Delineation of saltwater intrusion zones using the time domain electromagnetic method: the Nabeul–Hammamet coastal aquifer case study (NE Tunisia)

摘要

The time domain electromagnetic method (TDEM) is applied to monitor, to delineate and to map the saltwater intrusion zones innthe Mediterranean Plio-Quaternary aquifer. Forty-two TDEM soundings were carried out in the coastal plain of Nabeul–nHammamet region (NE Tunisia). TDEM resistivity data were correlated with the existing borehole logging data to assign them tona particular lithology and to provide information about the position of the freshwater–seawater transition zone. The geoelectricnsections showing the vertical configuration of seawater intrusion, with the brackish-salty-saturated zones, have a resistivitynranging from ~0.1 to 5 Ωu0001m and are detected at a depth lower than 1.5 m. The salinized zones are located at Nabeul (Sidi Moussa,nSidi El Mahrsi, Al Gasba and Mrazgua) and at Hammamet (Touristic zone of Hammamet north and south, Baraket Essahel) andnreached a distance of 4 km from the coastline, indicating a severe state for the aquifer in these zones. These TDEM results arenconfirmed by the increase of chloride concentration content in the analysed water samples of monitoring wells. Moreover, in thennortheastern part, the presence of a saltwater front located far from the coast and along the NW–SE major surface fault can benexplained by two hypothesis: (i) this fault seems to provide a conduit for seawater to move readily towards the water wells andn(ii) the clay and gypsum infiltration of marine Messinian deposits through the fault plane leads to low resistivities. Finally, itncomes out from this study that TDEM survey has successfully depicted salinized zones of this coastal aquifer. Copyright © 2012nJohn Wiley & Sons, Ltd.