Assessment of potential seawater intrusion in a coastal aquifer system at Abomey - Calavi, Benin

Severe sea-water intrusion can be detected several kilometers inland and represents a high risk for coastal region groundwater. The coastal aquifer of the continental terminal of the township of Abomey-Calavi (Benin) has been highly exploited for intensive drinking water capture to supply the most important cities of Abomey-Calavi, Sèmè and Cotonou in Benin. During the past 15 years, extracted water quantities for drinking water supply to those cities rose to the point where saline intrusion was suspected. The present study aims at determining the intensity and the extent of saline intrusion, if any, in those regions. Elaboration of Piper diagrams, related graphs and Stiff diagrams resulted in the ascertainment that groundwater in the district of Godomey is probably contaminated by sea water and revealed Togbin to be an area of intrusion of seawater into groundwater. This study has helped in setting the boundaries where seawater intrusion into groundwater occurs in the township of Abomey-Calavi. These results confirm previous findings, which had detected an early saline intrusion in this Godomey pumping area.