Hydrogeology of Democratic Republic of the Congo: Difference between revisions
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==Hydrogeology== | ==Hydrogeology== | ||
This section provides a summary of the hydrogeology of the main aquifers in the Democratic Republic of the Congo. More information is available in the report [https://www.bgs.ac.uk/africagroundwateratlas/fulldetails.cfm?id=AGLA060006 | This section provides a summary of the hydrogeology of the main aquifers in the Democratic Republic of the Congo. More information is available in the report [https://www.bgs.ac.uk/africagroundwateratlas/fulldetails.cfm?id=AGLA060006 United Nations (1989)] (see References section, below). | ||
The hydrogeology map 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). | The hydrogeology map 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). |
Revision as of 12:06, 29 September 2015
Africa Groundwater Atlas >> Hydrogeology by country >> Hydrogeology of the Democratic Republic of the Congo
Some of the textual information on this page was taken from the chapter on the Democratic Republic of the Congo (then Zaire) in the report ‘Groundwater in Eastern, Central and Southern Africa’ (UN 1989). This information is outdated. If you have more recent information on the hydrogeology of the Democratic Republic of the Congo, please get in touch.
Compilers
Dr Kirsty Upton and Brighid Ó Dochartaigh, British Geological Survey, UK
Geographical Setting
The central part of the country is a large basin ranging in altitude from 350 to 700 m above sea level, with broad steep-sided valleys. To the east of this basin is a mountain ridge from 2300 to 3800 m above sea level that marks the edge of the East African Rift. To the south are the high Kasai and Shaba plateaus, from 1000 to 2000m above sea level. To the west are the Mayumbe hills, around 750 m in elevation, with narrow cols and valleys. To the north the basin is bounded by the watershed of the Oubangui river. The coastal area in the west, on the Atlantic Ocean, contains largely low land and sandy beaches, or cliffs.
General
Estimated Population in 2013* | 67,513,677 |
Rural Population (% of total) (2013)* | 58.5% |
Total Surface Area* | 2,267,050 sq km |
Agricultural Land (% of total area) (2012)* | 11.5% |
Capital City | Kinshasa |
Region | Central Africa |
Border Countries | Republic of the Congo, Central African Republic, South Sudan, Uganda, Rwanda, Burundi, Tanzania, Zambia, Angola |
Annual Freshwater Withdrawal (2013)* | 683.6 Million cubic metres |
Annual Freshwater Withdrawal for Agriculture (2013)* | 10.5% |
Annual Freshwater Withdrawal for Domestic Use (2013)* | 68% |
Annual Freshwater Withdrawal for Industry (2013)* | 21.5% |
Rural Population with Access to Improved Water Source (2012)* | 29% |
Urban Population with Access to Improved Water Source (2012)* | 79.1% |
* Source: World Bank
Climate
The Democratic Republic of the Congo lies on the equator. Average temperatures across much of the country are around 25 degrees C, except in the eastern mountains where average temperatures are around 20 degrees C. There is much cloud cover over much of the year, with the maximum sunshine in the dry season.
Average annual rainfall for the whole country is over 1,200 mm, rising to more than 2,000 mm in the central basin, and falling to a minimum of around 850 mm at the western coast. There is a single rainy season, from September to June in the south and from February to November in the north; and a single dry season, in june and July in the south and December and January in the north.
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Koppen Geiger Climate Zones
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Average Annual Precipitation
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Average Temperature
For further detail on the climate datasets used see the climate resources section.
Surface water
The Congo river - the largest river basin in Africa - drains all surface water in the country. It has many large tributaries, many of which have been dammed for hydroelectric power production. |
Soil
Land cover
Geology
This section provides a summary of the geology of the Democratic Republic of the Congo. More information is available in the report UN (1989). (see References section, below).
The geology map shows a simplified version of the geology at a national scale (see the Geology resources page for more details).
Summary
The oldest rocks are Precambrian in age, of various types but all variously metamorphised and deformed. Overlying this are unmetamorphosed, largely undeformed sedimentary rocks, from Palaeozoic (largely Upper Carboniferous) to Quaternary age. There are also small areas of Quaternary volcanic rocks in the far east associated with the East African Rift. Across much of the country there is a cover of Tertiary to Quaternary sediments which are largely unconsolidated, including valley alluvium and lateritic gravels.
Key Formations | Period | Lithology | |
Sedimentary, largely unconsolidated | |||
---|---|---|---|
Alluvium, lacustrine, aeolian lateritic and other unconsolidated deposits | Tertiary to Quaternary | Fine to coarse sands and gravels; clays and sandy clays. In some areas, such as underlying the Batékés Plateau and southeast Kasaï, the sediments consist mainly of semi-continuous sandy loam and soft sandstone (Partow 2011). | |
Sedimentary, consolidated | |||
Soft sandstones and argillaceous rocks | Cretaceous | ||
Well-consolidated sandstones and argillaceous rocks | Upper Carboniferous to Jurassic | Karoo-type sandstones and in some cases calcareous rocks. | |
Precambrian | |||
Metasedimentary rocks | Precambrian | Metamorphosed quartzites, schists, limestones, dolomitic limestones and dolomites. The calcareous rocks are often karstic. | |
Crystalline granitic and metamorphic rocks | Precambrian | Crystalline granitic and metamorphic basement rocks, part of the African Craton |
Hydrogeology
This section provides a summary of the hydrogeology of the main aquifers in the Democratic Republic of the Congo. More information is available in the report United Nations (1989) (see References section, below).
The hydrogeology map 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).
Unconsolidated or Consolidated Sedimentary - Intergranular Flow
Named Aquifers | General Description |
Alluvial sands and gravels; lateritic gravels; aeolian sands; other sand and gravel deposits | Boreholes in unconsolidated sands and gravels, between 5 and 15 m thick, have recorded specific yield values of 1.5 to 10 m³/hour/m of drawdown; transmissivity 0.1.65 x 10-3 (United Nations 1989).
In the Cuvette Centrale and Oubangui areas, coarse alluvial sediments up to 120 m thick occur, with recharge from direct rainfall infiltration and indirectly from river infiltration. Areas which are known to have particularly good potential include Libenge and the alluvial plain between the N’Djili River and Ngaliema Bay in Kinshasa (Partow 2011). The Tertiary-Quaternary aquifer underlying the Batékés Plateau and southeast Kasaï, consisting mainly of semi-continuous sandy loam and soft sandstone, is up to 100 m thick. It has relatively low productivity, although it sustains many streams by baseflow. Recharge is largely from direct rainfall infiltration (Partow 2011).
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Sedimentary - Intergranular & Fracture Flow
Named Aquifers | General Description |
Cretaceous and Mesozoic-Palaeozoic sandstones | A borehole in soft Cretaceous sandstones, which have layers of argillaceous material, was recorded at 160 m deep, with a specific yield value of 4 m³/hour/m of drawdown; transmissivity value of 130 m²/day, and a storage coefficient of 6.5 x 10-4 (United Nations 1989).
Mesozoic Karoo-type sandstone and calcareous aquifers, which occur in large parts of the Cuvette Centrale, including around Gemena, Kisingani and northern Kasaï, receive rapid recharge. They have low to moderate productivity. In certain areas, fracturing has led to the development of karstic systems, which have higher productivity (Partow 2011). Groundwater is likely to be low in dissolved solids and minerals (Partow 2011). |
Sedimentary - Fracture Flow
Named Aquifers | General Description |
Metamorphosed limestones and dolomitic limestones, including the Lubumbashi dolomites; quartzites and other non-calcareous rocks | Karstic metamorphosed limestones and dolomitic limestones can form highly productive aquifers, dominated by rapid karstic flow, such as the Lubumbashi dolomites in southern Katanga (Partow 2011). Boreholes up to 150 m deep are recorded, with specific yield values of 3 to 11 m³/hour/m of drawdown; a transmissivity value of 130 m²/day, and a storage coefficient of 0.3 x 10-5 (United Nations 1989).
Non-karstic Precambrian metasedimentary rocks typically form low productivity aquifers, possibly locally moderately productive where there is extensive fracturing. Karstic and carbonate aquifers have alkaline groundwater. Where there are sulphide minerals in the rock, as in some schists, or in gypsum, as found at Katanga, groundwater can be highly mineralised (Partow 2011). |
Basement
Named Aquifers | General Description |
Precambrian Basement | Crystalline basement rocks. Forms local aquifers in weathered and/or fractured zones, usually low producivity but occasionally moderate. The aquifer properties are controlled by the depth of weathering (regolith) and the degree of fracturing of unweathered bedrock. Fractured bedrock alone can sometimes supply relatively good yields, but has low storage and cannot sustain these yields in the long term. Weathered regolith provides additional storage.
Groundwater typically has low levels of mineralisation and a below-neutral pH (Partow 2011). |
Groundwater Status
Most of the information in this section is taken from Partow (2011), who provides a detailed overview of water issues in the country (see Reference section, below).
Information on the extent and quality of groundwater resources and springs in the Democratic Republic of the Congo is scarce, and where available is often outdated and of limited geographic coverage (Partow 2011).
However, the available information points to pressures on groundwater resources in some areas. Increasing water demand, combined in some cases with drought-prone areas, has led to seasonal water shortages in some areas (Partow 2011).
Groundwater use and management
Most of the information in this section is taken from Partow (2011), who provides a detailed overview of water issues in the country (see Reference section, below).
Groundwater use
Despite the abundance of surface waters, and the fact that up to date and accurate information on water use in the country is not availabel (Partow 2011), the vast majority of the population - some 90 percent - is thought to be dependent on groundwater for drinking water, mainly from springs (Partow 2011). These springs are mainly simple capped spring heads, and are used both in rural villages and in the rapidly growing peri-urban areas. Large-scale water production from springs through distribution networks is also an important water source for many cities, including Mbuji-Mayi, Lubumbashi, Kisingani, Bunia, Beni, Gemena and Lisala (Partow 2011).
Groundwater is also abstracted from hand dug wells, using hand pumps or mechanical pumps. Groundwater from wells is estimated to account for approximately 10 percent of the country's drinking water supply (Partow 2011).
There are only an estimated 1,000 deep-drilled boreholes in the country, most of which were drilled between the 1960s and 1980s, especially during the International Decade for Water Supply and Sanitation. They abstract from various aquifers, with yields ranging from 15 to 300 m³/h (United Nations 1989) (although mostly from 15 to 80 m³/h - Partow, 2011). Since the 1990s, limited borehole drilling has been carried out, though in the past several years it has been rapidly developing with international assistance.
Groundwater monitoring
There is no inventory of springs at national and provincial levels (Partow 2011).
Groundwater legislation and management
Partow (2011) provides a detailed discussion of the water sector in the Democratic Republic of the Congo as of 2010, including responsible bodies and legislation and how these are changing.
Transboundary aquifers
The Democratic Republic of the Congo shares a number of aquifers with neighbouring countries. These include (Altchenko and Vilholth 2013):
- the Kalahari/Katanga basin, shared with Zambia;
- the Congo/Zambezi basin, shared with Angola;
- the Tanganyika aquifer, shared with Tanzania, Rwanda and Burundi;
- the Precambrian dolomitic aquifer, shared with Angola;
- a coastal sedimentary aquifer shared with Angola;
- the Cuvette Centale aquifer, shared with the Congo;
- the Mgahinga aquifer, shared with Rwanda and Uganda; and
- the Western Rift Valley Sediment aquifer, shared with Uganda.
For further information about transboundary aquifers, please see the Transboundary aquifers resources page
References
The following references provide more information on the geology and hydrogeology of the Democratic Republic of the Congo.
These, and others, can be accessed through the Africa Groundwater Literature Archive
Altchenko Y and Vilholth KG. 2013. Transboundary aquifer mapping and management in Africa: a harmonised approach. Hydrogeology Journal Vol.21, Issue 7, pp. 1497-1517.
United Nations. 1989. Groundwater in Eastern, Central and Southern Africa: Zaire. United Nations Department of Technical Cooperation for Development, Natural Resources/Water Series No.19, ST/TCD/6.
Partow H. 2011. Water issues in the Democratic Republic of Congo: Challenges and Opportunities. United Nations Environment Programme Technical Report
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