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[[Africa Groundwater Atlas Home | Africa Groundwater Atlas]] >> [[Hydrogeology by country | Hydrogeology by country]]  >> Hydrogeology of Comoros
 
[[Africa Groundwater Atlas Home | Africa Groundwater Atlas]] >> [[Hydrogeology by country | Hydrogeology by country]]  >> Hydrogeology of Comoros
  
'''This page has limited information. If you have more recent information on the hydrogeology of Comoros, please get in touch!'''  
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'''This page has limited information and needs to be updated. If you have more recent information on the hydrogeology of Comoros, please get in touch!'''  
 
 
[[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]]]
 
 
 
 
 
Comoros is an archipelago nation of three major and numerous smaller volcanic islands islands off the east coast of Africa. Comoros and France dispute ownership of a fourth major island, Mayotte. The population is ethnically diverse as a result of centuries of immigration by Indonesian, Bantu African and Arabic peoples, among others.
 
 
 
In the first centuries of the second millennium AD, the islands were an important trade hub and stopover between Arabia and Africa. The pre-colonial economy was dominated by slave trading, which continued after France colonised Comoros in 1841, with the addition of plantation agriculture. Since independence from France in 1975 there have been multiple coups and widespread conflict. The island of Mayotte voted against independence in 1974 and 1976 by a large majority. The islands of Ndzuani and Mwali tried to become independent from the largest island of Ngazidja in 1997, since when they have experienced more autonomy, with each island having its own president within the overall union of the three islands.
 
The long term political, civil and military unrest means that development remains rudimentary, and Comoros i
 
s one of the world’s poorest countries. The economy of Comoros is dominated by agriculture, also including fishing, hunting and forestry, which contributes 40% of GDP and employs 80% of the labour force. Spices and the marine industry provide important export income, and the country is heavily dependent on external aid. The country is densely populated, although mostly rural.
 
 
 
Comoros has relatively high rainfall, although it is not evenly distributed seasonally. There are few rivers, and much of the population relies for water supplies on rainwater harvesting, stored in tanks and cisterns. These were traditionally uncovered, and many were contaminated by ash deposition after a volcanic eruption in 2006. Recent development activities have focussed on covering private water supply cisterns and raising awareness about protecting water resources from contamination.
 
 
 
  
 
==Compilers==
 
==Compilers==
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'''Dr Kirsty Upton''' and '''Brighid Ó Dochartaigh''', British Geological Survey, UK
 
'''Dr Kirsty Upton''' and '''Brighid Ó Dochartaigh''', British Geological Survey, UK
  
'''Dr Imogen Bellwood-Howard''', Institute of Development Studies, UK
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Please cite this page as: Upton & Ó Dochartaigh, 2016.
  
Please cite this page as: Upton, Ó Dochartaigh and Bellwood-Howard, 2018.
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Bibliographic reference: Upton, K. & Ó Dochartaigh, B.É. 2016. Africa Groundwater Atlas: Hydrogeology of Comoros. British Geological Survey. Accessed [date you accessed the information]. http://earthwise.bgs.ac.uk/index.php/Hydrogeology_of_Comoros
 
 
Bibliographic reference: Upton K, Ó Dochartaigh BÉ and Bellwood-Howard, I. 2018. Africa Groundwater Atlas: Hydrogeology of Comoros. British Geological Survey. Accessed [date you accessed the information]. http://earthwise.bgs.ac.uk/index.php/Hydrogeology_of_Comoros
 
  
 
==Terms and conditions==
 
==Terms and conditions==
  
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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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 and Conditions | Terms and Conditions]] for more information.
  
  
 
==Geographical Setting==
 
==Geographical Setting==
  
The largest islands of the Comoros archipelago are Ngazidja (Grande Comore), Ndzuani (Anjouan) and Mwali (Mohéli). Moroni, the capital, is on Ngazidja, the largest and westernmost island. The neighbouring island of Mayotte is under French administration.
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The Comoros archipelago includes Ngazidja (Grande Comore), Ndzuani (Anjouan) and Mwali (Mohéli). Moroni, the capital, is on Ngazidja, the largest and westernmost island. The neighbouring island of Mayotte is under French administration.
  
  
[[File:Comoros_Political.png | right | frame | Comoros. 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 For more information on the datasets used to develop the map see the [[Geography | geography resource page]]]]  
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[[File:Comoros_Political.png | right | frame | Comoros. For more information on the datasets used to develop the map see the [[Geography | geography resource page]]]]  
  
 
===General===
 
===General===
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{| class = "wikitable"
 
{| class = "wikitable"
 
|-
 
|-
|Capital city || Moroni
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|Estimated Population in 2013* || 734,917
 
|-
 
|-
|Region || Eastern Africa
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|Rural Population (% of total) (2013)* || 71.9%
 
|-
 
|-
|Border countries || none - Indian Ocean. Nearby countries are Mozambique, Madagascar, Tanzania and the Seychelles.
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|Total Surface Area* || 1,861 sq km
 
|-
 
|-
|Total surface area* ||1,861 km<sup>2</sup>  (186,100 ha)
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|Agricultural Land (% of total area) (2012)* || 84.9%
 
|-
 
|-
|Total population (2015)* || 788,900
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|Capital City || Moroni
 
|-
 
|-
|Rural population (2015)* ||570,600 (72%)
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|Region || Eastern Africa
 
|-
 
|-
|Urban population (2015)* || 217,900 (28%)
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|Border Countries || none - Indian Ocean. Nearby countries are Mozambique, Madagascar, Tanzania and the Seychelles.
 
|-
 
|-
|UN Human Development Index (HDI) [highest = 1] (2014)*|| 0.5032
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|Annual Freshwater Withdrawal (2013)* || 10 Million cubic metres
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|-
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|Annual Freshwater Withdrawal for Agriculture (2013)* || 47%
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|-
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|Annual Freshwater Withdrawal for Domestic Use (2013)* || 48%
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|-
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|Annual Freshwater Withdrawal for Industry (2013)* || 5%
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|-
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|Rural Population with Access to Improved Water Source (2012)* || 96.7%
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|-
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|Urban Population with Access to Improved Water Source (2012)* || n/a
 
|}
 
|}
  
<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===
 
===Climate===
  
[[File:Comoros_ClimateZones.png| 375x365px |Koppen Geiger Climate Zones]][[File:Comoros_ClimatePrecip.png| 375x365px |Average Annual Precipitation]][[File:Comoros_ClimateTemp.png| 375x365px |Average Temperature]]
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<gallery widths="375px" heights=365px mode=nolines>
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File:Comoros_ClimateZones.png|Koppen Geiger Climate Zones
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File:Comoros_ClimatePrecip.png|Average Annual Precipitation
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File:Comoros_ClimateTemp.png|Average Temperature
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</gallery>
  
[[File:Comoros_pre_Monthly.png| 255x124px| Average monthly precipitation for Comoros showing minimum and maximum (light blue), 25th and 75th percentile (blue), and median (dark blue) rainfall]] [[File:Comoros_tmp_Monthly.png| 255x124px| Average monthly temperature for Comoros showing minimum and maximum (orange), 25th and 75th percentile (red), and median (black) temperature]] [[File:Comoros_pre_Qts.png | 255x124px | Quarterly precipitation over the period 1950-2012]] [[File:Comoros_pre_Mts.png|255x124px | Monthly precipitation (blue) over the period 2000-2012 compared with the long term monthly average (red)]]
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[[File:Comoros_pre_Monthly.png| 255x124px| Average monthly precipitation for Comoros showing minimum and maximum (light blue), 25th and 75th percentile (blue), and median (dark blue) rainfall]] [[File:Comoros_tmp_Monthly.png| 255x124px| Average monthly temperature for Comoros showing minimum and maximum (orange), 25th and 75th percentile (red), and median (black) temperature]] [[File:Comoros_pre_Qts.png | 255x124px | Quarterly precipitation over the period 1950-2012]] [[File:Comoros_pre_Mts.png|255x124px | Monthly precipitation (blue) over the period 2000-2012 compared with the long term monthly average (red)]]  
 
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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]].
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For more information on the datasets used to develop these maps and graphs see the [[Climate | climate resource page]].
  
 
===Surface water===
 
===Surface water===
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{|
 
{|
 
|-
 
|-
| [[File:Comoros_soil.png | frame | Soil Map of Comoros, 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:Comoros_soil.png | frame | Soil Map of Comoros. For more information on the map see the [[Soil | soil resource page]]]]
  
 
|
 
|
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|
 
|
  
| [[File:Comoros_LandCover.png | frame | Land Cover Map of Comoros, 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:Comoros_LandCover.png | frame | Land Cover Map of Comoros. For more information on the map see the [[Land cover | land cover resource page]]]]
 
|}
 
|}
  
===Water statistics===
 
  
{| class = "wikitable"
 
| ||1997||1999||2012||2014||2015
 
|-
 
|Rural population with access to safe drinking water (%) || || ||  || || 89.1
 
|-
 
|Urban population with access to safe drinking water (%) || || ||  || || 92.6
 
|-
 
|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) || || ||  ||1522 ||
 
|-
 
|Total exploitable water resources (Million cubic metres/year) || || ||1,020||||
 
|-
 
|Freshwater withdrawal as % of total renewable water resources || ||0.8333 || || ||
 
|-
 
|Total renewable groundwater (Million cubic metres/year) ||  || || ||1,000 ||
 
|-
 
|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) || || ||  ||1,000 ||
 
|-
 
|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) || || ||  || ||
 
|-
 
|Groundwater: leaving the country to other countries (total) (Million cubic metres/year) || || || || ||
 
|-
 
|Industrial water withdrawal (all water sources) (Million cubic metres/year) || ||0.5 || || ||
 
|-
 
| Municipal water withdrawal (all water sources) (Million cubic metres/year)  || ||4.8 || || ||
 
|-
 
|Agricultural water withdrawal (all water sources) (Million cubic metres/year) || || 4.7|| || ||
 
|-
 
|Irrigation water withdrawal (all water sources)<sup>1</sup> (Million cubic metres/year) ||No data|| No data|| No data|| No data|| No data
 
|-
 
|Irrigation water requirement (all water sources)<sup>1</sup> (Million cubic metres/year) ||No data|| No data|| No data|| No data|| No data
 
|-
 
|Area of permanent crops (ha) || || ||  ||53,000 ||
 
|-
 
|Cultivated land (arable and permanent crops) (ha) || || ||  ||118,000||
 
|-
 
|Total area of country cultivated (%) || || ||  ||63.41 ||
 
|-
 
|Area equipped for irrigation by groundwater (ha) ||No data|| No data|| No data|| No data|| No data
 
|-
 
|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==
  
More information is available in the report [https://www.bgs.ac.uk/africaGroundwaterAtlas/atlas.cfc?method=ViewDetails&id=AGLA060004 UN (1988)] (see References section, below).  
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More information is available in the report [http://www.bgs.ac.uk/africagroundwateratlas/fulldetails.cfm?id=AGLA060004 UN (1988)] (see References section, below).  
  
 
The Comoros are volcanic basalt islands, the tips of a submerged range. There are at least three main phases of volcanic activity, separated by phases of rest and alteration. Almost the whole of Ngazidja island is covered with ouctrops of volcanic materials of the most recent upper phase, surrounded by lavas of the intermediate phase. At the ground surface there are also layers of red clay several metres thick, indicating advanced laterisation of the early phases (United Nations 1989).  
 
The Comoros are volcanic basalt islands, the tips of a submerged range. There are at least three main phases of volcanic activity, separated by phases of rest and alteration. Almost the whole of Ngazidja island is covered with ouctrops of volcanic materials of the most recent upper phase, surrounded by lavas of the intermediate phase. At the ground surface there are also layers of red clay several metres thick, indicating advanced laterisation of the early phases (United Nations 1989).  
  
The lavas of the later phase are compact or finely vesicular grey-black or iron-grey rocks, especially andesitic basalts, labradoric basalts, basanitoids and limburgites. The lavas of the intermediate phase are of a very common type; their mineralogical differentiation from the lavas of the upper phase is not always very clear. Scoria are often also found at the base of a flow; the middle part of a flow is more compact but fissured. The lava are sometimes extremely vesicular, as a result of cooling in the open air (United Nations 1989).
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The lavas of the later phase are compact or finely vesicular grey-black or iron-grey rocks, especially andesitic basalts, labradoric basalts, basanitoids and limburgites. The lavas of the intermediate phase are of a very common type; their mineralogical differentiation from the lavas of the upper phase is not always very
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clear. Scoria are often also found at the base of a flow; the middle part of a flow is more compact but fissured. The lava are sometimes extremely vesicular, as a result of cooling in the open air (United Nations 1989).
  
 
Small outcrops of alluvium, the result of sporadic surface water flows, are found in the form of fine materials produced by the recapture of pyroclastic materials or very coarse materials shaped by the action of torrents (United Nations 1989).  
 
Small outcrops of alluvium, the result of sporadic surface water flows, are found in the form of fine materials produced by the recapture of pyroclastic materials or very coarse materials shaped by the action of torrents (United Nations 1989).  
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==Hydrogeology==
 
==Hydrogeology==
  
More information on the hydrogeology of Comoros is available in the report [https://www.bgs.ac.uk/africaGroundwaterAtlas/atlas.cfc?method=ViewDetails&id=AGLA060004 UN (1988)] (see References section, below).  
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More information on the hydrogeology of Comoros is available in the report [http://www.bgs.ac.uk/africagroundwateratlas/fulldetails.cfm?id=AGLA060004 UN (1988)] (see References section, below).  
  
 
The basaltic lavas have high permeability. Other formations are thought to be of little hydrogeological interest. Direct rainfall recharge is likely to be rapid and high, infiltrating down to the aquifer base roughly at sea level (United Nations 1989). The degree of alteration of the volcanic rocks, and therefore their
 
The basaltic lavas have high permeability. Other formations are thought to be of little hydrogeological interest. Direct rainfall recharge is likely to be rapid and high, infiltrating down to the aquifer base roughly at sea level (United Nations 1989). The degree of alteration of the volcanic rocks, and therefore their
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==References==
 
==References==
  
References with more information on the geology and hydrogeology of Comoros can be accessed through the [https://www.bgs.ac.uk/africaGroundwaterAtlas/atlas.cfc?method=listResults&title_search=&author_search=&category_search=&country_search=KM&placeboolean=AND&singlecountry=11 Africa Groundwater Literature Archive].
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References with more information on the geology and hydrogeology of Comoros can be accessed through the [http://www.bgs.ac.uk/africagroundwateratlas/searchResults.cfm?title_search=&author_search=&category_search=&country_search=KM&placeboolean=AND&singlecountry=11 Africa Groundwater Literature Archive].
 
 
United Nations. 1989. [https://www.bgs.ac.uk/africaGroundwaterAtlas/atlas.cfc?method=ViewDetails&id=AGLA060004 Groundwater in Eastern, Central and Southern Africa: Comoros]. United Nations Department of Technical Cooperation for Development.
 
  
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United Nations. 1989. [http://www.bgs.ac.uk/africagroundwateratlas/fulldetails.cfm?id=AGLA060004 Groundwater in Eastern, Central and Southern Africa: Comoros]. United Nations Department of Technical Cooperation for Development. 
  
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==Return to the index pages==
 
[[Africa Groundwater Atlas Home | Africa Groundwater Atlas]] >> [[Hydrogeology by country | Hydrogeology by country]]  >> Hydrogeology of Comoros
 
[[Africa Groundwater Atlas Home | Africa Groundwater Atlas]] >> [[Hydrogeology by country | Hydrogeology by country]]  >> Hydrogeology of Comoros
  
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