Numerical simulation on water exchange affected by tidal and runoff in Xiaohai Lagoon, Hainan province

¹ Sanya Oceanographic Institution, Ocean University of China, Sanya, China
² College of Environmental Science and Engineering, Ocean University of China, Qingdao, China
³ Key Laboratory of Marine Environment and Ecology, Ministry of Education of China, Ocean University of China, Qingdao, China

^* Corresponding author: zxq@ouc.edu.cn

Abstract

Xiaohai Lagoon is the largest lagoon in Hainan, connected to the open sea through a narrow channel. In this study, a hydrodynamic numerical model based on the FVCOM model is established to quantitatively investigate the water exchange characteristics between Xiaohai Lagoon and the open sea under tidal and runoff conditions, utilizing concepts such as residual flow, tidal prism, and half-life time. Under the influence of runoff effect, the water exchange capacity in the lagoon has significant spatial variations, and the closer the distance to the estuary and inlet compared to the tidal drive, the faster the water exchange. The strongest areas of water exchange capacity in the Xiaohai lagoon are located in the mouth, tidal channel and estuary areas, and the weakest area is the southeastern part of the lagoon. The simulation results showed that the runoff input has a certain promotion effect on the water exchange in the lagoon, especially in the scouring effect of freshwater in the estuary area, the easier the water exchange between the sea areas.