A Comparison Study of Six Mediterranean Lagoons with Numerical Modelling

A numerical model (SHYFEM) has been applied to 6 Mediterranean lagoons and a comparison study between the lagoons has been carried out. The lagoons are the Venice lagoon and the Marano-Grado lagoon in the Northern Adriatic Sea, the Taranto basin in the Ionian Sea, the Cabras lagoon in Sardinia, the Mar Menor in Spain and the Nador lagoon in Morocco. These environments range from a leaky type of lagoons to a choked type and give a representative picture of the lagoons situated around the Mediterranean basin. This study has been mainly focused on hydrodynamics, exchange rates and residence time description. Wind and tidal stirring, which are the main forcings, normally prevent the lagoons from developing stratification, which justifies the application of the 2D version of the model. The exchange rate depends mainly on the inlet configuration, but also on the wind regimes in the case of multi-inlet lagoons. Residence time, which is mostly determined by the exchange rate, is a powerful concept that allows lagoons to be characterized with a time scale. In the case of the studied lagoons the residence time ranged from some days in the Marano-Grado lagoon to up to one year in the case of the Mar Menor. The analysis of the residence time frequency distribution allows identifying sub-basin and seasonal variations in the renewal time. The numerical study proved to be a powerful tool for the inter-comparison of the lagoons.