Surface water-groundwater exchange in transitional coastal environments
by airborne electromagnetics: The Venice Lagoon example
A. Paris, S. Venturini
Technital S.p.A., Verona, Italy
P. Teatini, G. Gambolati
Dept. Mathematical Methods and Models for Scientific
Applications, University of Padova, Padova, Italy
A. G. Bernstein
Consorzio Venezia Nuova, Venice, Italy
ABSTRACT
To prevent erosion of polluted land and discharge of contaminated
groundwater and surface water into the Venice Lagoon a 57 km long
cut-off wall has been designed by the Venice Water Authority and
is currently under construction along the canal banks of the Venice
industrial harbour. To predict the impact on the hydrologic regime
and mitigate the related inundation hazard in the nearby urban areas
a complex three-dimensional (3D) finite element (FE) model has been
developed and implemented over the multiaquifer system down to a
depth significantly larger than the wall bottom. The model is
initially calibrated against the regional piezometry and then
refined locally to reproduce the groundwater volume drained along
a 5 km long bank of a harbour canal already bounded. Major results
from the simulations show that after the wall completion the
subsurface discharge into the lagoon is successfully abated by as
much as 85% relative to the pre-existing rate with, however, an
expected 1 m increase of the water table in the inland city of
Mestre thus pointing to the need for implementing a drainage trench
upstream the wall to properly reduce the raised groundwater level.
The model would also indicate that the shallowest aquifers may receive
underground water from a large number of old deeper boreholes abandoned
in the past and not properly sealed. From a more general perspective
the present study constitutes an important example where the reliable
and sustainable design of a complex engineered structure bound to
impact significantly on the surrounding environment can be much helped
and improved by the use of advanced numerical models capable to capture
the essential features of the underlying geo-hydrological processes.
