Hydrogeology of South Africa

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Africa Groundwater Atlas >> Hydrogeology by country >> Hydrogeology of South Africa

Contributers

Brighid Ó Dochartaigh, Kirsty Upton, British Geological Survey, UK

Ernst Bertram, Department of Water and Sanitation, South Africa

Kevin Pietersen, SLR Consulting (Pty) Ltd, South Africa

Tamiru Abiye, Wits University, South Africa

Please cite this page as: Ó Dochartaigh, Upton, Bertram, Pietersen & Abiye, 2016.

Bibliographic reference: Ó Dochartaigh, B.É., Upton, K., Bertram, E., Pietersen, K. & Abiye, T. 2016. Africa Groundwater Atlas: Hydrogeology of South Africa. British Geological Survey. Accessed [date you accessed the information]. http://earthwise.bgs.ac.uk/index.php/Hydrogeology_of_South_Africa

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 Terms of use for more information.

Geographical Setting

South Africa. 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 geography resource page.

General

South Africa has a coastline of more than 2,500 km. The interior of the country is dominated by a large and mostly almost flat plateau with an altitude of between 1,000 and 2,100 m, which is highest in the east. This plateau is surrounded by the Great Escarpment whose eastern and highest area is known as the Drakensberg. There is a coastal belt below the Great Escarpment. There are a number of mountain ranges.

Estimated Population in 2013* 52,980,000
Rural Population (% of total) (2013)* 36%
Total Surface Area* 1,213,090 sq km
Agricultural Land (% of total area) (2012)* 79%
Capital City Pretoria (executive); Bloemfontein (judicial); Cape Town (legislative)
Region Southern Africa
Border Countries Namibia, Botswana,Zimbabwe, Mozambique, Swaziland, Lesotho.
Annual Freshwater Withdrawal (2013)* 12.500 Million cubic metres
Annual Freshwater Withdrawal for Agriculture (2013)* 63%
Annual Freshwater Withdrawal for Domestic Use (2013)* 31%
Annual Freshwater Withdrawal for Industry (2013)* 6%
Rural Population with Access to Improved Water Source (2012)* 88%
Urban Population with Access to Improved Water Source (2012)* 99%

* Source: World Bank


Climate

South Africa's climate ranges from desert in the northwest, to subtropical in the east, but is largely temperate. Rainfall is highest - over 1,000 mm/year - on the southeast coast, falling towards the west to less than 200 mm/year in the Namib desert in the west. Temporal variations in temperature and rainfall are illustrated in the graphs below.

Koppen Geiger Climate ZonesAverage Annual PrecipitationAverage Temperature

Average monthly precipitation for South Africa showing minimum and maximum (light blue), 25th and 75th percentile (blue), and median (dark blue) rainfall Average monthly temperature for South Africa 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)

More information on average rainfall and temperature for each of the climate zones in South Africa can be seen at the South Africa 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.

Surface water

Most rivers in South Africa are perennial. The largest rivers are the Limpopo river, partially shared with Zimbabwe, and the Orange river, which flows west to the Atlantic.



Major surface water features of South Africa. Map developed from World Wildlife Fund HydroSHEDS; Digital Chart of the World drainage; and FAO Inland Water Bodies. For more information on the map development and datasets see the surface water resource page.



Soil

Soil Map of South Africa, from the European Commission Joint Research Centre: European Soil Portal. For more information on the map see the soil resource page.


Land cover

Land Cover Map of South Africa, from the European Space Agency GlobCover 2.3, 2009. For more information on the map see the land cover resource page.

Geology

This section provides a summary of the geology of South Africa. Much more detail can be found in the references listed at the bottom of this page, some of which can be accessed through the Africa Groundwater Literature Archive.

The Council for Geoscience has a GeoPortal in which you can view a 1:1 million scale geological map of South Africa.

The following general geological environments are seen in South Africa (after Pietersen 2004):

Geological Environments
Period Brief description
Unconsolidated deposits
Quaternary - Tertiary Including Kalahari aeolian sands; and alluvial deposits in river valleys.
Sedimentary rocks
Carboniferous to Triassic Karoo Supergroup. Consists mainly of sandstone, mudstone, shale and siltstone.
Ordovician to Devonian Table Mountain Group and similar geological units. Dominantly arenitic, quartzitic sandstones.
Volcanic rocks
Including basalts of the Karoo Supergroup.
Intrusive igneous rocks
Largely granitic rocks.
Basement
Precambrian Crystalline metamorphic and igneous rocks.

Hydrogeology

This section provides a summary of the hydrogeology of the main aquifers in South Africa. More information is available in the references listed at the bottom of this page. Many of these references can be accessed through the Africa Groundwater Literature Archive.

Many hydrogeological and groundwater resource maps are available for South Africa. In particular, these include the Hydrogeological Map Series of 21 hydrogeological maps at 1:500,000 scale produced by the Department of Water and Sanitation (DWS), which covers the whole country. These show aquifer type (e.g. intergranular or fractured) and median borehole yield, with geology, rainfall and other information. These are available to purchase as hard copies from the Department of Water and Sanitation.

A hydrogeological map of South Africa at 1:2,000,000 scale, also published by DWS, is available to view on the WHYMAP website.

A SADC mapping programme produced a Regional Hydrogeological Map for the SADC region ( SADC HGM 1 2010).

The DWS produces a set of national groundwater maps including an aquifer classification map, groundwater quality map, and aquifer vulnerability map.

Summary

Most aquifers in South Africa are in fractured rock domains. Most research has focussed on the main Karoo Basin aquifer and the dolomite aquifers. There is still much to learn about the hydrogeology of many of South Africa's aquifers (Pietersen 2004).

Dominantly Unconsolidated

Named aquifers Summary
Coastal sand, gravel and other unconsolidated sediments; alluvial sand and gravel in river valleys Typically shallow and unconfined. Usually less than 30 m thick. Typical yields in alluvial deposits are 3 to 8 l/s; typical yields in coastal sands are 3 to 16 l/s (Pavelic et al. 2012). Recharge rates are generally high. The aquifers are highly vulnerable.

Sedimentary - Intergranular & Fracture Flow

Named aquifers Summary
Karoo Supergroup An important aquifer in South Africa. Typically low permeability, particularly fine grained shale, mudstone and similar layers, in which groundwater flow is largely via fractures and other discontinuities, and storage capacity is limited (Pietersen 2004). Sandstone layers typically have dual permeability and have better groundwater potential. Pavelic et al. (2012) state that overall, the Karoo forms low to moderately productive aquifers, with typical borehole yields 1 to 3 l/s.

Groundwater quality is variable. Most groundwaters have total dissolved solids (TDS) values between 450 and 1000 mg/l, with the highest values in the west and south of the basin (Pietersen 2004).

Table Mountain Group An important aquifer. Groundwater often at more than 100 m depth; evidence for hot groundwater circulation at depths of up to 2000 m (Pietersen 2004). Groundwater is usually of Na-Cl type, with low pH, low hardness and low dissolved solids (Pietersen 2004).

Sedimentary - Fracture Flow

Named aquifers Summary
Dolomite Very important, particularly in northwest South Africa. The dolomite ranges from 200 to 1900 m thick. Karstic features are developed in the dolomite and they can form high yielding aquifers. Typical borehole yields are 20 to 50 l/s (Pavelic et al. 2012). Dissolution channels developed along fractures can extend to the ground surface, allowing direct recharge and groundwater flow (Pavelic et al. 2012). Vulnerable to pollution, because of thin soil cover and high permeability with rapid fracture flow.
Volcanic rocks Little is known of the groundwater potential of these rocks.
Intrusive igneous rocks Groundwater in these rocks occurs in fractures and weathered zones, both of which are often associated with major stuctural features, such as folds and faults; or with dykes. Water-bearing features are best developed in the uppermost few tens of metres. Groundwater quality is often affected by elevated fluoride (Pietersen 2004).

Basement

Named aquifers Summary
Crystalline metamorphic and igneous rocks In these rocks, groundwater is found in the shallow weathered (regolith) zone in the uppermost few tens of metres of the rock - usually to a maximum of around 50 m depth (Pietersen 2004) - and/or in deeper fracture zones. Aquifer properties depend on the development of fractures and weathering. They generally form low productivity, local aquifers, with limited storage capacity. Borehole yields are typically low. Where they are overlain by unconsolidated aquifers, such as alluvium, groundwater in both aquifers can be hydraulically connected, increasing storage and groundwater potential.

Groundwater quality is partially controlled by the products of weathering and by length of residence time, with groundwater in shallow, active aquifers typically having lower levels of mineralisation than deeper, slower circulating aquifer systems. Groundwater is dominantly of Na-Cl type. Nitrate concentrations can be elevated due to natural factors (Pietersen 2004).

Groundwater Status

DWA (2010) reported an estimate of the total volume of available, renewable groundwater in South Africa (the Utilisable Groundwater Exploitation Potential, or UGEP) at 10,343 million m³/a (or 7 500 million m³/a under drought conditions. Current use is between 2,000 and 4,000 million m³/a of this groundwater (DWA 2010).


Groundwater use and management

Groundwater use

Current estimated groundwater use is between 2,000 and 4,000 million m³/a (DWA 2010). In most regions, groundwater is used most for rural water supply and/or irrigation. Other major users of groundwater are the mining industry and urban municipal water supplies (DWA 2010).

Groundwater management

Groundwater resources in South Africa were originally studied by the hydrogeologists of the Geological Survey, now the Council for Geosciences. The Department of Water and Sanitation (DWS), the Water Resources Commission (WRC), and to a lesser extent the Council for Scientific and Industrial Research (CSIR) have produced major studies of groundwater conditions in South Africa.

The DWS is the main implementer of the National Water Act, and through the Directorate of Surface and Groundwater Information, is responsible for, among other things, groundwater data acquisition and management and the development and maintenance of the main groundwater information systems for South Africa; carrying out regional monitoring; directing and carrying out groundwater resource assessments and exploration, including drilling; and evaluation and recommendations for water licensing.

The DWS publish many reports and other documents relating to groundwater, including water resources status reports, and guidelines and standards for the development and management of groundwater. These can be accessed through the DWS website. One of these is the Groundwater Strategy 2010 report (DWA 2010).

The DWS maintains an online National Groundwater Archive. In 2010 this contained records of about 250,000 groundwater sources (boreholes, wells, springs), including, where available, lithological, borehole construction, groundwater level and groundwater quality information. Another database, the Water Authorisation and Use database, stores information on volumes of groundwater used, based mainly on licensed volumes (DWA 2010).

Legislation

The National Water Act (Act 36 of 1998) recognised groundwater as a common asset (DWA 2010).

The National Environmental Management Act of 1998 and the Minerals and Petroleum Resources Development Act of 2002 make new legal obligations for the mining and other industries in terms of the monitoring and remediation of pollution of water resources, including groundwater (DWA 2010). Further protocols, strategies and standards are listed in DWA 2010

Groundwater monitoring

The DWS has responsibility for groundwater level and quality monitoring. DWS operates various groundwater level and quality monitoring networks and systems. Groundwater data is reported in various ways, such as quarterly National State of Water Resources Reports (e.g. DWS 2014).

Transboundary aquifers

South Africa shares a number of aquifers with other countries. These include (Altchenko and Vilholth 2013):

- the Pomfret-Vergelegen (or Khakhea/Bray) dolomite aquifer, shared with Botswana;

- the Limpopo River alluvial aquifer, shared with Zimbabwe and Mozambique;

- the South West Kalahari/Karoo aquifer, shared with Botswana and Namibia;

- the Coastal Sedimentary basin (Gariep) aquifer (Orange River Coastal), shared with Namibia;

- the Coastal Sedimentary Basin (Incomati/Maputo/Mbeluzi) and Rhyolite-Breccia (Umbaluzi basin) aquifer, shared with Mozambique;

- the Ramotswa Dolomite basin aquifer, shared with Botswana; and

- the Tuli Karoo Sub-Basin aquifer, shared with Botswana and Zimbabwe.


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 South Africa.

They, and many others, can be accessed through the Africa Groundwater Literature Archive.

The Water Research Commission (WRC) maintains the Knowledge Hub, a major online searchable archive of reports and other documents relating to water in South Africa.


Useful web resources

Department for Water Affairs and Forestry - Groundwater. https://www.dwaf.gov.za/groundwater/

Water Research Commission. http://www.wrc.org.za/

Council for Scientific and Industrial Research. http://www.csir.co.za/


Published literature

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.

Council for Geoscience. 2003. Simplified Geology of South Africa, Lesotho and Swaziland. Map compiled by CJ Vorster.

DWA. 2010. Groundwater Strategy 2010. Department of Water Affairs, South Africa.

DWS. 2014. The National State of Water Resources Quarterly Report July to September 2014. Prepared by: Directorate: Water Information Programmes; Chief Directorate: Water Information Management.

Pavelic P, Giordano M, Keraita B, Ramesh V and Rao T (eds.). 2012. Groundwater availability and use in Sub-Saharan Africa: a review of 15 countries. IWMI, Sri Lanka, 2012.

Pietersen KC. 2004. A Decision-Making Framework for Ground water Management in Arid Zones (with a Case Study in Namaqualand). Unpublished PhD thesis, University of the Western Cape.

SADC. 2010. Technical Assistance to the SADC - 'SADC Hydrogeological Mapping Project' (9 ACP RPR 39-89); Final Report. Southern African Development Community European Development Fund, HGM-1, March 2010; a technical report to the Southern African Development Community (SADC) and Cooperating Partners: European Union and GTZ.

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