Studio idraulico delle correnti e della salinità in uno stagno costiero

Environmental monitoring and a study of the tidal cur-rents was carried out on a coastal lagoon in a wetland area of Northern Sardinia. This was done as part of a research project to exploit the fish resources in an ecologically compatible way. The relative shallowness of the lagoon in relationship to its surface area allows to use a two-dimensional depth-averaged hydrodynamic and diffusive model. The coupling of the alternative directional implicit difference scheme and the Eulerian-Lagrangian method is used to solved the shallow water equations. The hydrodynamic equilibrium of the lagoon is determined by the tidal currents and by fresh water from the catchment. The tide waves which enter the lagoon are not dampened in amplitude, and there is only a small time lag in the effects of the tide in the whole lagoon. The friction coefficient and the turbulent kinetic viscosity have been evaluated by comparison with the collected field data. The spatial and temporal distribution of the salinity has been used to calibrate the diffusion model and validate the hydrodynamic model.