Hydrogeology of Angola
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Você pode ler esta página em português Hidrogeologia de Angola
Compilers
Dr Kirsty Upton and Brighid Ó Dochartaigh, British Geological Survey, UK
Please cite this page as: Upton and Ó Dochartaigh, 2016.
Bibliographic reference: Upton, K, and Ó Dochartaigh, B É. 2016. Africa Groundwater Atlas: Hydrogeology of Angola. British Geological Survey. Accessed [date you accessed the information]. https://earthwise.bgs.ac.uk/index.php/Hydrogeology_of_Angola
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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 Terms of use for more information.
Geographical setting
General
Angola is in central-southern Africa. There is a lowland coastal strip between 35 and 180 km wide that ranges from 300 to 500 m in elevation. Away from this, most of the country is formed of high plateaus from about 1000 to 1800 m in elevation, with the highest point at 2620 m. Hills and mountains rise inland from the coast into a major escarpment. Extending eastwards and south-eastwards from the escarpment is a large area of high plateau (planalto).
Estimated population in 2013* | 21 471 618 |
Rural population (% of total) (2013)* | 57.5% |
Total surface area* | 1 246 700 sq km |
Agricultural land (% of total area) (2012)* | 47.5% |
Capital city | Luanda |
Region | Central Africa |
Border countries | Namibia, the Democratic Republic of the Congo, Zambia |
Annual freshwater withdrawal (2013)* | 708.8 million cubic metres |
Annual freshwater withdrawal for agriculture (2013)* | 20.8% |
Annual freshwater withdrawal for domestic use (2013)* | 45.3% |
Annual freshwater withdrawal for industry (2013)* | 33.9% |
Rural population with access to improved water source (2012)* | 34.3% |
Urban population with access to improved water source (2012)* | 67.6% |
* Source: World Bank
Climate
Most of Angola has a dry season from May to October and a rainy season from February to April, with transitional rains from November to January. The south of the country, and along parts of the coastal strip, are semi-arid, with less than 400 mm/year of rain. The far north sees rainfall throughout much of the year, with more than 1400 mm/year of rain. The climate is greatly influenced by prevailing winds from the west and south-west.
More information on average rainfall and temperature for each of the climate zones in Angola can be seen on the Angola 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 on the datasets used to develop these maps and graphs see the climate resource page.
Surface water
The centre and north of Angola have many perennial rivers. In the south there are only three perennial rivers: the Cunene, Kuando and Cubango (which flows to the Okavango) rivers. The Zambezi River and several tributaries of the Congo River have their sources in Angola. Many rivers originate in the central uplands, but take quite different flow paths. Some flow more or less due westerly to the Atlantic, providing water for irrigation and the potential for hydroelectric power in the dry coastal strip. Two of the largest rivers, the Cuanza and the Cunene, take a more indirect route to the Atlantic, the Cuanza flowing north and the Cunene flowing south before turning west. navigable. The Kwango and other rivers flow north from the high plateau to join the Kasai River (one of the largest tributaries of the Congo). Some rivers flow south into the Zambezi River system and from there to the Indian Ocean; others to the Okavango River (called the Cubango River in Angola) and thence to the Okavango Swamp in Botswana.
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Soil
Land cover
In the far south and south-west of Angola, land cover is dominated by desert or sparse savannah or grassland vegetation. This gives way northwards to shrubland and then to a mix of shrubland then to deciduous forest, which covers much of the rest of the country.
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Geology
This section provides a summary of the geology of Angola. More information is available in the report ‘Groundwater in Eastern, Central and Southern Africa’ (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).
Key formations | Period | Lithology | |
Unconsolidated/Semi-consolidated | |||
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Alluvium | Quaternary | Unconsolidated alluvial sediments infilling valleys. | |
Tertiary–Quaternary | Kalahari Group | Loosely consolidated sandstones and unconsolidated sands and silts, covering much of the eastern part of the country. Up to 600 m thick. | |
Consolidated sedimentary | |||
Cretaceous–Tertiary | Up to 150 m thickness of Aptian-Maastrichtian age sedimentary rocks, often argillaceous sandstones with marine and evaporitic deposits. Overlain by up to 1200 m thickness of Paleocene to Pliocene age sedimentary rocks. | ||
Karoo Supergroup | Carboniferous–Jurassic | Argillaceous limestones, sandstones and shales at the edge of Congo Basin. Up to 500 m thick. Intruded by dolerites. | |
Volcanic rocks | |||
Mesozoic | |||
Precambrian | |||
Bembé System | Late Precambrian–Lower Cambrian | Metasedimentary rocks: schist-limestones overlain by metasandstones, metaconglomerates and quartzites | |
Oendolongo System | Precambrian | Metasedimentary rocks: quartzitic metasandstones | |
Crystalline basement | Archaean | Crystalline igneous and metamorphic rocks, largely granites, gneisses and gabbros, part of the African craton. Often quartz veins. |
Hydrogeology
This section provides a summary of the hydrogeology of the main aquifers in Angola. More information is available in the report ‘Groundwater in Eastern, Central and Southern Africa’ (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 Hydrogeology Map resource page for more details).
A hydrogeological map of Angola at 1:1 500 000 scale was published by Hidroprojecto Consultores de Hidraulica e Salubridade SA (1990) (see Reference section, below).
Angola is also covered by the SADC hydrogeological map and atlas (2010), available through the SADC Groundwater Information Portal.
Unconsolidated Aquifers
Named aquifers | Period | General description | Water quality |
Alluvium | Quaternary | Variable groundwater potential, from low productivity to high productivity aquifers. Aquifer productivity depends on the aquifer lithology (whether dominated by permeable sands and gravels or low permeability fine-grained deposits), thickness and lateral (areal) extent. |
Sedimentary Aquifers - Intergranular flow
Named aquifers | Period | General description | Water quality |
Kalahari Group | Tertiary–Quaternary | Thought to form a moderate to high productivity aquifer. The water table in the Kalahari Group is shallower in the north, and becomes deeper towards the south, where the Kalahari Group is typically completely dry (Groundwater Consultants Bee Pee (Pty) Ltd, SRK Consulting (Pty) Ltd, 2002). |
Sedimentary Aquifers - Intergranular and fracture flow
Named aquifers | Period | General description | Water quality |
unnamed small aquifers along the coast | Cretaceous–Tertiary | Argillaceous sandstones along the coast have proved to be moderately productive aquifers. | Groundwater can be relatively highly mineralised, sometimes associated with salt-bearing formations. |
Karoo Supergroup (inland) | Carboniferous–Jurassic | These can form productive aquifers. | Groundwater can be relatively highly mineralised |
Basement Aquifers
Named aquifers | Period | General description | Water quality |
Crystalline basement and metasedimentary rocks | Precambrian (locally Lower Cambrian) | Basement rocks form local aquifers, generally with low productivity but sometimes up to moderate productivity. Groundwater is only found where the rocks are fractured and/or weathered. The best groundwater potential is in zones of quartz veins and basic rocks; contact zones between crystalline rocks of different texture and composition; zones of fractured granitogneiss; and contact zones between metavolcanic and quartz-schist rocks.
Although borehole yields are generally low, some boreholes in fractured gabbros showed yields of up to 30 m³/hour. One study showed that borehole yield was directly related to the direction of tectonic structures (fracture orientation). For example, where fractures are in a NE-SW direction, yields are less than 3 m³/hour; and where fractures are in a N-S direction, yields are more than 8.5 m³/hour (United Nations, 1989).
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Groundwater status
Only limited research has been conducted concerning groundwater and no national resource estimates have been completed. However, based on the presently identified potential and the limited level of existing development, it is safe to assume that only a very small portion of national groundwater resources are being used (Groundwater Consultants Bee Pee (Pty) Ltd, SRK Consulting (Pty) Ltd, 2002).
Although groundwater quality it not presently monitored, it has been reported that water quality has declined in the coastal part of Namibe Province. This is most likely to be because of seawater intrusion. However, other urban and rural water supply schemes using groundwater in the coastal belt have not reported seawater intrusion (Groundwater Consultants Bee Pee (Pty) Ltd, SRK Consulting (Pty) Ltd, 2002).
Groundwater use and management
Groundwater use
A 2014 report stated that 73% of known water systems across Angola use groundwater sources, while 27% use surface water (Cowater 2014). Drilled boreholes equipped with handpumps represented 36% of all water supply systems (Cowater 2014). The use of groundwater varies across the country, with some provinces taking over 90% of their water supplies from groundwater, but most taking between 40 and 80% of water supplies from groundwater. Only three provinces took less than 20% of water supplies from groundwater (Cowater 2014).
The provincial capitals of Malange, Bengucia, Lubango and Namibe, and the urban centres of Tobwa and Lobito, rely on groundwater to a greater or lesser extent. In general, groundwater use in urban areas is concentrated in southern and coastal areas, where the climate is more arid and surface water is less available. Additionally, groundwater is being increasingly developed for local systems to augment water supplies in rapidly growing peri-urban areas, particularly Luanda (Groundwater Consultants Bee Pee (Pty) Ltd, SRK Consulting (Pty) Ltd, 2002).
Rural areas largely rely on groundwater - from drilled boreholes, hand-dug wells and springs. However, in areas where existing groundwater supply systems are no longer working or have not been developed, surface water is more widely used (Groundwater Consultants Bee Pee (Pty) Ltd, SRK Consulting (Pty) Ltd, 2002).
Another major use of groundwater is for livestock in the southern provinces. Water supply for livestock watering is coordinated by the Ministry of Agriculture, and groundwater is supplied through boreholes and wells equipped with either manual or powered submersible pumps. In a 1973 survey there were 943 boreholes and 319 wells supporting such systems. The present number is not available, but based on recent figures available from Cunene Province, where 125 out of 607 systems are functioning, the current number of operable systems is likely to be less than in 1973. However, individual farmers and ranchers also commonly construct boreholes and wells in these southern areas (Groundwater Consultants Bee Pee (Pty) Ltd, SRK Consulting (Pty) Ltd, 2002).
Groundwater management and monitoring
The National Directorate for Water (DNA) are responsible for aspects of water supply and water resources.
In 2002 there was no formal institution responsible for data collection related to groundwater. However, since 1996, DNA have carried out annual field surveys of the operational status of water supply systems, including boreholes and hand-dug wells, to assess the level of water supply coverage. During these field campaigns, data collected includes the location of boreholes and hand-dug wells; the number of users of each borehole or well; the borehole/well depth; the rest water level; the type and mark of pump; the name of a responsible person; and the maintenance record over the previous year. This field information is kept in paper form in the DNA archive for future use, and used to compile annual reports summarising the total number of water point sources by province and a summary of their operational status. In 2002 there were records of over 3600 groundwater points (Groundwater Consultants Bee Pee (Pty) Ltd, SRK Consulting (Pty) Ltd, 2002).
Another institution collecting data related to groundwater is the company Hidromina, which maintains a digital database with basic information generated by boreholes they have drilled. In 2002, this database held records of over 2500 boreholes (Groundwater Consultants Bee Pee (Pty) Ltd, SRK Consulting (Pty) Ltd, 2002).
General information on groundwater management in Angola may be available via the SADC Groundwater Management Institute .
Transboundary aquifers
Angola shares a number of aquifers with other countries. These include (Altchenko and Vilholth, 2013):
- the Northern Kalahari/Karoo Basin, shared with Botswana, Namibia and Zambia
- Cuvelai–Etosha Basin, shared with Namibia
- the Coastal Sedimentary Basin (Cunene River) aquifer, shared with Namibia
- the Lower Congo Precambrian Dolomite aquifer and the Congo River Coastal Sedimentary aquifer, both shared with the Democratic Republic of the Congo.
For further general information about transboundary aquifers, see the Transboundary aquifers resources page
References
The following provide more information on the geology and hydrogeology of Angola. Many of these, and others, can be accessed through the Africa Groundwater Literature Archive
Online resources
SADC Groundwater Information Portal
General information on surface water and groundwater resources in SADC
Documents
Altchenko, Y, and Vilholth, K G. 2013. Transboundary aquifer mapping and management in Africa: a harmonised approach. Hydrogeology Journal, Vol.21, Issue 7, 1497–1517.
Cowater. 2012. Development of a Comprehensive National Rural Water Supply and Sanitation Program: Phase 1 Report (Draft). Submitted to National Directorate of Water Supply, Government of Angola, by Cowater International Inc, September 2012.
Cowater. 2014. Development of a Comprehensive National Rural Water Supply and Sanitation Program: Phase 2 Report (Draft). Submitted to National Directorate of Water Supply, Government of Angola, by Cowater International Inc, October 2014.
Groundwater Consultants Bee Pee (Pty) Ltd, SRK Consulting (Pty) Ltd. 2002. Compilation of the hydrogeological map atlas for the SADC region: Situation Analysis Report Annex A - Angola. SADC Water Sector Coordinating Unit.
Hidroprojecto Consultores de Hidraulica e Salubridade SA. 1990. Mapa Hidrogeologico de Angola. Scale 1:1,500,000. Lisboa & MacDonald & Partners Ltd Cambridge.
SADC. SADC Hydrogeological Mapping Procedures and Guidelines. Technical report to the Southern African Development Community (SADC) and Cooperating Partners. European Union and GTZ.
SADC. 2009. Explanatory Brochure for the South African Development Community (SADC) Hydrogeological Map & Atlas. Technical Assistance to the Southern African Development Community (SADC). SADC Hydrogeological Mapping Project, 31 March 2009. European Union and GTZ.
United Nations. 1989. Groundwater in Eastern, Central and Southern Africa: Angola. United Nations Department of Technical Cooperation for Development, Natural Resources/Water Series, No.19, ST/TCD/6.
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