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

Abstract

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

Overexploitation of Groundwater Resources in the Coastal Aquifer System of Argolis

“…This problem is even more pronounced in the case of coastal Mediterranean aquifers where the climatic conditions in combination with the observed global changes, have resulted in increased water demands for several uses (mainly agricultural). Overexploitation of groundwater resources in such systems is a rather typical problem for the Circum-Mediterranean, as recorded in many studies (Ahmed et al, 2013;Astaras and Oikonomidis, 2006;FAO, 1997;Garing et al, 2013;Giannoulopoulos, 2000;Melloul and Goldenberg, 1997;Polemio et al, 2009;Psychoyou et al, 2006;Stamatis et al, 2006;Trabelsi et al, 2012;Recinos et al, 2015;Gkiougkis et al, 2015;Pedreira et al, 2015;Pliakas et al, 2015).…”

Integrated geophysical survey for 3D modelling of a coastal aquifer polluted by seawater

“…; Trabelsi et al . ). To define guidelines for the management of coastal aquifers with critical characteristics, a sample study was carried out, based on the integration of geophysical techniques suitable for hydrogeological monitoring (electrical tomography and seismic and electromagnetic soundings).…”

“…Determining the pollution degree of coastal aquifers susceptible to seawater intrusion can be improved through the optimization of geophysical prospecting and monitoring procedures, aimed at the detailed geometrical reconstruction and physical characterization of the aquifer, with particular regard to the intrusion wedge (Deidda et al 2006;Khalil et al 2011;Trabelsi et al 2012). To define guidelines for the management of coastal aquifers with critical characteristics, a sample study was carried out, based on the integration of geophysical techniques suitable for hydrogeological monitoring (electrical tomography and seismic and electromagnetic soundings).…”

Time‐domain electromagnetic imaging of a clayey confining bed in a brackish environment: A case study in the Kairouan Plain Aquifer (Kelbia salt lake, Tunisia)

“…These equivalences are related not only to the electrical properties and thicknesses of the (Goldman, Gilad, Ronen, & Melloul, 1991) but also to the instrumental response of the measuring device (the turn-off time in particular), which depends on the electrical properties of the very near surface (Raiche, 1984). TDEM has been widely used in highly conductive environments for hydrogeophysical exploration, particularly in saline environments (e.g., Behroozmand et al, 2016;Chekirbane et al, 2014;Fitterman & Stewart, 1986;Goldman, Arad, Kafri, Gilad, & Melloul, 1988;Gonzales Amaya, Mårdh, & Dahlin, 2018;Guérin, Descloitres, Coudrain, Talbi, & Gallaire, 2001;Trabelsi, Mammou, Tarhouni, Piga, & Ranieri, 2013).…”