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United States Department of Agriculture

Agricultural Research Service

Title: Models to Simulate Preferential/nonequilibrium Flow and Transport

Authors
item Simunek, Jirka - UC RIVERSIDE, CA
item Van Genuchten, Martinus

Submitted to: Soil Science Society of America Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: July 1, 2003
Publication Date: October 20, 2003
Citation: Simunek, J., Van Genuchten, M.T. 2003. Models to simulate preferential/nonequilibrium flow and transport. (CD-ROM). Soil Science Society of America Annual Meeting. Abstract. Nov. 2-6, Denver, CO.

Technical Abstract: We present a new version of the HYDRUS code that includes various approaches for modeling preferential and nonequilibrium flow and transport in the vadose zone. Existing approaches differ in terms of their underlying assumptions and complexity. They range from relatively simplistic models to more complex physically based dual-porosity and dual-permeability type models. A relatively simple dual-porosity flow model results when the Richards equation is combined with composite equations for the hydraulic properties to account for both soil textural and soil structural effects on flow. The simplest nonequilibrium flow model, a single-porosity model, which distinguishes between actual and equilibrium water contents, is based on a formulation by Ross and Smettem (2000) that requires only one additional parameter to account for nonequilibrium. A more complex dual-porosity, mobile-immobile water flow model results when the Richards or kinematic wave equations are used for flow in the fractures, and immobile water is assumed to exist in the matrix. We also discuss various dual-permeability models, including the formulation of Gerke and van Genuchten (1993a) and the kinematic wave approach as used in the MACRO model of Jarvis (1994). These models differ mainly in the description of the flow in the macropores. Several examples and comparisons of equilibrium and various nonequilibrium flow and transport models are also provided.

Last Modified: 7/25/2014
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