Hydrogeology Maps Of Africa

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Please cite page as: Africa Groundwater Atlas. 2019. Groundwater and Hydrogeological Maps of Africa. British Geological Survey. Accessed [date you accessed the information]. Weblink.

These pages summarise the history and current status of hydrogeological mapping and groundwater maps in Africa. Here you will find lists of known maps, and summary information on the main groundwater maps at continental, regional and national scales.

A brief history and overview of groundwater mapping in Africa

Many maps have been produced over the years that show aspects of the hydrogeology and groundwater resources of Africa. These maps are at different scales - covering areas from a single small river catchment or local aquifer up to the entire continent - and they were designed for different uses. Not all groundwater maps are suitable for all activities: for example, some are useful for a broad overview of groundwater resources for planning water supplies; some for detailed on-the-ground borehole siting; and some for predicting and managing groundwater quality.

Hydrogeological maps began to be developed in earnest in the 20th century. An increasing demand for water in the early part of the 20th century led to a drive for more strategic planning of water resources in many countries. Hydrogeological maps were a useful tool in these efforts. The development of hydrogeological maps, at various scales and for various purposes, began in many industrialised countries around 1940 (Gilbrich and Struckmeier, 2014). In Africa, the earliest groundwater maps were published in the late 1950s.

=Overview

National scale hydrogeological maps are often seen as the minimum level of detail needed for effective planning and management, including monitoring, of groundwater resources and water supply interventions in individual countries.

National hydrogeological maps in Africa are usually at large scales of between 1:250,000 and 1:1 million, depending on the size of the country. In small countries maps can be very large scale, such as Mauritius at 1:50,000; while large countries may have smaller scale national maps, such as South Africa at 1:2,000,000 or 1:2,500,000.

National hydrogeological maps can be used to identify potentially favourable aquifers that are likely to be able to support high yielding groundwater boreholes for large scale irrigation or municipal use; or areas where groundwater is more vulnerable to over-abstraction or drought and therefore needs additional protection. They can also be useful in selecting appropriate technologies for groundwater exploitation, such as deep borehole drilling, or manual drilling. Information from hydrogeological maps at these scales can be combined with data from national groundwater monitoring, such as groundwater level fluctuations or groundwater chemistry, to support water resource management. Some countries have thematic groundwater maps, which show groundwater vulnerability to contamination, or areas of known geogenic contamination (e.g. naturally present fluoride or arsenic), nitrate contamination related to land use, or salinity related to sea water intrusion.

Today, most countries in Africa have a national hydrogeological or groundwater-focussed map. However, many of these maps are decades old, and there is much scope for updating them with more recent hydrogeological data and understanding. In most countries, national hydrogeological maps were made in the pre-GIS, or even pre-computer, era, and in most cases only hard copy maps are available - at present, few countries have digitally available hydrogeological maps. Even if not updated with new information, there is scope for digitising and georeferencing existing hard copy maps to make them compatible with GIS software, which is increasingly used for resource and environmental assessment and analysis. Finally, some countries still do not have a national hydrogeological map, even where they rely significantly on groundwater resources: the development of such a map would be a significant boost to their ability to effectively plan and manage national water resources.

History

In Africa, the earliest published national groundwater maps date from the late 1950s and 1960s. Most were developed as the basis for national water resource planning, and i they were usually developed by national government agencies – in particular, geological surveys and water resource ministries – sometimes in partnership with international aid agencies, engineering firms, or European geological surveys, in particular BRGM, BGS or BGR, or in some cases the USGS.

The earliest national groundwater maps in Africa included Madagascar in 1957; a map covering the Belgian colonial territories Congo Belge & Ruanda-Urundi (now the Democratic Republic of Congo, Rwanda and Burundi), also in 1957; Niger and Libya in 1964; and Chad in 1969.

From the 1970s to the 1990s, national hydrogeological or groundwater resources maps were published for at least another 27 countries in Africa. These were at various scales, depending on the size of the country and availability of groundwater data, and to various designs and methodologies.

In the 2000s, some countries updated their existing hydrogeological maps, including South Africa and Namibia. Since 2010, other countries have had national groundwater / hydrogeological mapping programmes that are developing new or revised hydrogeological maps at higher resolution for selected areas within the country, with an ultimate aim to produce a complete national coverage - for example, Chad, Uganda and Ethiopia. This may also include the development of new national-scale hydrogeological maps.

In 2019, the Africa Groundwater Atlas released simple overview Country Hydrogeology Maps for 38 countries in Africa, available as downloadable digital GIS files. These are based on existing large scale mapping and information, and are at a nominal scale of 1:5,000,000.

Sub national groundwater maps of Africa

Many sub national groundwater maps have been developed over recent decades in Africa, for many different purposes. National maps are not usually detailed enough to directly support the village- or town-level design, siting and development of new abstraction boreholes, and sub-national maps are needed to support national water resource management. Other maps cover specific water catchments or aquifers that are of particular significance, perhaps because of high groundwater potential, ecological sensitivity, or because an aquifer is shared with neighbouring countries (transboundary) and there are political sensitivities. Sub national maps have often been particularly developed in countries where there has been strong economic and/or political drivers for the development of groundwater resources (such as for large scale irrigation or mining), and which had the economic resources to do so. The purpose, mapping techniques and design of maps depends very much on the country and projects involved.

Sub-national groundwater maps in Africa tend to be at large scales of 1:250,000 scale or more, but the scale depends very much on the area covered by the map. In some countries, regularly spaced map sheets have been produced to cover the whole country. For example, a series of 21 ‘general hydrogeological maps’ at 1:500,000 scale covering South Africa, available from the Department of Water and Sanitation; and a series of hydrogeological maps also at 1:500,000 scale that are so far available for all of north and east Chad and will eventually be available for the rest of the country (ResEau 2021). In other countries, maps have been developed to cover administrative areas, such as a series produced by the Groundwater Mapping Programme of Uganda, which aimed to develop maps for each administrative district at scales of around 1:175,000 (e.g. MWE 2012). In some countries, maps at sub-national scale have been produced for selected key areas. In Chad, again, more detailed hydrogeological maps at 1:200,000 scale are being produced for specific important areas (ResEau 2021). In Ethiopia, a recent project has produced groundwater suitability and hydrogeological maps for selected kebeles and woredas (administrative districts) in semi-arid areas (GW4E 2020).

Many other sub-national groundwater maps have been produced for specific projects across Africa. These maps are often only available as images within project reports, and were never designed for, or released as, stand-alone maps, either hard copy or digital. An example of a map covering a specific aquifer that is available as a stand alone product is a digital map of the Ramotswa transboundary aquifer in parts of Botswana and South Africa, which is available to view in the SADC GMI online portal. There are too many sub-national groundwater maps within project reports to include all in this review. A selected few are shown in the list of groundwater maps in Africa.

Regional scale hydrogeological maps of Africa

Overview

Regional groundwater maps allow a consistent regional overview of groundwater resource. They do not simply combine individual country maps, which were made by different organisations at different times using different approaches, but harmonise existing maps and data using a consistent methodology. The earliest regional groundwater maps in Africa were produced as traditional paper maps. Regional maps produced after about 2000, began to use digital techniques, including the SADC hydrogeological map (2010), which was designed from the start for use in interactive online viewing software.

Maps covering large regions, such as north Africa or the SADC region, are usually at scales of between 1:1 million and 1:5 million.

Today, there is an increasing demand for regional hydrogeological maps in Africa, to support regional cooperation, such as relating to transboundary aquifers (TBAs) or integrated water resource management (IWRM) by Lake and River Basin Organisations.

History

A number of regional scale hydrogeological maps were published from the 1970s onwards. Most cover regions with shared political and/or economic interests, such as the regional economic communities SADC and ECOWAS, or the Arab region. They include a planning map for the exploitation of groundwater in Sudano-Sahelian Africa (1976); a map showing groundwater resource potential of West and Central Africa (1986); and a hydrogeological map of the Arab region and adjacent areas (1988).

Continental scale hydrogeological maps of Africa

Overview

Africa-wide groundwater maps provide consistent, harmonised information on aquifers and groundwater resources across the entire continent. They can support high-level overviews, development and management of groundwater resources; capture continental trends; and inform policy development at the Pan-African level. For example, they may show which regions are more vulnerable to water scarcity and need more water supply interventions, or where there are particular water quality issues with potential implications for human health.

Continental groundwater maps of Africa are usually at small scales of 1:5 million to 1:10 million or more. They show the general location and characteristics of aquifers and non-aquifers, subdivided into broad classifications. In some cases, they include generalised information on other aspects of hydrogeology, such as estimated recharge.

Most were developed as traditional paper maps (some later provided as high resolution digital pdf files), and based on hydrogeological characterisation of geological units, with ornaments or overlays showing rainfall or estimated recharge distribution and in most cases various other groundwater features. More recent continental maps, from about 2000 onwards, used digital techniques in their development, usually GIS, although they were not necessarily made available digitally. The most recent maps were designed entirely in GIS and for use in GIS. Some of these are available to view in digital online viewing software, and in some cases to download as digital files for use in GIS.

History

The first Africa-wide groundwater maps were developed in the 1980s, including a map of major hydrogeological formations of Africa overseen by the United Nations in 1988, at a scale of c. 1:20 million, and the International Hydrogeological Map of Africa / Carte Hydrogeologique Internationale de l’Afrique, overseen by AOCRS/OACT from 1988-1992, at a scale of 1:5 million. These were large collaborative projects involving many institutions in many African countries.

Two key new maps were published in 2008. The Carte hydrogéologique de l’Afrique / Hydrogeological Map of Africa, at a scale of 1:10 million, was produced by BRGM. It was developed by combining two categories of data: groundwater reservoir (or aquifer) type; and the proportion of precipitation available to recharge to aquifers. BRGM used extensive data to develop the map, which distinguishes eleven major hydrographic units. The map is produced as a hard copy available through BRGM, although it used digital / GIS technology in its development. The Groundwater Resources Map of Africa, at a scale of 1:12.5 million, was produced by WHYMAP (BGR/UNESCO) in 2008 and re-issued in 2018. It provides a planning tool for groundwater resources, and is freely available to download as a poster in pdf or image file format; the poster also shows hydrogeological sections of regional aquifers. The map can also be viewed online in the IGRAC Groundwater Resources in Africa portal.

In 2012, quantitative groundwater maps of Africa (aquifer productivity, groundwater storage and depth to groundwater level) were produced by BGS at a scale of c.1:20 million.

List of Groundwater and Hydrogeological Maps in Africa

This table provides a summary of known maps that describe aspects of the hydrogeology or groundwater resources in Africa. It is not comprehensive but includes most of the continental, regional and national scale maps, and many at sub-national scale.

The table includes information on: the map scale; publication date; publishing organisation; editors; format and links to more information.

Many of the listed maps can be viewed online and sometimes downloaded as scanned images; some can be viewed in interactive online map portals; and some are also available to download as digital files that can be used in GIS.

  Access the list of groundwater maps in Africa.

References

Gilbrich, W H, and Struckmeier, W F. 2014. 50 Years of Hydro(geo)logical Mapping Activities. German Federal Institute for Geosciences and Natural Resources (BGR) and UNESCO International Hydrological Programme (UNESCO-IHP). GW4E. 2020. MWE. 2012 ResEau. 2021. MacDonald, A M, Bonsor, H C, Ó Dochartaigh, B É, and Taylor, R G. 2012. Quantitative maps of groundwater resources in Africa. Environmental Research Letters, 7 (2), 024009. 10.1088/1748-9326/7/2/024009 MacDonald, A M, Ó Dochartaigh, B É, Bonsor, H C, Davies, J, and Key, R. 2010. Developing quantitative aquifer maps for Africa. British Geological Survey Internal Report, IR/10/103

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