A Numerical Model Simulating Flow Contaminant And Sediment Transport In Watershed Systems Wash12d

Download or read book A Numerical Model Simulating Flow, Contaminant, and Sediment Transport in Watershed Systems (WASH12D). written by and published by . This book was released on 1998 with total page 211 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report presents the development of a numerical model simulating water flow, contaminant transport, and sediment transport in watershed systems. The model is composed of two modules: flow and transport. Three options are provided in modeling the flow module in river/stream network and overland regime: the kinematic wave approach, diffusion wave approach, and dynamic wave approach. The kinematic and diffusion wave approaches are known to be numerically robust in terms of numerical convergency and stability, i.e., they can generate convergent and stable simulations over a wide range of ground surface slopes in the entire watershed. The question is the accuracy of these simulations. The kinematic wave approach usually produces accurate solutions only over the region of steep slopes. The diffusion wave approach normally gives accurate solutions over the region of mild to steep slopes. However, neither approach has the ability to yield accurate solutions over the region of small slopes, in which the inertial forces are no longer negligible compared with the gravitational forces. The kinematic wave approach cannot even address the problems of backwater effects. On the other hand, a dynamic wave approach, having included all forces, can theoretically have the potential to generate accurate simulations over all ranges of slopes in a watershed. A total of eight groups of example problems were given in this report to demonstrate the capability of this model. Continuing work is underway to incorporate a three-dimensional subsurface flow and chemical transport model into this watershed model. The Richards' equation and advection-dispersion reactive chemical transport equations will form the basis to simulate the subsurface flow and chemical transport module in saturated-unsaturated media.