Africa's chronic shortage of fresh water could be alleviated by stepping up efforts to access groundwater reserves, or aquifers. UK scientists have produced a pan-African map of reserves that are found deep underground.
DW spoke to Alan MacDonald, Chief Hydrogeologist at the British Geological Survey. He led the two-year study, which also involved experts from University College London.
DW: Where are the largest groundwater reserves in Africa?
Alan MacDonald: The largest reserves are in North Africa, under the Sahara desert. That's been known about for a number of years. But they are far from where most people live. So, the reserves I'm most interested in are the smaller ones, away from there, under the rest of Africa, sub-Saharan Africa, where most of the population are without access to clean water.
What countries specifically do we find these reserves in?
The largest groundwater reserves are in North Africa, so under Libya, Algeria, Sudan and Egypt. These large, sandstone aquifers are several hundred meters thick. Some of them are exploited at the moment, for example in Libya. But the issue with these large groundwater reserves is that they were filled up with rainwater 5,000 years ago, so they are not currently being recharged. It's what we call fossil water. It was laid down…when the climate was much wetter there.
We have known about groundwater reservoirs for some time, what's new about this map and how did you produce it?
What we've done over the last two years, funded by the UK Department of International Development, is pool together all the existing maps of Africa for different countries and areas, and also 300 aquifer studies from across Africa. We analyzed them and pulled together this one map, which documents for the first time how much groundwater there is and also how easy it is to extract that water, to drill a borehole and to get water supply from the groundwater.
Access to some of these aquifers is limited. How can these reserves be tapped in a sustainable way?
What you find is when you drill a borehole, you might not get very large yields of water but, crucially, you often get enough for a borehole and a hand pump. So these groundwater reserves across Africa are sufficient for community boreholes 50 to 100 meters deep, equipped with a hand pump. Which is good news for those who don't have access to water at the moment, there are 300 million who don't have access.
So, with careful investigation and proper siting and construction of these boreholes they should be able to find groundwater. But for larger yields of water, it's much more problematic to access it, for example if people want to do large-scale commercial irrigation, which requires a lot of water they wouldn't be able to drill everywhere in Africa. There are issues with sustainability, too, if you're pulling out large amounts of water and it's not actively being recharged, then that water will run out.
What are your practical suggestions for governments, NGOs and aid organizations?
Firstly, it's acknowledging that the groundwater is there and that, realizing that for much of Africa, water resources are available for community boreholes and hand pumps…The other message would be to be careful about investing in large-scale irrigation or even city supplies that rely on having high-yielding boreholes and wells and make sure that there are sufficient investigations carried out before they do that…to find out if it's going to be sustainable.
Can these reservoirs solve Africa's fresh water problem? How much can you as a scientist help with the problem and how much of it is logistical and political?
Having the water resources alone will not solve any of the water supply problems…It's about finding the money and investment to drill the boreholes. It's also a lot about sustainability. At the moment even the boreholes that have been drilled, about a third of them are not working…So, there are wider issues. But what we've done in our research is to show for many areas, water resources is not the main issue, groundwater resources are likely to be there for many areas, not for all areas but for many, if you look sufficiently well, you'll find some groundwater resources.
Interview: Nicole Goebel
Editor: Nathan Witkop