The hydrodynamics of the Orbetello Lagoon. Measurements and numerical simulations.

In this work the hydrodynamics of the Orbetello lagoon was studied by field measurements and numerical simulations. The lagoon is a semi-enclosed coastal basin, located in the southern part of the Tuscan coast (Italy), that exchanges water with the Thyrrenian Sea by three narrow long channels. The lagoon is characterized by very shallow water of depth about 1 m and poor hydrodynamic activity. Algal blooms and anoxic crises often occur during summer months, causing problems for the water quality. In order to study and understand the inner dynamics of the lagoon, a system of gauges, collecting hydrodynamic parameters at different locations, was realized. These experimental data were used to prescribe the boundary conditions and to check the results from two different numerical models, based on the shallow water equations: the finite element model SHYFEM, developed at ISMAR-CNR in Venice, and the finite difference model MIKE21, developed at the Danish Hydraulic Institute. The use of the two models permit to compare and check the results in order to have more accuracy. By means of numerical simulations, the whole hydrodynamics inside the Orbetello lagoon was obtained. Analysis of field measurements and numerical simulations are reported.