ISOSCAPE FOR GROUNDWATER RECHARGE ASSESSMENT OF THE CONTINENTAL TERMINAL SHALLOW AQUIFER OF THE TOGO COASTAL SEDIMENTARY BASIN
Résumé
In the Coastal Sedimentary Basin (CSB) of Togo, the shallow aquifer of the Continental Terminal (CT) is the most stressed water resource despite the continuous degradation of its quality. To be able to discuss the sources of groundwater degradation in this aquifer, knowledge of the origins of the waters that contributes to its renewal is very important. This study proposes to use the stable isotopes of rainwater, surface water and aquifers to understand the recharge of the CT aquifer. Using a d 18 O-d 2 H diagram, the groundwater representative points are aligned around or below the local meteoric line of slope 7.3. This suggests that this aquifer is recharged by precipitation from oceanic origin and evaporated waters. The isoscape map of the CT waters revealed an enrichment of the isotopic signature from south to the north. The enriched signatures of the waters of the northern sector of the CT and those depleted in the southern sector are aligned on straight lines with the same slope of 4.9, thus revealing the same conditions of groundwater recharge with contribution of surface water.
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