Numerical Simulation Of Flow Sediment And Contaminant Transport In Integrated Surface Subsurface Systems

Download or read book Numerical Simulation of Flow, Sediment, and Contaminant Transport in Integrated Surface-subsurface Systems written by Zhiguo He and published by . This book was released on 2007 with total page 392 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hydro-system within a watershed includes many environmental processes, such as rainfall, runoff, groundwater flow, infiltration, evapotranspiration, recharge, upland erosion, sediment transport, and contaminant transport. In order to investigate these processes and evaluate their effects on water environments, numerical models have been recognized as an increasingly efficient and effective tool. Due to the natural intrinsic connections between surface and subsurface waters, modeling of flow, upland soil erosion, and contaminant transport should be considered as an integrated system. This dissertation has developed a physically-based integrated numerical model for flow, sediment, and contaminant transport in the surface-subsurface system. In this model, the surface flow is calculated using a depth-averaged 2-D diffusion wave model, and the variably saturated subsurface flow is computed using the 3-D mixed-form Richards equation. Interactions between surface and subsurface flows are considered using the continuity conditions of the pressure head and exchange flux at the ground surface. A general form of the surface flow equation based on the diffusion wave approximation is developed, which is intrinsically coupled with the variably saturated subsurface flow equation. The upland soil erosion and transport model employs the concept of nonequilibrium that considers both erosion and deposition. The model simulates nonuniform total-load sediment transport, with detachments from rainsplash and/or hydraulic erosion driven by overland flow. Contaminant transports in both surface and subsurface domains are described using advection-diffusion equations. The model considers the sediment sorption and desorption of the contaminant, as well as contaminant exchanges between surface and subsurface due to infiltration, diffusion, and bed change. The integrated numerical model is evaluated by simulating several published laboratory- and field-scale experiments. It is further applied to compute flow discharge, sediment and pesticide concentration during storm events in the Deep Hollow Lake watershed, Mississippi. The sensitivity analysis of the model is also performed using different values for several model parameters. The results have shown that the integrated model framework is capable of simulating the rainfall-runoff related hydrological processes in natural surface-subsurface systems.