The role of the morpho‐hydro‐geologic setting of the Venice coastland in the salt‐freshwater and surface water‐groundwater exchange

DA LIO C.; TOSI L.; CAROL E.; VIEZZOLI A.; MENGHINI A.; TEATINI P.

Londres

Congreso; ECSA 55 Unbounded boundaries and shifting baselines: Estuaries and coastal seas in a rapidly changing world; 2015

Since the 16th century, human interventions in the Venice coastland (Italy) triggered significant changes on the morpho-hydrologic processes leading to a progressive shifting of the groundwater-surface water exchanges from natural- to anthropogenic-driven. In the present coastal landscape, which is characterized by large reclaimed farmlands, saltwater contamination is one of the hazard mostly jeopardizing the agricultural activities. Because of the complexity of the coastal transitional zone, a simultaneous survey of the continental-marine groundwater and surface water and groundwater interactions is challenging. In order to overcome the logistical problem of the land-based measurements, an airborne electromagnetics (AEM) survey has been carried out to record tens of km-long resistivity sections crossing lagoons, farmlands, and watercourses in a continuous like-simultaneous acquisition. The AEM data, appropriately calibrated and validated with in-situ measurements, have allowed to outline the surface water-groundwater exchange and the salinity distribution in the aquifers down to 100-150 m. This work points out the role of the morpho-hydro-geologic setting of the coastland between the Venice Lagoon and Po River Delta in the salt-freshwater and surface water-groundwater interaction. Results clearly show that saltwater intrudes into the coastal farmland from the Adriatic Sea and the lagoons. However, coastal dunes, watercourses, lowlands, and buried geomorphological structures (e.g., sandy paleochannels and ancient coastlines) significantly influence the surface water-groundwater exchanges and the saline distribution in the farmlands. Specific mitigation strategies, such as mobile gates at the main river mouths, artificial aquifer recharge through sandy paleochannels, and real-time control pumping stations are under planning and testing.