Assessing water exchange between sea and the Orbetello lagoon (Italy) by field measurements and numerical simulations

This article presents an assessment of water exchange between sea and the Orbetello Lagoon, Italy. The work methodology is based both on field measurements and on numerical simulations. The assessment is related to tidal, wind and atmospheric pressure for the whole 2016, taken as exemplary year. Field measurements have been conducted by means of level gauges, installed at four internal lagoon points, and one anemometer installed at a central internal point. Moreover, two tidal gages, one located at Civitavecchia harbor and the other at Marina di Campo (Elba Island) have been used to set the offshore boundary conditions for the numerical model. The numerical simulations have been conducted with the HD FM module of the MIKE21 software package, a fully non-linear shallow water solver. The numerical results match closely the field measurements, in terms of total sea-lagoon water exchange, but the former also permits to simulate the whole lagoon hydrodynamics thus allowing much deeper understanding of this physical system. In fact, the numerical simulation has also permitted understanding of the fraction of total water exchange taking place at each of the three lagoon channels connecting the lagoon to the sea.