Coastal zones are strategic areas for economic development and therefore densely populated areas.
It is estimated that about half of the world population is living in coastal areas and this percentage is
expected to rise in the future. This situation puts our groundwater resources under pressure.
Indeed, a natural equilibrium exists between fresh (potentially drinking) water and seawater in
coastal aquifers. Seawater tends to flow inland due to its higher density, while freshwater
discharges in the sea. However, human activities directly (through the extraction of groundwater)
and indirectly (through sea level rise due to climate change) alter this equilibrium. Understanding
the current state of salinity in coastal aquifers is a prerequisite for the sustainable use of
groundwater resources. In this project, we image the interface between fresh and saltwater using
their contrast in electrical conductivity. We use imaging techniques similar to medical imaging to
characterize the subsurface properties. In short, we are doctors whose patient is the Earth interior.
Part of the freshwater discharging below the low-tide line, we propose an innovative combination of
onshore and offshore electrical resistivity surveys to achieve this objective. This characterization will
enable us to better understand the fresh/saltwater equilibrium to propose future management
plans of our aquifers.