A team of U.K. researchers have created what they say is the most detailed map available of groundwater for the African continent and, in the process, found there is roughly 100 times the volume of water underground than available on the surface.
The researchers, whose work was published in Environmental Research Letters, stated they hope that by mapping the natural resource that access to water can be improved by more realistically assessing water security and stress. An estimated 300 million African residents reportedly do not have access to safe drinking water. The population continues growing, and water remains a scarce commodity.
The researchers state that, to date, there has been very little information on groundwater resources, which has resulted in groundwater storage being omitted from assessments of freshwater availability. They looked at available maps, publications, and data to create the map, which provides detailed aquifer storage data and potential borehole yields. This information can assist in promoting quantitative groundwater mapping both at the national and regional levels, say researchers.
“We estimate total groundwater storage in Africa to be 0.66 million km3 (0.36–1.75 million km3),” they stated in their paper. “Not all of this groundwater storage is available for abstraction, but the estimated volume is more than 100 times estimates of annual renewable freshwater resources on Africa.”
Their research shows that there are unevenly distributed resources, with the greatest volume of groundwater located in large sedimentary aquifers in North Africa. This includes the nations of Libya, Algeria, Egypt, and Sudan.
“The amount of storage in those basins is equivalent to 75m thickness of water across that area — it’s a huge amount,” Helen Bonsor, one of the paper’s authors, told the BBC.
“Groundwater is such an important water resource in Africa and underpins much of the drinking water supply,” said Alan MacDonald, lead author of the study, in a press release. “Appropriately sited and developed boreholes for low yielding rural water supply and hand pumps are likely to be successful and resilient to climate change.”
These aquifers are not conventionally recharged through natural processes, but are thought to have been recharged more than 5,000 years ago, when the area was much wetter.
The team, which consisted of scientists from the British Geological Survey and University College London, says this does not mean that enterprising individuals can go out and drill at will for water. Drilling boreholes to access groundwater is realistically limited to North Africa, but understanding local groundwater conditions can help in planning.
There is concern that, because some aquifers aren’t being recharged, large-scale borehole developments could rapidly deplete stores.
Bonsor said:
However, our work shows that with careful exploring and construction, there is sufficient groundwater under Africa to support low yielding water supplies for drinking and community irrigation. Even in the lowest storage aquifers in semi arid areas with currently very little rainfall, ground water is indicated to have a residence time in the ground of 20 to 70 years. […] So at present extraction rates for drinking and small scale irrigation for agriculture groundwater will provide and will continue to provide a buffer to climate variability.
“Even for those with access to improved water sources, there is growing evidence that domestic water use will need to increase substantially to help move people out of poverty,” note the researchers in their paper. “There are also concerns about per capita food production in Africa that are likely to be exacerbated by climate change. Currently only 5 percent of the arable land is irrigated and there is much discussion about increasing irrigation to help meet rising demands for food production in the context of less reliable rainfall.”
Andrew Mitchell, the United Kingdom’s secretary of state for international development, deemed this work as important, adding that it “could have a profound effect on some of the world’s poorest people, helping them become less vulnerable to drought and to adapt to the impact of climate change.”
Images by Brian Tomlinson, used under its Creative Commons license.
