Hydrodynamics, transport time scales and water temperature dynamics in heavily anthropized eutrophic coastal lagoon

Coastal lagoons highly contribute to the recreational, ecological, and commercial value of their located areas and are often highly susceptible to natural and anthropogenic variables. An understanding of the dynamics of this system due to natural and anthropogenic drivers is essential for its proper management. Localised in-situ measurements are insufficient to characterize the complex dynamic processes spatially distributed in the lagoon, therefore a numerical model becomes an essential tool to capture these processes. In the present study, a numerical model validated with field monitoring is proposed to assess the impact of natural and anthropogenic drivers on indicators of hydrodynamic, water temperature, and residual currents to deepen the quantitative understanding of an anthropic lagoon. The Orbetello Lagoon, located on the southern coast of Tuscany (Italy), has served as a test case. It is a strong anthropized, semi-enclosed coastal system with a very eutrophic environment, that is heavily used for its aquaculture value. It is connected to the Mediterranean Sea through three narrow channels where fishing structures are located, obstructing the water inflow and outflow. To increase the water exchange between the lagoon and the sea, pumps are installed in each channel and are activated mainly during the spring and summer months. The numerical model proved to be a valuable system for lagoon management, as it is a tool to understand the role of different natural and anthropogenic drivers on the lagoon dynamics and to test the effectiveness of different strategies, e.g. the operational strategies of the pump system in synergy with the natural drivers to maximize its value of use while limiting the consumption of energy.