A coupled hydrogeological and multi-isotopic approach to investigate saltwater intrusion in a coastal groundwater (Sardinia, Italy)

Saltwater intrusion is a crucial environmental issue in the Muravera coastal plain (south-eastern Sardinia). Since the early fifties, the natural hydrodynamic equilibrium between groundwater, surface-water and seawater has been deeply modified by construction of dams across the Flumendosa river and the development of agriculture, tourism and aquaculture activities along the coast. The aim of this work is to analyze the different salinization mechanisms and hydrogeological inputs in order to implement an integrated and sustainable management system aimed at slowing saltwater intrusion and, on the other hand, to meet human needs. A total of 52 points were sampled among groundwater from different aquifers and surface water. Chemical and isotope analyses of δ18OH2O e δ2HH2O were carried out. To deepen the knowledge of salinization mechanisms and water evolution, analyses of δ11B, δ87Sr, and δ3H were carry out at selected sampling sites. The monitoring of water level and fresh-salt water interface in wells has been carried out in order to provide information on the groundwater response to the water level fluctuation inducted both by withdraw and natural phenomena. Influence of the tide was also investigated. This combined approach of environmental isotopes, chemical analyses and hydrogeological indicators is expected to provide useful information about the mechanisms and geochemical processes affecting groundwater in the plain and to plan measures for the correct management and protection of water resources from saltwater intrusion.