This study focuses on Fuxian Lake, the largest deep freshwater lake in China, and carries out numerical solution and quantitative analysis of hydrodynamics and thermal stratification phenomena. A three-dimensional hydrodynamic model was established using the high-fidelity Environmental Fluid Dynamics Code (EFDC), considering the variation of bottom elevation, and the model was preliminarily validated using measured data. The simulation results are as follows: First, the spatiotemporal characteristics of the thermocline are strongly influenced by meteorological conditions and hydrodynamic processes. Wind speed and temperature differences mainly affect the water flow, with the maximum values of water temperature and thermocline intensity typically occurring in September. Second, vertical circulation is caused by horizontal divergence and convergence of lake currents driven by wind, leading to upward and downward lake currents and resulting in thermocline inhomogeneity. The results show that the EFDC model can well reproduce the observed spatiotemporal variations, laying the foundation for the future coupling of the EFDC model with water quality models. Moreover, the significance of this study lies in providing an effective method for researching the hydrodynamics and thermal stratification processes of other deep lakes around the world, and offering assistance for lake management and ecological restoration projects for other deep lakes globally.

Fuxian Lake; Thermal behavior;Numerical study; EFDC