Contribution of electrical prospecting to the aquifer characterization in El Mouazir-Matmata Nouvelle in Southern Gabes, Southeastern Tunisia

The governorate of Gabes is an important economic pole in the southeast of Tunisia. However, the water shortage resulting from the succession of many periods of drought and the scarcity of surface water have significantly affected the various industrial, tourist, and agricultural activities in this region. The exploitation of groundwater has been the solution to remedy this situation. Unfortunately, the anarchic implantation of water borehole at variable depths has led to continuous decreases of their static levels and a degradation of their water quality. This is due to a lack of precise knowledge of the characteristics of the exploited aquifers despite the few studies carried out in this sense. In this context, a multidisciplinary approach combining geological, hydrogeological, and geophysical data was conducted to assess the water potential of the El Mouazir-Matmata Nouvelle area (South of Gabes). The synthesis of hydrogeological data has highlighted four sedimentary levels likely to constitute aquifers with different water potentialities. These are, from top to bottom, the Mio-Plio-Quaternary filling (MPQ) with low water potential, the carbonate series of the Lower Senonian (SIC), the carbonate bars of the marno-gypseousseries of the Lower Senonian (SIMG) and the Turonian carbonates (TUR). Unfortunately, the spatial distribution of the water borehole did not allow accurate tracking of these aquifer levels either laterally or vertically across the study area. The geophysical data represented by one hundred and twenty-five Vertical Electrical Soundings (125 VES) were of paramount importance to complete and refine the previous knowledge on the characteristics of the said aquifers. Indeed, the qualitative and quantitative interpretations of the VES have led to a relatively accurate structural model showing that the study area is compartmentalized into high zones (Horsts) and low zones (Grabens) resulting from the main NE-SW and NW–SE fault sets. The characteristics of the different aquifers levels are closely related to the type of structure considered. To this effect, the main aquifer level (SIC) is preserved in the grabens and partially or totally eroded in the horsts. Thus and in the light of the results of this study, a structural map was established and areas favorable to the exploitation of the various aquifers of good quality in a rational way were delimited.