Hydrogeology of Democratic Republic of the Congo: Difference between revisions

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The geology map shows a simplified version of the geology at a national scale (see [[Geology | the Geology resources page]] for more details).
The geology map shows a simplified version of the geology at a national scale (see [[Geology | the Geology resources page]] for more details).


  [[File:DRC_Geology2.png | center]]
  [[File:DRC_Geology2.png | center |500px]]


'''Summary'''
'''Summary'''
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The oldest rocks are part of the African Craton, including granites, gabbros and similar igneous and metamorphic rocks.
The oldest rocks are part of the African Craton, including granites, gabbros and similar igneous and metamorphic rocks.
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==Hydrogeology==
==Hydrogeology==

Revision as of 11:05, 23 September 2015

Africa Groundwater Atlas >> Hydrogeology by country >> Hydrogeology of the Democratic Republic of the Congo


Most 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 This information is outdated.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.

Map of the Democratic Republic of the Congo (For more information on the datasets used in the map see the geography resources section)

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.


Average monthly precipitation for the Democratic Republic of the Congo showing minimum and maximum (light blue), 25th and 75th percentile (blue), and median (dark blue) rainfall Average monthly temperature for the Democratic Republic of the Congo showing minimum and maximum (orange), 25th and 75th percentile (red), and median (black) temperature Quarterly precipitation over the period 1950-2012 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 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.

Surface Water Map of the Democratic Republic of the Congo (For more information on the datasets used in the map see the surface water resources section)

Soil

Soil Map of the Democratic Republic of the Congo (For map key and more information on the datasets used in the map see the soil resources section)

Land cover

Land Cover Map of COUNTRY (For map key and more information on the datasets used in the map see the land cover resources section)

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.


Geological Environments
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.
Sedimentary, consolidated
Soft sandstones and argillaceous rocks Cretaceous
Well-consolidated sandstones and argillaceous rocks Upper Carboniferous to Jurassic
Basement
Craton; Mobile/Orogenic Belt; and Metasedimentary units Precambrian The youngest rocks in this series are metasedimentary (metamorphosed quartzites, schists, etc), which still show sedimentary features such as palaeobedding. They include metalimestones and dolomitic limestones, which are sometimes karstic.

There are intermediate aged rocks classed as Mobile/Orogenic Belt, which have been subject to extensive metamorphism and deformation, and which show metamorphic foliation; jointing and folding.

The oldest rocks are part of the African Craton, including granites, gabbros and similar igneous and metamorphic rocks.

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 UN (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 Aquifer properties 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

Sedimentary - Intergranular Flow

Named Aquifers General Description

Sedimentary - Intergranular & Fracture Flow

Named Aquifers General Description
Cretaceous and Mesozoic-Palaeozoic sandstones Boreholes in soft Cretaceous sandstones, which have layers of argillaceous material, are recorded at up to 160 m deep, with specific yield values of 4 m³/hour/m of drawdown; transmissivity values of 130 m²/day, and storage coefficients of 6.5 x 10-4<\sup> (United Nations 1989).


Sedimentary - Fracture Flow

Named Aquifers General Description
Metamorphosed limestones and dolomitic limestones; quartzites Metamorphosed limestones and dolomitic limestones are sometimes karstic and can form highly productive aquifers, dominated by rapid karstic flow. Boreholes up to 150 m deep are recorded, with specific yield values of 11 m³/hour/m of drawdown; transmissivity values of 130 m²/day, and storage coefficients of 0.3 x 10-5<\sup> (United Nations 1989).

Non-karstic Precambrian metasedimentary rocks typically form low productivity aquifers, possibly locally moderately productive where there is extensive fracturing.

Basement

Named Aquifers General Description
Precambrian Craton and Mobile/Orogenic Belt Crystalline basement rocks. Forms low producivity, local aquifers in weathered and/or fractured zones. 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.

The regolith is typically 10 to 15 m thick, but can be up to 30 m thick. Below this, the unweathered bedrock can be fractured to depths of about 60 - 70 m (United Nations 1989). The water table is usually 20 to 30 m below the ground surface. Boreholes tend to be 50 to 60 m deep. An average transmissivity value of 5.7 m²/day is given. Yields are typically very low to low: between 0.2 and 2 l/s. One study reported the average yield from 106 boreholes to be 1.4 l/s, with 44% of the boreholes yielding less than 1 l/s and just 3% yielding 3 l/s or more (United Nations 1989).


Groundwater Status

Groundwater quantity

Groundwater quality

Groundwater use and management

Groundwater use

Groundwater management

Groundwater monitoring

Transboundary aquifers

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

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.


Return to the index pages

Africa Groundwater Atlas >> Hydrogeology by country >> Hydrogeology of the Democratic Republic of the Congo