Continuous vertical electrical soundings (CVES) for the geological investigation of underwater deposits beneath the lake of Candia (Turin NW Italy)

We discuss below the results of a survey conducted with the CVES method on the Lake of Candia, near the city of Turin, in north-western Italy. The main objective of the study was the characterization of the sediments of the basin, in order to define the nature, the composition, the geometry and the spatial relationships of detected geological bodies. Another aim of the survey was to try to understand the hydrogeological dynamics that govern the lake basin, in order to determine, at least qualitatively, the presence of interconnecting paths with groundwater and to locate areas in which recharge or seepage flows are concentrated. Using a Laterally Constrained Inversion (LCI) approach for the data inversion, we managed to obtain fifteen resistivity sections that cover almost the entire area of the lake. By joining and interpolating the profiles it was possible to produce a three-dimensional model of the electrical resistivity distribution below the water basin. Thanks to the study, we found the presence of coarse glacial deposits, with high resistivity values, along the southern shore of the lake. These coarse deposits, primarily consisting of gravel and pebbles mixed with a sandy matrix, could be considered as the main hydrogeological window connecting surface and underground water.