METHODOLOGICAL APPROACH TO SIMULATE THE EVOLUTION SEAWATER INTRUSION WITH CLIMATE CHANGE

Seawater intrusion is a major environmental problem in coastal areas around the world, significantly contributing to the depletion of water resources. Even a small amount, less than 1% of seawater intrusion in an aquifer, can render freshwater unfit for drinking. Furthermore, locally, water quality impairment can also lead to soil degradation, limiting its use or causing land abandonment. In the framework of the Return project (founded by the Next-GenerationEU, NRRP), this paper presents a new methodology for simulating seawater intrusion, accounting for the decrease in natural recharge caused by climate change. To simulate the coupled effects of groundwater density and solute transport, this study utilizes iMOD-WQ software developed by Deltares. This software incorporates SEAWAT, a well-established tool for modeling density-dependent interactions between freshwater and saltwater in aquifers. iMOD itself is a modified version of the source code specifically designed for parallel processing. This approach significantly accelerates computations by up to two orders of magnitude, depending on the available computer resources. This efficiency is crucial, especially when simulating long time periods essential for studying climate change impacts. While iMOD offers a graphical user interface, Python scripting was chosen for this study due to its superior data manipulation capabilities. A Soil Water Balance code was used to quantify the impact of climate change on natural recharge. This code, implemented by the USGS, allows the variation of recharge to be simulated in both time and space. In addition to climate data, the code is based on soil characteristics. Four inputs are needed: land use, available water capacity, hydrological soil group and Flow direction. The area under study where this approach was applied is the coastal plain of Muravera (Sardinia, Italy), where the problem of seawater intrusion has been causing not only environmental but also socio-economic problems for more than 50 years. Thanks to a large dataset base, all the necessary inputs to the codes used are derived from measurements obtained on the field over the years. This approach can make an important contribution in water resource management by enabling the development of effective strategies to mitigate salt intrusion under anticipated climate change impacts. Its applicability to similar areas makes it a valuable tool for broader water resource protection.