Continental and marine surficial water - groundwater interactions: the case of the
southern coastland of Venice (Italy)
L. Tosi, C. Da Lio
Institute of Marine Sciences, CNR, Venezia,
Italy
P. Teatini
Dept. of Civil, Environmental and Architectural Engineering, University of Padova, Padova, Italy
A. Menghini, A. Viezzoli
ABSTRACT
Understanding the continental-marine surficial water-groundwater exchanges in transitional
coastal environments is really challenging at large scale. It requires an image of the
saltwater-freshwater relationship which is difficult to be obtained especially in
wetlands, lagoons, and marine areas. This study is focused on the coastland of the
southern Venice lagoon - northern Po river delta (Italy), a precarious environment
subject to both natural changes and anthropogenic pressures. Here, saltwater severely
affects farmlands and aquifers. We used an airborne electromagnetics (AEM) survey with
the goal of characterizing the continental and marine surficial water-groundwater
interactions in such coastal region. The AEM survey allowed depicting a clear image
of the fresh water-saltwater occurrence in shallow aquifers along mainland-lagoon -
littoral-sea profiles, up to 20-km long. The results reveal that continental groundwater
is located in the lagoon subsoil below a 10-20 m thick saline aquifer and extends down to
70 m depth. The whole low-lying farmland located south of the lagoon margin is seriously
affected by saltwater contamination, which occurs from a few to about 50 m depth.
The integrated analysis of AEM, seismic and borehole data shows that buried morpho-geological
structures, such as paleo-channels and over-consolidated clay units control the saline
contamination from the lagoon and the sea into the coastal aquifer system.
