Short-term simulations under winter conditions in the lagoon of Venice: a contribution to the environmental impact assessment of temporary closure of the inlets

A primitive equation finite element hydrodynamic model developed for the lagoon of Venice some years ago has been internally coupled with the Streeter-Phelps module of Water Quality Analysis Simulation Program (WASP). The coupled model (VELFEEM) has been applied for a first evaluation of the impact on water quality of the lagoon of Venice induced by a reduction in the exchange with the Adriatic Sea, which could be caused by the temporary closure of the inlets. Such closures have been proposed to prevent the flooding (acqua-alta) of the historical city occurring in winter time and would be obtained by specifically designed mobile gates (MOSE). Short-term simulations of biochemical oxygen-dissolved oxygen (BOD-DO) dynamics are performed under winter conditions, in both the presence and the absence of the mobile closure. Results suggest that the mobile closures do not significantly affect the water quality of the lagoon, even in the case of repeated closures, and that, in any case, the lagoon seems to be able to return rather easily to its unperturbed condition when the inlets are open again.