Hydrogeology of Guinea Bissau
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Present-day Guinea Bissau was once part of the Gabu kingdom and the ancient Mali empire. From the 15th century, the coast became a centre of slave trading by Portuguese merchants, which, as well as inland areas, became fully colonised by the Portuguese in the 19th century. An armed rebellion against colonial rule from the 1950s led to independence in 1974. The rebels were allied to an extent with independence fighters from another Portuguese colony, Cape Verde, although the two countries never unified. Since independence, Guinea Bissau has experienced constant political change, with a succession of coups.
Guinea Bissau adopted the CFA currency in 1997. There is some potential for mineral exploitation and possibly offshore hydrocarbon exploitation, but their development has been impeded by political instability and armed conflict. The economy remains dominated by agriculture and fishing, with cashew nuts and groundnuts the most important export crops. GDP and HDI remain some of the lowest world-wide. Illegal drug trafficking is significant, with the country used as a transit point for drugs between South America and Europe.
A tropical country with high but seasonal rainfall, Guinea Bissau has relatively abundant seasonal surface water resources, but dry season water supplies are largely sourced from groundwater.
- 1 Compilers
- 2 Terms and conditions
- 3 Geographical Setting
- 4 Geology
- 5 Hydrogeology
- 6 Groundwater use and management
- 7 References
- 8 Return to the index pages
Dr Kirsty Upton and Brighid Ó Dochartaigh, British Geological Survey, UK
Dr Imogen Bellwood-Howard, Institute of Development Studies, UK
Please cite this page as: Upton, Ó Dochartaigh and Bellwood-Howard, 2018.
Bibliographic reference: Upton, K, Ó Dochartaigh, B É and Bellwood-Howard, I. 2018. Africa Groundwater Atlas: Hydrogeology of Guinea Bissau. British Geological Survey. Accessed [date you accessed the information]. http://earthwise.bgs.ac.uk/index.php/Hydrogeology_of_Guinea_Bissau
Terms and conditions
Guinea Bissau's territory includes the Bijagos archipelago, made up of more than 30 offshore islands. Most of the country is flat and low lying, with a maximum elevation of 40 m, and many areas of wetlands, including coastal mangrove swamps. The exception is the flat topped Boé Colline hills in the southeast, which reach 300 m elevation.
|Border countries||Senegal, Guinea|
|Total surface area*||36,130 km2 (3,613,000 ha)|
|Total population (2015)*||1,844,000|
|Rural population (2015)*||962,000 (52%)|
|Urban population (2015)*||882,000 (48%)|
|UN Human Development Index (HDI) [highest = 1] (2014)*||0.4196|
* Source: FAO Aquastat
Guinea Bissau has a wet tropical climate, with a wet season typically from April to October and a dry season from November to March. The eastern part of the country has lower rainfall, and the western coastal zone has higher rainfall.
More information on average rainfall and temperature for each of the climate zones in Guinea Bissau can be seen at the Guinea Bissau 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 resource page.
The larger rivers in Guinea Bissau include the Corubal and the Geba rivers, which rise in neighbouring Senegal or Guinea. Smaller coastal rivers include the Cacheu, Mansoa, Geba-Corubal, Grande de Buba, Tombali, Cumbidja and Cacine rivers.
|Much of Guinea Bissau was originally dominated by wooded savannah and forest, but there has been widespread clearance of forest and woodland in recent decades, for local or exportable timber use or for cultivation.|
|Rural population with access to safe drinking water (%)||60.3|
|Urban population with access to safe drinking water (%)||98.8|
|Population affected by water related disease||No data||No data||No data||No data||No data||No data|
|Total internal renewable water resources (cubic metres/inhabitant/year)||8,677|
|Total exploitable water resources (Million cubic metres/year)||No data||No data||No data||No data||No data||No data|
|Freshwater withdrawal as % of total renewable water resources||0.5573|
|Renewable groundwater resources (Million cubic metres/year)||350|
|Groundwater produced internally (Million cubic metres/year)||14,000|
|Fresh groundwater withdrawal (primary and secondary) (Million cubic metres/year)||31|
|Groundwater: entering the country (total) (Million cubic metres/year)||No data||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||No data|
|Industrial water withdrawal (all water sources) (Million cubic metres/year)||11.9|
|Municipal water withdrawal (all water sources) (Million cubic metres/year)||34.1|
|Agricultural water withdrawal (all water sources) (Million cubic metres/year)||144|
|Irrigation water withdrawal (all water sources) 1 (Million cubic metres/year)||No data||No data||No data||No data||No data||No data|
|Irrigation water requirement (all water sources) 1 (Million cubic metres/year)||26.3|
|Area of permanent crops (ha)||250,000|
|Cultivated land (arable and permanent crops) (ha)||550,000|
|Total area of country cultivated (%)||15.22|
|Area equipped for irrigation by groundwater (ha)||530|
|Area equipped for irrigation by mixed surface water and groundwater (ha)||7,371|
These statistics are sourced from 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 Aquastat Main Database.
1 More information on irrigation water use and requirement statistics
The geology map below shows a simplified version of the geology of Guinea Bissau at 1:5 million scale (see the Geology resources page for more details).
A more detailed geology map of Guinea Bissau is available to view and interrogate online at the Visualizador de Mapas geoPortal (published 2014). This map was created by the Uidade de Informacao Geocientifica of the Portugese National Laboratory of Energy and Geology (LNEG).
This report provides more information on the Geology of Guinea Bissau (Geologia da Guiné-Bissau) (Alves 2010).
Guinea-Bissau lies between the Fouta Djallon massif, of uncertain Palaeozoic age, and the Mesozoic-Cenozoic Senegal basin (UN 1988). It can be roughly divided into two geological units:
- an eastern zone with predominantly clastic sedimentary Paleozoic rocks, and some carbonates of Silurian age; and some Precambrian rocks; and
- a western zone with mainly late Mesozoic to Cenozoic sediments. The Cretaceous to Cenozoic sediments are mainly of marine origin (University of Guelph).
|Quaternary||Coastal sediments, including beach sands; river and coastal alluvium. Including sands, silts, and clays.|
|Upper Cretaceous - Tertiary sedimentary|
|Maastrichtian, Palaeocene-Eocene, Oligocene, Miocene||A sequence of largely marine sedimentary rocks, including limestones, marls, clays, silts, sands and phosphates. Drilling investigations have proved a ~5m thick phosphate layer in the Palaeocene-Eocene sequence, with 25-50m of overlying sediments.|
|Little is known of the igneous rocks in Guinea-Bissau.|
|Devonian||Shales and sandstones, including the Upper Devonian Bafata Group, and Lower Devonian sandstones in the Cusselinta-Saltinho area.|
|Silurian||Rocks of the Buba Group, including sandstones with some organic rich/carbonaceous black shales.|
|Cambrian-Ordovician||Sandstones, shales, conglomerates and rare limestones.|
|Precambrian metamorphic complex|
|Neoproterozoic||A volcanic and metasedimentary complex, including schists, quartzites and metavolcanic rocks.|
The hydrogeology map below shows a simplified version of the type and productivity of the main aquifers at a national scale (see the hydrogeology map resource page for more details).
More information on the hydrogeology of Guinea Bissau is available in the report United Nations (1988) (see References section, below).
|Quaternary (to Tertiary)|
Sedimentary - Mixed Intergranular and Fracture flow
Sedimentary - Fracture flow
Groundwater use and management
Groundwater is the main source of rural water supply in the dry season, for drinking water and small scale (garden) irrigation.
Traditional small scale irrigation typically uses groundwater from shallow, hand dug wells. Groundwater is not used much for large scale commercial irrigation, although in at least one area - Granja de Pessub - drilled boreholes up to 300 m deep are used for irrigation (Aquastat).
The main agencies involved in water management in Guinea Bissau are (http://www.fao.org/nr/water/aquastat/countries_regions/GNB/ Aquastat):
- the Ministry of Agriculture, Forestry, Hunting and Livestock, through the Directorate of Rural Engineering Services (DSER), which deals with the developments use and management of water for agricultural use.
- the Directorate General of Water Resources of the State Secretariat for Industry, Natural Resources and the Environment (SEIRNA)
- the Council Interministerial for Water Resources (CIMA) and the Water Technical Committee, which exist to harmonise water management activities between different sectors and to drive water policies.
At a local level, the operation of water infrastructure is largely managed by the beneficiaries themselves through associations or management committees, in collaboration with the DSER, extension services, NGOs and other relevant authorities.
The Water Code, 1992, established the general regime for the management, use and conservation of water resources, and determines the institutional framework. It recognises that water is a public good whose development and management must be planned. Use rights are granted by the State, taking into account the productivity of water, the respect of pre-existing rights and the protection of the environment. The State is responsible for the conservation and protection of the water environment both qualitatively and quantitatively. Customary water law is enforced and respected at the local level by rural people.
For further information about transboundary aquifers, please see the Transboundary aquifers resources page.
References with more information on the geology and hydrogeology of Guinea Bissau can be accessed through the Africa Groundwater Literature Archive.
Alves PH. 2010. Geologia da Guinée-Bissau. X Congresso de Geoquimica dos Paises de Lingua Portuguesa, XVI Semana de Geoquimica. LNEG – Laboratório Nacional de Energia e Geologia / IICT – Instituto de Investigação Científica Tropical
Fussi F, Asplund F, Fumagalli L, Caruba M, Rotiroti M and Bonomi T. 2017. Characterization of shallow aquifer in Guinea Bissau to support the promotion of manual drilling at country level. Presentation at 44th IAH Congress, 25-29 Sept 2017.
University of Guelph. Rocks for Crops.
WES. Guinea Bissau: Country Profile. Water, Environment and Sanitation (WES), UNICEF.
United Nations. 1988. Groundwater in North and West Africa: Guinea-Bissau. United Nations Department of Technical Cooperation for Development and Economic Commission for Africa.