Integrated coastal groundwater resource management: Hydrogeological modeling and early warning systems for saltwater intrusion mitigation

This research aims to provide a characterization of the hydrogeological model using geophysical techniques and numerical modeling with the implementation of an early warning system. The study area is the coastal plain of Muravera, characterized by a significant phenomenon of saltwater intrusion. The study area is the coastal plain of Muravera, affected by a marked saltwater intrusion. This phenomenon has caused environmental and socio-economic impacts, severely limiting traditional citrus cultivation across much of the plain. To reconstruct the complex hydrogeology of these coastal aquifers, recent airborne electromagnetic (AEM) surveys were performed in the region. By mapping subsurface electrical resistivity down to approximately 100 meters, the resulting data provides important information for hydrogeological model development and subsequent scenario analyses, offering valuable insights into the aquifer's structure and salinization patterns. Numerical simulation of the coupled effects of groundwater density and solute transport was performed using the iMOD-WQ code (Deltares), which integrates the well-established SEAWAT package for modeling density-dependent freshwater/saltwater interactions. Although iMOD features a graphical user interface, Python scripting was selected for model implementation due to its advanced data manipulation capabilities. Furthermore, the USGS-implemented Soil Water Balance (SWB) code was used to quantify the impact of climate change on natural recharge. This enabled the simulation of recharge variation across both spatial and temporal scales. One strategic piezometer, where continuous data loggers can be set up to measure conductivity and groundwater level, together with five additional piezometers (monitoring groundwater level only), was selected for the monitoring and implementation of an early warning system for saltwater intrusion and drought. In conjunction with this, testing is underway on the interface-egg—a new tool whose weight is calibrated to float at the specific conductivity-density of the water, to be used as an alarm threshold. The approach used has made it possible to develop a comprehensive and robust model that can inform the implementation of artificial recharge, optimize withdrawal management, and generally enhance the overall management of water resources in the study area. Strategically placed data loggers allow for continuous, comprehensive water resource monitoring, which enables the system to function as an early warning tool, particularly in the event of drought.