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New groundwater maps support African water security and adaptation to climate change

UCL Geography in international collaboration to monitor recharge

New groundwater maps support African water security and adaptation to climate change

A new study reveals that reserves of groundwater in much of the populated parts of Africa are being replenished at rates that could help to protect communities against the damaging effects of climate change and also sustain widespread groundwater pumping for drinking water.

A team of researchers from across Africa and the UK, including Professor Alan MacDonald, of the British Geological Survey (BGS), Professor Richard Taylor, of UCL Geography and Professor Seifu Kebede from the University of KwaZulu Natal, estimates that long-term groundwater recharge in Africa is approximately 15,000 km3 (cubic km) per decade, including some recharge even in arid and semi-arid areas.

In 2012, BGS and UCL scientists found that, although Africa is a notoriously dry continent, it is actually sitting on a vast reservoir of groundwater. Effective water supply investments thus require reliable data, not only about groundwater availability and storage, but also how quickly it is replenished as ‘recharge’.

Now, for the first time, the team has published maps of long-term average groundwater recharge based on ground-based measurements. The maps show average recharge rates for the whole of Africa between 1970 and 2019, comparing results from over 134 studies, combining them with data about available groundwater storage.

Published in the journal, Environmental Research Letters (ERL), the maps provide a new and unique perspective on water security for Africa. They also emphasise that groundwater recharge needs to be assessed over decades rather than individual years because of variability in the intensity of rainfall from year to year.

According to the lead author Professor Alan MacDonald of the BGS:

“The data reveal some interesting patterns about Africa’s water security. We already know that having both low groundwater storage and recharge considerably reduces water security for local populations. What these new maps tell us is that the majority of African countries have either high storage or high groundwater recharge."

Only five countries have both recharge and storage below the African average, including eSwatini, Zambia, Lesotho, Zimbabwe and Eritrea. This is where extra care is needed to develop groundwater. The maps also show, however, that many North African countries with little rainfall, such as Libya, Algeria and Egypt, usually considered to be water insecure with very low recharge rates, have considerable groundwater storage.

Co-author Professor Richard Taylor explains:

“In areas where groundwater is largely disconnected from current climate, groundwater pumping slowly depletes a finite reserve. Consequently, increased groundwater pumping in the short term could ultimately be at the expense of future generations. Conversely, most African countries with little groundwater storage, such as Liberia, Cote D’Ivoire and Burundi, receive regular recharge so we know this can form a reliable supply. Nevertheless, if groundwater is overused, for example for large scale irrigation, available groundwater could still be in danger of drying up during droughts.”

The researchers hope that the maps will provide a benchmark for assessing future models and a reliable baseline for future research.

Co-author Professor Seifu Kebede adds:

“This effort brought together extensive African knowledge with expertise from other countries to provide information to develop water resources sustainably and overcome some of the most pressing issues countries often face, such as drought, deprivation, and starvation.”

The research was funded by the UPGro research programme, co-funded by the UK Natural Environment Research Council, Foreign, Commonwealth & Development Office, and the Economic and Social Research Council.

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Recharge map: Long-Term Average (LTA) groundwater recharge for Africa, based on best linear prediction from study value observations shown, and graphed relationship between LTA groundwater recharge and LTA rainfall.


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