Development of a watershed numerical model

This paper presents a numerical model of watershed systems for coupled flow and transport modeling. The surface water components include both river/stream networks and overland flow regime. Since no single approach for solving the Saint-Vanent equations is numerically accurate and robust in terms of convergency and stability, three approaches, namely, the full dynamic wave, simplified kinematic wave and diffusion wave models, were included for different conditions of channel and overland bottom slopes. Internal river junctions and hydraulic structures such as weirs or gates were incorporated. Water flow in subsurface media is simulated by modified Richard's equation. Sediment and reactive chemical transport are both taken into account. With emphasis on one dimensional river/stream networks module, mathematical formulation and numerical approach of each module were described.