Critical stress scenarios for a coastal aquifer in southeastern Italy

Over the last years the sustainable management of coastal water resources has become strategic, especially in southern Salento Peninsula (Apulia), where mal-performing management strategies adopted, together with the vulnerability of the hydrogeological system, have given rise to the deterioration of groundwater quality due to saltwater intrusion. In the study area there is the presence of multilevel shallow aquifer and a deep aquifer that interact by means of faults. The geological system is highly vulnerable to seawater intrusion so there is the need to adopt management strategies to avoid seawater intrusion phenomena. Nevertheless there is a lack of studies that analyze the methodology for the correct exploitation if the water resource in order to avoid further intrusion phenomena. This paper combines a density-driven, flow numerical model (Seawat v.4) with a fault conceptual and hydrologic model to simulate saltwater intrusion phenomenon in the deep as well as in the shallow aquifer of the Salento area. By means of the individuation of an indicator parameter of groundwater quality, it has been possible to simulate different scenarios of exploitation and therefore to define critical stress scenarios for both aquifers. The results show that the deep aquifer is more vulnerable than the shallow one, which means that in the former, in order not to reach conditions of contamination, a lower density of wells is necessary than in the latter. The reduction of well density coupled with the artificial recharge of freshwater into the aquifer may be proposed as a solution strategy to protect the aquifer. Therefore, future developments of the present study will be represented by the simulation of different scenarios of recharging to inhibit the saltwater intrusion front further inland. The proposed methodology and its future developments can represent an empirical tool to provide preliminary guidelines for long-term groundwater management in coastal aquifers.