Salinization of groundwater is a major challenge for Mediterranean coastal regions. Seawater intrusion can threaten essential water resources, while understanding and predicting these processes is complicated by the diversity of geological and hydrogeological settings.

My research focuses on the mechanisms of coastal aquifer salinization, their monitoring, and the development of strategies to sustainably protect groundwater resources.

Understanding the mechanisms

In coastal aquifers, the balance between freshwater flowing towards the sea and denser seawater moving inland controls the distribution of salinity. This balance changes in response to groundwater levels, pumping and marine conditions.

Salinization mechanisms vary considerably depending on the geological setting. In coastal karst aquifers, conduits and permeability heterogeneities produce complex and dynamic salinity distributions. In multilayer aquifer systems, several aquifer units may be affected by distinct or overlapping seawater intrusions. Groundwater salinity can also result from the geological and geomorphological history of coastal regions, including the presence of former lagoons.

Distinguishing between these mechanisms is essential for assessing aquifer vulnerability and identifying appropriate protection measures.

Anticipating future changes

Climate change may increase the vulnerability of coastal aquifers through several mechanisms: reduced recharge, increased water demand and sea-level rise. Groundwater abstraction, particularly for irrigation, can also lower groundwater levels and promote seawater intrusion.

The extent of these changes depends, however, on the characteristics of each hydrogeological system. Anticipating future risks therefore requires long-term monitoring and a better understanding of groundwater flow processes.

What adaptation strategies are available?

Protecting groundwater resources first requires improved monitoring of salinity, combining hydrogeology, geophysics, coastal observations and modelling.

Groundwater abstraction management is another key approach. Reducing water consumption and adapting the location and operating conditions of pumping can help limit pressure on coastal aquifers.

Managed aquifer recharge (MAR) offers another potential solution. By locally raising groundwater levels, MAR can create a hydraulic barrier that may help repel seawater intrusion. Other measures, such as subsurface physical barriers, can also be investigated depending on local conditions.

Field sites in Occitanie, southern France

My research and the projects in which I am involved focus on several coastal areas in Occitanie, including the Narbonnaise, the Orb River, Thau Lagoon and the Roussillon Plain.

The Vise submarine spring, located in Thau Lagoon, provides an original case study for investigating interactions between a coastal karst aquifer, freshwater and seawater. Monitoring this system helps improve our understanding of flow reversals and salinization dynamics.

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