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[[Africa Groundwater Atlas Home | Africa Groundwater Atlas]] >> [[Hydrogeology by country | Hydrogeology by country]] >> Hydrogeology of the Gambia
 
 
[[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]]]
 
 
The Republic of the Gambia is the smallest mainland African country. By the 14th century, most of what is now Gambia was part of the Mali empire. From the 15th century, many European powers established trading posts in the Senegambia area, which included the Malinke and Wolof kingdoms and was also inhabited by the pastoral nomadic Fulani who are found throughout West Africa. Portuguese traders were followed by colonial rule from first Britain, then France, then Britain again from the late 16th century. The Gambia won independence in 1965, and saw relatively stable government until an attempted coup in 1981, in the aftermath of which the Gambia and Senegal formed the Senegambia Confederation in 1982. The Gambia withdrew from the confederation in 1989. Another military uprising in 1994 saw the first change in president since independence, with a full return to democratic elections in 2001. The second president was ousted in elections in 2017. Gambia left the Commonwealth in 2013 and applied to return in 2018.
 
 
The Arab and then transatlantic slave trades were dominant economic activities from the 10th to the 19th centuries. Today, agriculture accounts for around 30% of GDP and employs about 70% of the labour force, with groundnuts for export a particularly important crop, although rice has been promoted in an attempt to diversify the agricultural economy. Manufacturing is largely based on agriculture, including groundnut processing. The port of Banjul is important in the export and re-export of agricultural products. Services, particularly tourism, account for about 60% of GDP: the tourism sector is largely built around the ecology and wildlife of the Gambia River floodplain.
 
 
The Gambia has plentiful surface water in the Gambia River, but this is rarely used for potable water supply because of poor water quality: the highest water demand, in population centres and tourism facilities, is in the coastal areas, where the river has high salinity. Highly seasonal rainfall and a lack of smaller perennial rivers away mean that most potable water demand, in rural and urban areas, is met by groundwater.
 
 
 
 
==Authors==
 
==Authors==
  
 
'''Landing Bojang''', Department of Water Resources, The Gambia
 
'''Landing Bojang''', Department of Water Resources, The Gambia
  
'''Giran Corr''', RC Engineering / NIRAS, The Gambia
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'''Kirsty Upton''' & '''Brighid Ó Dochartaigh''', British Geological Survey, UK
 
 
'''Dr Kirsty Upton''', '''Brighid Ó Dochartaigh''', British Geological Survey, UK
 
 
 
'''Dr Imogen Bellwood-Howard''', Institute of Development Studies, UK
 
 
 
 
 
Please cite this page as: Bojang, Corr, Upton, Ó Dochartaigh and Bellwood-Howard, 2018.
 
  
Bibliographic reference: Bojang L, Corr G, Upton K, Ó Dochartaigh BÉ and Bellwood-Howard, I. 2018. Africa Groundwater Atlas: Hydrogeology of the Gambia. British Geological Survey. Accessed [date you accessed the information]. http://earthwise.bgs.ac.uk/index.php/Hydrogeology_of_Gambria
 
  
==Terms and conditions==
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==Geographical and Political Setting==
  
The Africa Groundwater Atlas is hosted by the British Geological Survey (BGS) and includes information from third party sources. Your use of information provided by this website is at your own risk. If reproducing diagrams that include third party information, please cite both the Africa Groundwater Atlas and the third party sources. Please see the [[Africa Groundwater Atlas Terms of Use | Terms of use]] for more information.
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Gambia is the smallest country in Africa. It borders the Atlantic Ocean to the west, and is otherwise entirely surrounded by the country of Senegal. The majority the country comprises the floodplain of the Gambia River, which originates in Guinea before flowing through Senegal and through Gambia to the sea. The country is therefore generally very flat, ranging from 0 to <100 m above sea level.
  
==Geographical Setting==
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[[File:Gambia_Political.png | right | frame | Political Map of Gambia (For more information on the datasets used in the map see the [[Geography | geography resources section]])]]
  
 
===General===
 
===General===
 
The Gambia is the smallest country in Africa. It borders the Atlantic Ocean to the west, and is otherwise entirely surrounded by the country of Senegal. The majority the country comprises the floodplain of the Gambia River, which originates in Guinea before flowing through Senegal and through the Gambia to the sea. The country is therefore generally very flat, ranging from 0 to <100 m above sea level.
 
 
[[File:Gambia_Political.png | right | frame | The Gambia. Map developed from USGS GTOPOPO30; GADM global administrative areas; and UN Revision of World Urbanization Prospects. For more information on the map development and datasets see the [[Geography | geography resource page]])]]
 
  
  
 
{| class = "wikitable"
 
{| class = "wikitable"
 
|-
 
|-
|Capital city || Banjul
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|Estimated Population in 2013* || 1,849,285
 
|-
 
|-
|Region || West Africa
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|Rural Population (% of total)* || 42%
 
|-
 
|-
|Border countries || Senegal
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|Total Surface Area* || 10,120 sq km
 
|-
 
|-
|Total surface area* || 11,300 km<sup>2</sup>  ( 1,130,000 ha)
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|Agricultural Land (% of total area)* || 60%
 
|-
 
|-
|Total population (2015)* ||  
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|Capital City || Banjul
 
|-
 
|-
|Rural population (2015)* || 816,000 (41%)
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|Region || West Africa
 
|-
 
|-
|Urban population (2015)* || 1,175,000 (59%)
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|Border Countries || Senegal
 
|-
 
|-
|UN Human Development Index (HDI) [highest = 1] (2014)*|| 0.4406
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|Annual Freshwater Withdrawal (2013)* || 91 Million cubic metres
 +
|-
 +
|Annual Freshwater Withdrawal for Agriculture* || 43%
 +
|-
 +
|Annual Freshwater Withdrawal for Domestic Use* || 37%
 +
|-
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|Annual Freshwater Withdrawal for Industry* || 19%
 +
|-
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|Rural Population with Access to Improved Water Source* ||84%
 +
|-
 +
|Urban Population with Access to Improved Water Source* || 94%
 
|}
 
|}
  
<nowiki>*</nowiki> Source: [http://www.fao.org/nr/water/aquastat/data/query/index.html?lang=en FAO Aquastat]
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<nowiki>*</nowiki> Source: World Bank
 +
 
  
 +
===Climate===
  
 +
The climate of Gambia is largely classified as tropical savannah, apart from the central north region which transitions into hot, arid steppe. There is little spatial variation in average annual precipitation and temperature, other than a slight reduction in rainfall in the central north region.
  
===Climate===
 
  
The climate of the Gambia is largely classified as tropical savannah, apart from the central north region which transitions into hot, arid steppe. There is little spatial variation in average annual precipitation and temperature, other than a slight reduction in rainfall in the central north region.  
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<gallery widths="375px" heights=365px mode=nolines>
 +
File:Gambia_ClimateZones.png |Koppen Geiger Climate Zones
 +
File:Gambia_ClimatePrecip.png |Average Annual Precipitation
 +
File:Gambia_ClimateTemp.png |Average Temperature
 +
</gallery>
  
 
Gambia has a very distinct wet season between June and October, and is relatively dry from November to April. The wet season is relatively hot compared to the cooler dry season.
 
Gambia has a very distinct wet season between June and October, and is relatively dry from November to April. The wet season is relatively hot compared to the cooler dry season.
 
   
 
   
[[File:Gambia_ClimateZones.png | 375x365px |Koppen Geiger Climate Zones]][[File:Gambia_ClimatePrecip.png | 375x365px |Average Annual Precipitation]][[File:Gambia_ClimateTemp.png | 375x365px |Average Temperature]]
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Rainfall time-series and graphs of monthly average rainfall and temperature for the two climate zones in Gambia can be found on the [[Climate of Gambia | Gambia Climate Page]].
 +
 
 +
 
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[[File:Gambia_pre_Monthly.png| 255x124px| Average monthly precipitation for Gambia showing minimum and maximum (light blue), 25th and 75th percentile (blue), and median (dark blue) rainfall]] [[File:Gambia_tmp_Monthly.png| 255x124px| Average monthly temperature for Gambia showing minimum and maximum (orange), 25th and 75th percentile (red), and median (black) temperature]] [[File:Gambia_pre_Qts.png | 255x124px | Quarterly precipitation over the period 1950-2012]] [[File:Gambia_pre_Mts.png|255x124px | Monthly precipitation (blue) over the period 2000-2012 compared with the long term monthly average (red)]]  
 
   
 
   
[[File:Gambia_pre_Monthly.png| 255x124px| Average monthly precipitation for Gambia showing minimum and maximum (light blue), 25th and 75th percentile (blue), and median (dark blue) rainfall]] [[File:Gambia_tmp_Monthly.png| 255x124px| Average monthly temperature for Gambia showing minimum and maximum (orange), 25th and 75th percentile (red), and median (black) temperature]] [[File:Gambia_pre_Qts.png | 255x124px | Quarterly precipitation over the period 1950-2012]] [[File:Gambia_pre_Mts.png|255x124px | Monthly precipitation (blue) over the period 2000-2012 compared with the long term monthly average (red)]]
 
  
 +
For further detail on the climate datasets used see the [[Climate | climate resources section]].
  
More information on average rainfall and temperature for each climate zone in Gambia can be found on the [[Climate of Gambia | Gambia Climate Page]].
 
 
These maps and graphs were developed from the CRU TS 3.21 dataset produced by the Climatic Research Unit at the University of East Anglia, UK. For more information see the [[Climate | climate resource page]].
 
  
 
===Surface water===
 
===Surface water===
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{|
 
{|
 
|-
 
|-
|The Gambia is dominated by the perennial Gambia River, which has its source in Guinea and flows through Senegal before flowing along the entire length of the Gambia from the east to its discharge point to the Atlantic Ocean to the west. Its flow is highly seasonal, with maximum flows at the end of the rainy season in late September-October
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|Gambia is dominated by the perennial Gambia River, which flows along the entire length of the country from the border with Senegal in the east to its discharge point to the Atlantic Ocean to the west.
  
 
The Department of Water Resources is responsible for river flow gauging, and currently monitors the Gambia River close to its discharge point to the Atlantic Ocean.  
 
The Department of Water Resources is responsible for river flow gauging, and currently monitors the Gambia River close to its discharge point to the Atlantic Ocean.  
  
  
| [[File:Gambia_Hydrology.png | frame | Major surface water features of the Gambia. Map developed from World Wildlife Fund HydroSHEDS; Digital Chart of the World drainage; and FAO Inland Water Bodies. For more information on the map development and datasets see the [[Surface water | surface water resource page]]]]
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| [[File:Gambia_Hydrology.png | frame | Surface Water Map of Gambia (For more information on the datasets used in the map see the [[Surface water | surface water resources section]])]]
 
|}
 
|}
 +
  
 
===Soil===
 
===Soil===
 
{|
 
{|
 
|-
 
|-
| [[File:Gambia_soil.png | frame | Soil map of the Gambia, from the European Commission Joint Research Centre: European Soil Portal. For more information on the map see the [[Soil | soil resource page]]]]
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| [[File:Gambia_soil.png | frame | Soil Map of Gambia (For more information on the datasets used in the map see the [[Soil | soil resources section]])]]
  
 
|Soils across the floodplain of the Gambia River are dominantly Gleysols, which are highly important for agriculture.
 
|Soils across the floodplain of the Gambia River are dominantly Gleysols, which are highly important for agriculture.
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|
 
|
  
| [[File:Gambia_LandCover.png | frame | Land Cover Map of the Gambia, from the European Space Agency GlobCover 2.3, 2009. For more information on the map see the [[Land cover | land cover resource page]]]]
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| [[File:Gambia_LandCover.png | frame | Land Cover Map of Gambia (For more information on the datasets used in the map see the [[Land cover | land cover resources section]])]]
 
|}
 
|}
 
===Water statistics===
 
 
{| class = "wikitable"
 
| || 1999 ||2000||2005||2014||2015
 
|-
 
|Rural population with access to safe drinking water (%) || || ||  || || 84.4
 
|-
 
|Urban population with access to safe drinking water (%) || || ||  || || 94.2
 
|-
 
|Population affected by water related disease || No data || No data || No data || No data || No data
 
|-
 
|Total internal renewable water resources (cubic metres/inhabitant/year) || || ||  || 1,507||
 
|-
 
|Total exploitable water resources (Million cubic metres/year) || No data || No data || No data || No data || No data
 
|-
 
|Freshwater withdrawal as % of total renewable water resources || || 1.131|| || ||
 
|-
 
|Total renewable groundwater (Million cubic metres/year) ||  || || ||500 ||
 
|-
 
|Exploitable: Regular renewable groundwater (Million cubic metres/year) || No data || No data || No data || No data || No data
 
|-
 
|Groundwater produced internally (Million cubic metres/year) || || ||  ||500 ||
 
|-
 
|Fresh groundwater withdrawal (primary and secondary) (Million cubic metres/year) || No data || No data || No data || No data || No data
 
|-
 
|Groundwater: entering the country (total) (Million cubic metres/year) || No data || No data || No data || No data || No data
 
|-
 
|Groundwater: leaving the country to other countries (total) (Million cubic metres/year) || No data || No data || No data || No data || No data
 
|-
 
|Industrial water withdrawal (all water sources) (Million cubic metres/year) || || ||21.2 || ||
 
|-
 
| Municipal water withdrawal (all water sources) (Million cubic metres/year)  || || ||41.2 || ||
 
|-
 
|Agricultural water withdrawal (all water sources) (Million cubic metres/year) ||39.2 || || || ||
 
|-
 
|Irrigation water withdrawal (all water sources)<sup>1</sup> (Million cubic metres/year) ||39.2 || ||  || ||
 
|-
 
|Irrigation water requirement (all water sources)<sup>1</sup> (Million cubic metres/year) ||12 || ||  || ||
 
|-
 
|Area of permanent crops (ha) || || ||  ||5,000 ||
 
|-
 
|Cultivated land (arable and permanent crops) (ha) || || || ||445,000 ||
 
|-
 
|Total area of country cultivated (%) || || ||  ||39.38 ||
 
|-
 
|Area equipped for irrigation by groundwater (ha) ||15 || ||  || ||
 
|-
 
|Area equipped for irrigation by mixed surface water and groundwater (ha) || No data || No data || No data || No data || No data
 
|}
 
 
These statistics are sourced from [http://www.fao.org/nr/water/aquastat/main/index.stm FAO Aquastat]. They are the most recent available information in the Aquastat database. More information on the derivation and interpretation of these statistics can be seen on the FAO Aquastat website.
 
 
Further water and related statistics can be accessed at the [http://www.fao.org/nr/water/aquastat/data/query/index.html?lang=en Aquastat Main Database].
 
 
<sup>1</sup> More information on [http://www.fao.org/nr/water/aquastat/water_use_agr/index.stm irrigation water use and requirement statistics]
 
  
 
==Geology==
 
==Geology==
 
+
[[File: Gambia_Geology2.png ]]
This section provides a summary of the geology of the Gambia.
 
 
 
The geology map on this page shows a simplified version of the geology at a national scale (see the [[Geology | geology resource page]] for more details).
 
 
 
[https://www.bgs.ac.uk/africagroundwateratlas/downloadGIS.html '''Download a GIS shapefile of the Gambia geology and hydrogeology map'''].
 
 
 
[[File:Gambia_Geology3.png | center | thumb|500px | Geology of the Gambia 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]]. [https://www.bgs.ac.uk/africagroundwateratlas/downloadGIS.html Download a GIS shapefile of the Gambia geology and hydrogeology map].]]
 
 
 
  
 
{| class = "wikitable"
 
{| class = "wikitable"
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==Hydrogeology==
 
==Hydrogeology==
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There are two main aquifers in Gambia: the upper Quaternary unconsolidated sands comprise a shallow sand aquifer (SSA), which is an important aquifer throughout Gambia. The deeper Cretaceous sediments form a deep sandstone aquifer (DSA). More detail is in the Aquifer Properties section below.
  
This section provides a summary of the hydrogeology of the main aquifers in the Gambia.  More information is available in the references listed at the bottom of this page. Many of these references can be accessed through the [http://www.bgs.ac.uk/africagroundwateratlas/index.cfm Africa Groundwater Literature Archive].
 
  
The hydrogeology map on this page shows a simplified version 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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===Aquifer properties===
 
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[[File:Gambia_Hydrogeology.png]] [[File: Hydrogeology_Key.png | 500x195px]]
[https://www.bgs.ac.uk/africagroundwateratlas/downloadGIS.html '''Download a GIS shapefile of the Gambia geology and hydrogeology map'''].
 
 
 
There are two main aquifers in the Gambia: the upper Quaternary unconsolidated sands comprise a shallow sand aquifer (SSA), which is an important aquifer throughout the Gambia. The deeper Cretaceous sediments form a deep sandstone aquifer (DSA). More detail can be seen below.
 
 
 
[[File:Gambia_Hydrogeology3.png | center | thumb| 500px| Hydrogeology of the Gambia at 1:5million 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 Gambia geology and hydrogeology map].]]
 
  
  
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|}
 
|}
  
==Groundwater Status==
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===Groundwater Status===
 
 
 
Groundwater abstraction from the main unconsolidated aquifer (SSA) is less than average annual recharge. Total groundwater availability could be significantly increased by exploiting the DSA.
 
Groundwater abstraction from the main unconsolidated aquifer (SSA) is less than average annual recharge. Total groundwater availability could be significantly increased by exploiting the DSA.
  
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The same network is used to monitor groundwater quality.
 
The same network is used to monitor groundwater quality.
  
==References==
 
 
Other references relating to the hydrogeology of the Gambia can be found in the [https://www.bgs.ac.uk/africaGroundwaterAtlas/atlas.cfc?method=listResults&title_search=&author_search=&category_search=&country_search=GM&placeboolean=AND&singlecountry=1 Africa Groundwater Literature Archive].
 
 
===Geology References===
 
 
Whyte WJ and Russell TS. 1988. Geological and Mineral Map of The Republic of The Gambia. Ministry of Economic Planning and Industrial Development.
 
 
Whyte WJ and Russell TS. 1988. Geological Survey of The Gambia. Ministry of Local Government and Lands
 
 
===Hydrogeology References===
 
 
1983. Groundwater Resources of The Gambia, Preliminary Report. April 1983
 
 
Ceesay S and Humphreys H. 1987. Groundwater Survey Phase I.
 
 
 
==Return to the index pages==
 
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