Numerical Simulation of Hydrodynamics and Residence Time in Alpine Lake with Three-Dimensional Model

Abstract

Flows in the lakes are driven in most cases by shear stresses resulted from wind and freshwater inflow. The effect of wind-induced current has been studied through field observations, laboratory small-scale physical models, and numerical models to evaluate the impacts on hydraulic structures, mixing, and stratification. Typhoon-induced inflow, especially in Taiwan, is an important factor to affect the mixing in the water column. In the present study, a three-dimensional, time-dependent hydrodynamic model was performed and applied to the alpine Yuan-Yang Lake in northeastern region of Taiwan. The model was driven with discharge inflow, heat, and wind stress to simulate the hydrodynamics of lake. The model was validated with measured water surface elevation, current, and temperature in 2008. The overall model simulation results are in quantitative agreement with the observed data. The validated model was then used to investigate mean circulation and residence time in the YYL. The simulated mean current reveals that the surface currents flow toward the southwest direction and form a clockwise rotation. The calculated residence time is strongly dependent on the inflows and wind effects. The calculated residence time is approximately 2~2.5 days under low inflow with wind effect.