STUDY AND MONITORING OF SALT WATER INTRUSION IN THE COASTAL AREA BETWEEN MAZARA DEL VALLO AND MARSALA (SOUTH-WESTERN SICILY)

In this chapter the study of a coastal aquifer located in South-Western Sicily (between the towns of Marsala and Mazara del Vallo) is presented, carried out using geochemical, hydro-geological and geophysical techniques. The aquifer has been over-exploited to the point of being subject to intense and worrisome salt-water intrusion. A preliminary chemical and physical characterization of the waters was carried out; this included measuring their conductivity and their chloride content. This allowed to detect the marine intrusion wedge in the coastal aquifer. A series of electromagnetic soundings, suitably calibrated by well logs, were effected in the whole area and allowed to create a 3D interpretative model of the resistivity distribution in the aquifer, thereby enabling to recognize the main intrusion directions and the pattern of the aquifer bed. Furthermore an integrated geophysical 2D section was carried out along a line roughly perpendicular to the coast, in one of the zones that is particularly involved in the intrusion phenomenon. Field measures included ERT, IP, TDEM and seismic soundings, all of which were aimed at reconstructing a highly detailed geophysical section. The seismic soundings clearly show the lateral variation between the fresh and salt water, such as the overburden and the clayey bed of the aquifer. The final target of this research is to propose an optimized management-model of underground resources. The lessons drawn from the use of different techniques for defining geophysical profiles suggest an integrated methodology to identify in detail the sea intrusion zone in aquifers. Therefore, the methodology used can be suitably extended and exported for studing and monitoring many similar Mediterranean coastal areas