Author
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SIMUNEK, JIRKA - UC RIVERSIDE, CA |
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Van Genuchten, Martinus |
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Submitted to: University of California-Riverside Research Reports
Publication Type: Other Publication Acceptance Date: 2/15/2006 Publication Date: 3/21/2006 Citation: Simunek, J., Van Genuchten, M.T. 2006. The HYDRUS Software Package for Simulating the Two- and Three-Dimensional Movement of Water, Heat, and Multiple Solutes in Variably-Saturated Media; Technical Manual, Version 1.0. University of California-Riverside Research Reports. 241 pp. Interpretive Summary: There is growing concern about the fate and transport of agricultural chemicals (salts, pesticides, pathogenic micro-organisms, fertilizers, heavy metals) in the subsurface. Computer models are now increasingly used to predict the future behavior of these chemicals, and to study alternative soil and water management practices aimed at reducing groundwater pollution while optimizing crop yield. This report documents version 1.0 of HYDRUS, a general software package for simulating the two- or three-dimensional movement of water, heat, and solutes in soils and groundwater. The program may be applied to both saturated systems (groundwater), or to unsaturated systems involving the vadose zone between the soil surface and the groundwater table. The software considers a range of processes important to agricultural, environmental and ecological application, including water uptake by plant roots, transpiration by a crop, evaporation from the soil surface, solute adsorption by the soil’s solid phase, and solute degradation, among many other features. Alternatively, the transport equations can also include provisions for kinetic attachment/detachment of solutes to the solid phase, and as such can be used to simulate the transport of viruses, colloids, or bacteria. Many examples are given showing application of the software to such problems as water and solute movement in one- and multi-dimensional field soil profiles, contaminant transport subject to non-equilibrium sorption, and pollutant transport from a waste disposal site. Detailed instructions are given for data input preparation. This report serves as both a technical manual and reference document. The graphical user interface (GUI) of the HYDRUS software package is documented in a separate user manual. The model provides theoretical and applied scientists and engineers with a much-needed tool for predicting water and chemical transport in the soils and grundwater. Technical Abstract: This report documents version 1.0 of HYDRUS, a general software package for simulating water, heat, and solute movement in two- and three-dimensional variably saturated media. The software package consists of a computation computer program, and an interactive graphics-based user interface. The HYDRUS program numerically solves the Richards equation for saturated-unsaturated water flow and the convection-dispersion equation for heat and solute transport. The flow equation incorporates a sink term to account for water uptake by plant roots. The heat transport equation considers transport due to conduction and convection with flowing water. The solute transport equations consider convective-dispersive transport in the liquid phase, as well as diffusion in the gaseous phase. The transport equations also include provisions for nonlinear nonequilibrium reactions between the solid and liquid phases, linear equilibrium reactions between the liquid and gaseous phases, zero-order production, and two first-order degradation reactions: one which is independent of other solutes, and one which provides the coupling between solutes involved in sequential first-order decay reactions. In addition, physical nonequilibrium solute transport can be accounted for by assuming a two-region, dual-porosity type formulation which partitions the liquid phase into mobile and immobile regions. Attachment/detachment theory, including filtration theory, is included to simulate the transport of viruses, colloids, and/or bacteria. The program may be used to analyze water and solute movement in unsaturated, partially saturated, or fully saturated porous media. The two-dimensional part of this program also includes a Marquardt-Levenberg type parameter optimization algorithm for inverse estimation of soil hydraulic and/or solute transport and reaction parameters from measured transient or steady-state flow and/or transport data for two dimensional problems. The governing flow and transport equations are solved numerically using Galerkin-type linear finite element schemes. Depending upon the size of the problem, the matrix equations resulting from discretization of the governing equations are solved using either Gaussian elimination for banded matrices, or a conjugate gradient method for symmetric matrices and the ORTHOMIN method for asymmetric matrices. Detailed instructions are given for data input preparation. The graphical user interface (GUI) of the Hydrus software package is documented in a separate user manual |
