Using continuous resistivity profiling (CRP) method to identify electrical resistivity variations related to FSGD areas.

The characterization of fresh submarine groundwater discharge (FSGD) in coastal aquifers has been the object of study in many investigations due to the importance of water as a strategic resource for populations. However, investigating processes that occur in the part of the aquifer located under the sea entails greater difficulties. 
The objective of this study has been to characterize FSGD in the coastal alluvial aquifer of Maresme, located 40 km north of the city of Barcelona. To study the marine part of the aquifer with good spatial resolution, the geophysical method of continuous resistivity profiling (CRP) has been chosen. Marine profiles, parallel and perpendicular to the coastline, have been done using a boat in a shallow water area to obtain electrical resistivity data of the seabed covering 3 km². Data acquisition has been carried out in two field campaigns, one in the dry season and another in the wet season. 
From the results obtained, it has been possible to observe different electrical resistivity values in marine sediments along the coast. These variations have also been identified between the two campaigns, being the wet season the one with the highest electrical resistivity values. This study shows that CRP is a non-invasive method that allows the detection of resistive zones of marine sediment that have been related to preferential discharge areas.

Acknowledgments
This work was partly funded by the Spanish Government (grant no. PID2019-110212RB-C22) and the project TerraMar (grant no. ACA210/18/00007) of the Catalan Water Agency.