In coastal regions, surface water supplies are frequently limited, and groundwater is essential to handling the intricate problem of water supply. Groundwater resource management is being negatively impacted by urbanization and climate change in a number of ways, and as the population grows, so does the amount of wastewater produced. Furthermore, salinity issues and heavy urbanization are common in coastal areas. Seawater migrates inland and rises toward the wells as a result of the extensive groundwater extraction from coastal aquifers, which also lowers freshwater outflow to the sea and causes seawater intrusion The municipalities of Malgrat, Palafolls and Blanes (Barcelona province, NE Spain) are located over sedimentary detrital formations of deltaic origin that form the mouth of the Tordera River and has an hystoricalhistorical dependence of groundwater resources for water supplying. Moreover, the current monitoring network is not able to provide details about the water mixing processes due to technical con-straints (limited number of piezometers with limited depth). Electrical resistivity tomography (ERT) has proven to be effective in providing the comprehensive subsurface data needed for improving groundwater modelling. The connections between the salinity of groundwater and the electrical resistivity of the bedrock and alluvial sediments demonstrate the advantages of geophysical approaches over other, more expensive subsurface research strategies. Our study's findings demonstrate that ERT in conjunction with implicit modelling methods can yield data that is highly useful for determining aquifer geometry in the Tordera’s delta (NE of Spain) and describing the saltwater intrusion of the shallow alluvial aquifer.