Finite Element Modeling of Salt water Intrusion in the Venice Aquifer System

The Venice aquifer system is threatened by the intrusion of seawater from the overlying lagoon and of fossil saltwater from the deeper formations beneath the sea. A fully coupled flow and salt transport finite element model of the Venice system for the prediction of the expected maximum extent of saltwater intrusion in a vertical section of the system is presented. We obtain a steady state solution of the coupled flow and transport problem, which provides the potential largest extent of saltwater intrusion on condition that the present piezometry does not significantly change in the future. The results show that the salt intrusion concerns a restricted area extending few km inland from the coastline. In the upper part of this zone, down to a depth of 200 m, the predicted salt concentration varies between 3.5 and 7 g/l and is mainly due to the seawater penetrating vertically from the lagoon. Below we find a higher concentration (3.5 - 14 g/l) caused by the lateral intrusion of fossil saltwater.