Geo-electromagnetic survey of the fresh/salt water interface in the coastal southeastern Sicily

Results of geo-electromagnetic surveys and 3D mapping of the spatial distribution of fresh/salt water interface conducted during the IAEA submarine groundwater discharge (SGD) experiment in March 2002 near the boat basin in Donnalucata in the southeastern Sicily are reported. The high-resolution geo-electromagnetic profile showed the presence of several fresh/salt water horizons with various formation resistivities of geologic media. The geo-electromagnetic data confirmed the observations made by seepage metres that in the central part of the Donnalucata boat basin high seepage rates of recirculated seawater were observed. The 3D spatial distribution of formation resistivities with depth showed a saltwater intrusion at the pier, which acts as a barrier for the transport of fresh water to the sea. The geo-electromagnetic measurements showed spatial and temporal variability of the fresh/salt water interface, as measured formation resistivities were in inverse relationship with the daily tide, showing a nonlinear transformation of the boundary of the fresh/salt water interface in the process of its spreading offshore with time.