Friday, 20 April 2012

Mapping Africa's groundwater resources.

Many parts of Africa have long struggled to find sufficient clean water to provide for the needs of their populations or for agriculture or industry. The continent also has a growing population, and is likely to suffer severe changes in rainfall patterns due to climate change in the next few decades. The continent is known to have large groundwater resources in places, but the records of these are scattered, making continent-wide studies of water resources difficult.

In a paper published in the journal Environmental Research Letters on 19 April 2012 a team of scientists lead by Alan MacDonald of the British Geological Survey produce a series of maps detailing groundwater resources across the continent, collated from a wide range of sources.

Map showing the depth of water in aquifers across Africa. Contour lines show rates of recharge. MacDonald et al. (2012).

MacDonald et al. collated data from a variety of sources including previous regional studies, governmental reports, and data from oil exploration companies. The quality of the data varies from region to region. Water resources for much of Southern Africa are very well documented, and North Africa is nearly as well studied. West and Central Africa are generally poorly known, except in Ghana and Nigeria, where there have been a number of good studies.

Maps showing the depth of the water-table bellow the surface (top), and the likely productivity of aquifers, based upon how difficult the water is likely to be to extract. MacDonald et al. (2012).

The most significant resources are found beneath the Sahara, where they could potentially be of great use. However these are ancient resources that have not been significantly replenished in the last 5000 years; if they are used then they will not be replenished, permanent plans for their use could not be made. The study does not take into account the possibility of aquifers containing contaminated water, though this is likely to be the case in places, either from natural contaminants derived from rocks, such as arsenic of fluorides, or from man-made sources such as contamination from sewers in major cities.

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