Application of resistivity method (VES) to quantify the thickness of the freshwater aquifer for supply in a saltwater intrusion region: historical case in Brazil

This paper presents the use of resistivity method to quantify the thickness of the freshwater aquifer for supply in a coastal region, where saltwater intrusion is constant. The results obtained have unusual clarity and quality in the literature, being a historical case. vertical electrical sounding (VES) technique was used to determine water table and saltwater intrusion depths. Sandy sediments thicker than 120 m and smooth topography are constant, where an area of approximately 2.7 × 2.2 km with 15 well-distributed VES was studied. The area is located between Lagoa dos Patos (brackish water) and the Atlantic Ocean. The only possibility of obtaining fresh water is the exploitation of the water table with the drilling of shallow wells in places, where the freshwater layer is thicker. The VES results quantified the water level depths between 3.5 and 6.0 m and the saltwater intrusion between 12.5 and 21.0 m, obtaining the thickness of the freshwater stratum. This work also approaches considerations about the depth of investigation of the VES, showing that this depth does not depend only on the openings between the current electrodes, but also on the distribution of the geoelectric strata.