A Two-Dimensional Model for Water Quality Simulation in lakes and its Aplication to Tabiishidani Lake in Sasaguri : Fukuoka Prefecture,Japan

Abstract

The objective of this research is tQ build a two-dimensional, unsteady, Iaterally averaged model for simulating water quality in lakes. The model consists of calculation of flow field and water quality simulation in lakes. The main foundation of the model is twoHiimentional equations of the incompressible Navier-Stokes equations for circulation simulation and diffusion equations for water quality simulation. These equations were discret,ized by the finite volume method (FVM) and were solved for flow field velocities and water quality variables respectively by the SIMPLE (Semi-Implicit Method for Pressure-Linked Equations) algorithm (Patankar, 1980) wlth variables defined on a space-staggered rectangular grid. To solve these discretized equations effectively, a numerical method has been developed and coded in Fortran 90 (Nyhoff and Leestma, 1997; 1999) with using the Tri-Diagonal Matrix Algorithm (TDMA). To verify the model, Tabiishidani lake, which is located in Sasaguri-Fukuoka prefecture, Japan, was chosen as a case study. The Tabiishidani lake's water temperature, the size of cross-sections of the lake and meteorological data have been collected and used as the initial and boundary conditions for the model. After calibration, the model was applied to simulate water temperature in the Tabiishidani lake under different patterns of meteorology. Within this study, only water temperature was chosen to illustrate the methodology. However, this model can be extended to simulate any variable of water quality in lakes. The results of this research indicate that this model can be a useful tool for simulating water quality in lakes.