriculture as well as domestic sources.  
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===Over-abstraction of groundwater===
 
===Over-abstraction of groundwater===
  
As urbanisation continues, the demand for water is increasing in urban areas. This demand is being partially met by municipal piped water supplies. Where urban areas have easy access to highly productive aquifers, municipal supplies may be at least partially sourced from groundwater within or near urban boundaries. If municipal abstraction is greater than recharge, it this can lead to localised falling groundwater levels.
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As urbanisation continues, the demand for water is increasing in urban areas. This demand is being only partially met by municipal piped water supplies. Where urban areas have easy access to highly productive aquifers, municipal supplies can be at least partially sourced from groundwater. If municipal pumping is greater than recharge, it this can lead to localised falling groundwater levels
  
Because in most towns and cities in Africa, municipal piped water supplies aren't keeping pace with demand, more and more urban residents are turning to 'self supply' from groundwater sources. This involves digging or drilling private domestic wells or boreholes. Urban community water supplies may also be sourced from boreholes or wells. These boreholes and wells tend to be shallow. As well as being vulnerable to contamination, such shallow aquifers can also be vulnerable to over-abstraction, if too much groundwater is pumped out. The result can be serious localised aquifer depletion, which may lead to boreholes and wells drying up if groundwater levels fall too far; and also brings risks of inducing seepage of contaminated water, or saline intrusion in coastal areas; and can also cause land subsidence (Foster 2018).  
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Because in most towns and cities in Africa, municipal piped water supplies aren't keeping pace with demand, more and more urban residents are turning to 'self supply' from groundwater sources. This involves digging or drilling private domestic wells or boreholes. Urban community water supplies may also be sourced from boreholes or wells.  
  
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There are rarely sufficient groundwater resources within urban areas themselves to satisfy
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water-demand in larger cities, and resource sustainability has often become an issue. Serious localised aquifer
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depletion (especially in semi-confined aquifer systems) results, with risk of induced seepage of contaminated
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water, land subsidence or coastal saline intrusion
  
 
==Overviews of urban groundwater in Africa==
 
==Overviews of urban groundwater in Africa==

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