Numerical simulation of water exchange capacity in the Dingzi bay

In this paper, we established a three-dimensional high-resolution hydrodynamic numerical model of Dingzi bay using the Finite Volume Community Ocean Model (FVCOM). Utilizing the DYE-RELEASE module, we released dye tracers into the simulation domain to investigate the water exchange capacity, and the half-life time was used as the metric for this evaluation. The water volume entered the bay through its middle channel and subsequently diverged towards the shores. During ebb tide, the water volume within the bay converged towards the channel and flew out through the middle channel at the mouth. Consequently, the current velocity was larger in the channel and weaker on both shoresides. The inflow was northwest, and outflow was southeast. The vertically averaged current velocity during the flood slack tide exceeded 1.2 m/s, while during the ebb slack tide, it exceeded 1.0 m/s. Consequently, the maximum inflow was slightly greater than the maximum outflow. The average half-life time of Dingzi bay ranged from 9.6 days to 11.2 days. The water exchange capacity of the bay was stronger during spring tide than neap tide. Notably, the closer the location was to the bay mouth, the shorter the half-life time. The half-life time in the bay mouth area was less than 10 days, while in the middle area, it ranged from approximately 10 to 35 days, and at the end of the bay, it typically exceeded 35 days.