Characterization of coastal aquifer in Sardinia affected by saltwater intrusion using a multiple approach supported by airborne electromagnetic and magnetic data collection.

Coastal aquifer salinization is a critical environmental concern arising from various factors, posing substantial threats to water resources and ecosystems. In-depth geological and hydrogeological surveys, complemented by a geochemical and isotopic approach, offer insights into aquifer physical properties, recharge areas, and salinization processes. Nevertheless, stratigraphic information in depth is often specific to a point and requires interpretation for upscaling. Reconstructing geological settings in three dimensions in coastal alluvial environments is complex due to non-linear transgressive and regressive depositional dynamics. Extensive and dense geophysical measurements in coastal catchment impacted by saltwater intrusion and groundwater can enhance hydrogeological models for improved resource management under anthropic and climate stresses. This information aids in characterizing aquifers, identifying potential vulnerabilities, and developing targeted management strategies. The coastal area of the Flumendosa plain in southeast Sardinia (Italy) has been selected as a pilot site. Saltwater intrusion affects it since the 1950s, caused by anthropic activities which altered the natural hydrodynamic equilibrium among groundwater, surface water, and seawater. Airborne electromagnetic and magnetic data collection aims to effectively reconstruct the complex hydrogeology of coastal aquifers. These geophysical datasets will allow, for example, the reconstruction of subsurface electrical resistivity up to approximately 100 meters deep, with a resolution that can be a few tens of meters in shallow portions. The geophysical model can serve as a reliable foundation for the (hydro)geological model used for scenario analysis. Effective management and prevention of coastal aquifer salinization heavily depend on a thorough understanding of geological and hydrogeological dynamics. Integrating this knowledge into mitigation strategies ensures a more accurate and tailored approach to safeguarding water resources. Given ongoing anthropogenic stresses and climate change impacts on coastal aquifers, prioritizing geological and hydrogeological research is paramount for sustainable water management.