Numerical Analysis of Dissolved Oxygen Behavior in Lake Togo using 3-dimensional Eco-hydrodynamic Model

Abstract

A 3-dimensional eco-hydrodynamic model was developed to analyze the behavior of dissolved oxygen (DO) in Lake Togo, located in Tottori prefecture in Japan. Based on the observed data, the model simulated the behavior of water qualities in the lake. The results show that the model approximately reproduced the temporal and spatial variations of the water qualities observed in the field. It was concluded that the model could be applied to analysis of the lake's water environment. To investigate the occurrence mechanism of anoxic water, numerical experiments were carried out using the model. As a result, DO consumption by the bottom sediment exceeded the physical and biological supply of DO to the bottom water at the deepest point of the lake under wind velocity conditions of 3 m/s. Therefore, anoxic water appeared at the bottom layer in the southern part of the lake. Under wind velocity conditions of 6 m/s, the bottom water maintained high DO concentration because the physical supply of DO increased due to vertical circulation caused by strong wind stress.