Author(s): Zhi-Qiang Deng; Hoon-Shin Jung
Linked Author(s): Zhiqiang Deng
Keywords: Longitudinal dispersion; Scale-dependence; Rivers; Variable residence time
Abstract: Modeling the longitudinal dispersion and transport of solute is of great importance to evaluating risks from accidental releases of hazardous contaminants in waterways and to understanding of nutrient retention in streams and rivers. Based on the mechanism of scaling dispersion and the mass conservation principle this paper develops a new scale-dependent dispersion model for natural rivers. The model is unique in that (1) a variable and actual residence time is used to describe the scale-dependent dispersion process and (2) the model contains only two unknown parameters and thus has less uncertainty as compared with existing dispersion models. The two parameters, transient storage volume fraction and the longitudinal Fickian dispersion coefficient, are calculated using field data and an existing method for estimation of the longitudinal dispersion coefficient. Two sets of tracer dispersion data observed from the Monocacy River are used to test the new dispersion model. The numerically simulated concentration distributions are in good agreement with the observed ones, demonstrating the efficacy of the new scale-dependent dispersion model presented in this paper. The new scale-dependent dispersion model will improve understanding and predictions of solute dispersion and transport in natural rivers and thus provide an efficient and cost effective tool for policy and decision makers, stream managers, and researchers.
Year: 2007