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Using Isotopic Techniques to Map and Analyse Groundwater Resources in the Sahel

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Despite a series of droughts and consistently low rainfall over the past few decades, the Sahel is home to rich bodies of water — hidden underground.

Increasing water demand resulting from population growth and the uncertainties caused by climate change and land use on water resources raise the question of how to ensure the safety and sufficiency of clean water for drinking, food production and sanitation. For a semi-arid region like the Sahel, having the right scientific tools to find out more about groundwater supplies could mean long-term access to clean water.

Through an IAEA technical cooperation project that began in 2012, scientists from Algeria, Benin, Burkina Faso, Cameroon, the Central African Republic, Chad, Ghana, Mali, Mauritania, Niger, Nigeria, Senegal and Togo were trained in water sampling for isotope analysis in order to carry out a detailed survey of groundwater supplies. The project covered parts of five major transboundary aquifer systems in the area: the Iullemeden Aquifer System, the Liptako-Gourma-Upper Volta System, the Senegalo-Mauritanian Basin, the Lake Chad Basin and the Taoudeni Basin.

Over 2000 water samples were collected from different aquifers over a four-year period during both the dry and humid seasons.

“By using isotopic and chemical tracers, scientists were able to collect important information on the origin, flow patterns, residence time and renewal rate of groundwater,” said Kamel Zouari, Professor and Laboratory Head at the National Engineering School of Sfax, Tunisia, who worked on the project. “Scientists also determined the hydraulic interactions between shallow and deep aquifers and between aquifers and surface water. This information has been compiled in a dedicated database for each basin.” To learn more about the techniques used, see Isotope hydrology: an overview.

These research activities led to the creation of the first broad overview of groundwater in the Sahel, covering an area of five million square kilometres. “In general, the aquifer systems located in the different shared basins represent a significant reserve of good quality water to cover most human needs,” said Zouari.

In general, the aquifer systems located in the different shared basins represent a significant reserve of good quality water to cover most human needs.

Kamel Zouari, Professor and Laboratory Head, National Engineering School of Sfax, Tunisia