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    What's New Version 2.0 (Compared to Version 1.x)

    What's New with HYDRUS 2D/3D Version 1.02?

    The HYDRUS 2D/3D Model

    HYDRUS 2D/3D Levels

    HYDRUS 2D/3D User Interface

    Automatic FE-Mesh Generation in HYDRUS 2D/3D

    HYDRUS 2D/3D Post-Processing

    Two-Dimensional HYDRUS 2D/3D Examples Distributed With the Model

    Three-Dimensional HYDRUS 2D/3D Examples Distributed with the Model

    Other Existing HYDRUS 2D/3D Applications

    HYDRUS 2D/3D System Requirements

What's New with HYDRUS 2D/3D Version 2.0?

New Features and Changes (related to GUI):

1. Support for complex General three-dimensional geometries (3D-Professional Level).
2. Domain Properties, Initial Conditions, and Boundary Conditions can be specified on Geometric Objects (defining the transport domain) rather than on the finite element mesh.
3. New FE-mesh generator for unstructured 3D meshes. Supports mesh refinements and stretching.
4. Background layers facilitating graphical input of data.
5. Import of geometry and background layers from a number of formats (DXF, STL, TIN, BMP, ...)
6. Import of various quantities (e.g., domain properties, initial and boundary conditions) from another HYDRUS projects even with (slightly) different geometry or FE mesh.
7. Support of ParSWMS (a parallelized version of SWMS_3D).
8. Support of UNSATCHEM (a module simulating transport of and reactions between major ions).
9. Support of a new CWM1 constructed wetland module.
10. The Mass Balance (Inverse) Information dialog window enables to display texts larger than the capacity of the Edit window.
11. Constructed Wetland Parameters commands added to the main menu and navigation tree.
12. Root distribution can be specified using GUI parallel with the slope of hillslopes.
13. Display of results using Isosurfaces.
14. On-line activation and deactivation. HYDRUS 2.x can be activated and/or deactivated via internet without asking for activation codes.

New Features and Changes (related to computational modules):

1. New, more efficient algorithm for particle tracking. Time-step control to guarantee smooth particle paths.
2. Initial conditions can be specified in the total solute mass (previously only liquid phase concentrations were allowed).
3. Initial equilibration of nonequilibrium solute phases with equilibrium solute phase (given in initial conditions).
4. Gradient Boundary Conditions (users can specify other than unit (free drainage) gradient boundary conditions).
5. A subsurface drip boundary condition (with a drip characteristic function reducing irrigation flux based on the back pressure).
6. A surface drip boundary condition with dynamic wetting radius.
7. A seepage face boundary condition with a specified pressure head.
8. Triggered Irrigation - irrigation is triggered by HYDRUS when the pressure head at a particular observation node drops below a specified value.
9. Time-variable internal pressure head or flux nodal sinks/sources (previously only constant internal sinks/sources).
10. Fluxes across meshlines in the computational module for multiple solutes (previously only for one solute).
11. HYDRUS calculates and reports surface runoff, evaporation, and infiltration fluxes for the atmospheric boundary.
12. Water content dependence of solute reactions parameters using the Walker’s [1974] formula was implemented. (Walker, A., A simulation model for prediction of herbicide persistence, J. Environ. Quality, 3(4), 396-401, 1974.)
13. An option to consider root solute uptake, including both passive and active uptake [Šimunek and Hopmans, 2009].
14. The Per Moldrup’s tortuosity models [Moldrup et al., 1997, 2000] were implemented as an alternative to the Millington and Quirk [1960] model.
15. An option to use a set of Boundary Condition records multiple times.
16. Executable programs are about 1.5 - 3 times faster than in the standard version due to the loop vectorization.
17. A new CWM1 constructed wetland module (in addition to the CW2D module).
18. New options related to the fumigant transport (e.g., removal of tarp, temperature dependent tarp properties, additional injection of fumigant).

Fixed Errors:

1. Fixed error: The Wetland module had a wrong format statement when writing the CumQ.out file.
2. Fixed error: FE-mesh generation could fail if stretching factors were >1 and the domain boundary contained polylines and (at the same time) splines or arcs.
3. Fixed error: Activation energy coefficients in the temperature dependence functions were incorrectly converted when time units changed.
4. Fixed error: Unit conversion of the area associated with transpiration was incorrect when length units changed.
5. Fixed error: Conversion of some first- and zero-order rate constants with respect to length units.

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What's New with HYDRUS 2D/3D Version 1.02?

• HYDRUS 2D/3D installation program has been optimized for Windows Vista
• Colors for graphical display of Materials, Sub-regions and Anisotropy can now be customized within the groundwater model HYDRUS 2D/3D
• New option for importing domain geometry from a text file in HYDRUS 2D/3D; there is a new key word that allows for the import of thickness variables with multiple sub-layers with variable thickness into the groundwater model

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The HYDRUS 2D/3D Model

HYDRUS 2D/3D is a Windows based modeling environment for analysis of groundwater flow and solute transport in variably saturated porous media. Computational finite element models are included in HYDRUS 2D/3D for simulating both 2D and 3D transport of water, heat and solutes in variably saturated media. A parameter optimization algorithm is also available in HYDRUS 2D/3D for inverse modeling of soil hydraulic and/or solute transport parameters. HYDRUS 2D/3D is also supported by an interactive graphics-based interface for data pre-processing, generation of structured and unstructured finite element mesh, and graphic presentation of the result

The HYDRUS 2D/3D program is a finite element model for simulating the two- and three-dimensional movement of water, heat, and multiple solutes in variably saturated media. The HYDRUS 2D/3D program numerically solves the Richards equation for saturated-unsaturated water flow and convection-dispersion type equations for heat and solute transport. The flow equation in HYDRUS 2D/3D incorporates a sink term to account for water uptake by plant roots. The heat transport equation in HYDRUS 2D/3D considers movement by conduction as well as convection with flowing water. The governing convection-dispersion solute transport equations in HYDRUS 2D/3D are written in a very general form by including provisions for nonlinear nonequilibrium reactions between the solid and liquid phases, and linear equilibrium reaction between the liquid and gaseous phases. Hence, both adsorbed and volatile solutes such as pesticides can be considered. The solute transport equations in HYDRUS 2D/3D also incorporate the effects of zero-order production, first-order degradation independent of other solutes, and first-order decay/production reactions that provides the required coupling between the solutes involved in the sequential first-order chain. The HYDRUS 2D/3D transport model also accounts for convection and dispersion in the liquid phase, as well as for diffusion in the gas phase, thus permitting one to simulate solute transport simultaneously in both the liquid and gaseous phases. HYDRUS 2D/3D at present considers up to fifteen solutes which can be either coupled in a unidirectional chain or may move independently of each other. Physical nonequilibrium solute transport within HYDRUS 2D/3D can be accounted for by assuming a two-region, dual porosity type formulation which partition the liquid phase into mobile and immobile regions. HYDRUS 2D/3D also includes attachment/detachment theory, including the filtration theory, to simulate transport of viruses, colloids, and/or bacteria.

HYDRUS 2D/3D may be used to analyze water and solute movement in unsaturated, partially saturated, or fully saturated porous media. HYDRUS 2D/3D can handle flow domains delineated by irregular boundaries. The flow region itself in HYDRUS 2D/3D may be composed of nonuniform soils having an arbitrary degree of local anisotropy. Flow and transport can occur in the vertical plane, the horizontal plane, a three-dimensional region exhibiting radial symmetry about a vertical axis, or in a three-dimensional region in HYDRUS 2D/3D.

The water flow part of HYDRUS 2D/3D can deal with (constant or time-varying) prescribed head and flux boundaries, as well as boundaries controlled by atmospheric conditions. Soil surface boundary conditions in HYDRUS 2D/3D may change during the simulation from prescribed flux to prescribed head type conditions (and vice versa). HYDRUS 2D/3D can also handle a seepage face boundary through which water leaves the saturated part of the flow domain, and free drainage boundary conditions. Nodal drains are represented in HYDRUS 2D/3D by a simple relationship derived from analog experiments.

For solute transport HYDRUS 2D/3D supports both (constant and varying) prescribed concentration (Dirichlet or first-type) and concentration flux (Cauchy or third-type) boundaries. The dispersion tensor in HYDRUS 2D/3D includes a term reflecting the effects of molecular diffusion and tortuosity.

The unsaturated soil hydraulic properties of HYDRUS 2D/3D are described using van Genuchten [1980], Brooks and Corey [1964], Durner [1994], Kosugi [1995], and modified van Genuchten type analytical functions. Modifications for HYDRUS 2D/3D were made to improve the description of hydraulic properties near saturation. The HYDRUS 2D/3D code incorporates hysteresis by using the empirical model introduced by Scott et al. [1983] and Kool and Parker [1987]. HYDRUS 2D/3D assumes that drying scanning curves are scaled from the main drying curve, and wetting scanning curves from the main wetting curve. As an alternative, HYDRUS 2D/3D also incorporated the hysteresis model of Lenhard et al. [1991] and Lenhard and Parker [1992] that eliminates pumping by keeping track of historical reversal points. HYDRUS 2D/3D also implements a scaling procedure to approximate hydraulic variability in a given soil profile by means of a set of linear scaling transformations which relate the individual soil hydraulic characteristics to those of a reference soil.

The governing equations in HYDRUS 3D are solved numerically using a Galerkin type linear finite element method applied to a network of triangular elements. Integration in time in HYDRUS 3D is achieved using an implicit (backwards) finite difference scheme for both saturated and unsaturated conditions. HYDRUS 2D/3D' resulting equations are solved in an iterative fashion, by linearization and subsequent Gaussian elimination for banded matrices, a conjugate gradient method for symmetric matrices, or the ORTHOMIN method for asymmetric matrices. Additional measures are taken to improve HYDRUS 2D/3D' solution efficiency in transient problems, including automatic time step adjustment and checking if the Courant and Peclet numbers do not exceed preset levels. The water content term in HYDRUS is evaluated using the mass-conservative method proposed by Celia et al. (1990). To minimize numerical oscillations upstream weighing is included in HYDRUS 2D/3D as an option for solving the transport equation. In addition, HYDRUS 2D/3D implements a Marquardt-Levenberg type parameter estimation technique for inverse estimation of selected soil hydraulic and/or solute transport and reaction parameters from measured transient or steady-state flow and/or transport data (only in 2D). The procedure permits several unknown parameters to be estimated from observed water contents, pressure heads, concentrations, and/or instantaneous or cumulative boundary fluxes (e.g., infiltration or outflow data) within HYDRUS 2D/3D. Additional retention or hydraulic conductivity data, as well as a penalty function for constraining the optimized parameters to remain in some feasible region (Bayesian estimation), can be optionally included in HYDRUS 2D/3D in the parameter estimation procedure. A new module simulating the biochemical transformation and degradation processes in subsurface-flow constructed wetlands was developed for two-dimensional applications of HYDRUS 2D/3D (Langergraber and Simunek, 2005). This module considers the biochemical degradation and transformation processes for three fractions of organic matter (readily- and slowly-biodegradable, and inert), four nitrogen compounds (ammonium, nitrite, nitrate, and dinitrogen), inorganic phosphorus, and heterotrophic and autotrophic micro-organisms, and dissolved oxygen.

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HYDRUS 2D/3D Levels

HYDRUS 2D/3D is distributed in five different versions (Levels) so that users are provided with the flexibility of acquiring only that segment of the software that is most appropriate for their application. Users can select software limited to general two-dimensional applications (the 2D-Standard Level, which corresponds with former HYDRUS 2D/3D with MeshGen-2D) or for both two- and three-dimensional applications (i.e., the general two-dimensional base and layered third dimension, 3D-Standard). Users can also opt for relatively simple and more complex geometries in HYDRUS 2D/3D (two-dimensional rectangular geometries – 2D-Lite (which corresponds with former HYDRUS-2D without MeshGen-2D) or three-dimensional hexahedral geometries – 3D-Standard). We expect to release a version of HYDRUS 2D/3D in summer of 2010 that will accommodate general three-dimensional geometries (3D-Professional). Users are able to upgrade to higher HYDRUS 2D/3D Levels, as well as from older software (HYDRUS-2D or HYDRUS-2D/MESHGEN-2D) to any new HYDRUS Level.

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HYDRUS 2D/3D User Interface

A Microsoft Windows based Graphical User Interface (GUI) manages inputs required to run HYDRUS 2D/3D, as well as grid design and editing, parameter allocation, problem execution, and visualization of results. HYDRUS 2D/3D includes a set of controls that allows the user to build a flow and transport model, and to perform graphical analyses on the fly. Both input and output in HYDRUS 2D/3D can be examined using areal or cross-sectional views, and line graphs. The main program unit of the HYDRUS 2D/3D Graphical User Interface (GUI) defines the overall computational environment of the system. This main module controls execution of HYDRUS 2D/3D and determines which other optional tools are necessary for a particular application. The module contains a project manager and both the pre-processing and post-processing units. The pre-processing unit includes specification of all necessary parameters to successfully run the HYDRUS 2D/3D FORTRAN codes, grid generators for relatively simple rectangular and hexahedral transport domains, a grid generator for unstructured finite element meshes for complex two-dimensional domains, a small catalog of soil hydraulic properties, and a Rosetta Lite program for generating soil hydraulic properties from soil textural data.

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Automatic FE-Mesh Generation in HYDRUS 2D/3D

Data preprocessing in HYDRUS 2D/3D involves specification of the two-dimensional flow region having an arbitrary continuous shape bounded by polylines, arcs and splines, discretization of domain boundaries, and subsequent generation of an unstructured finite element mesh. HYDRUS 2D/3D (Standard Levels) comes with an optional mesh generation program Meshgen that generates unstructured finite element mesh for two-dimensional domains. This program, based on Delaunay triangulation, is seamlessly integrated in the HYDRUS 2D/3D environment. In the absence of the Meshgen program, the HYDRUS 2D/3D GUI provides an option for automatic construction of simple, structured grids (Lite Levels). The third dimension is in both HYDRUS 2D/3D Lite and HYDRUS 2D/3D Stadard levels developed by adding specified number of layers of equal or different thicknesses.

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HYDRUS 2D/3D Post-Processing

Output graphics in HYDRUS 2D/3D include 2D contours (isolines or color spectra) in areal or cross-sectional view for heads, water contents, velocities, concentrations, and temperatures. HYDRUS 2D/3D output also includes velocity vector plots, color edges, color points, animation of graphic displays for sequential time-steps, and line-graphs for selected boundary or internal sections. The post-processing unit of HYDRUS 2D/3D also includes simple x-y graphics for graphical presentation of soil hydraulic properties, as well as such output as distributions versus time of a particular variable at selected observation points, and actual or cumulative water and solute fluxes across boundaries of a particular type. Areas of interest can be zoomed into, and vertical scale can be enlarged for cross-sectional views. The HYDRUS 2D/3D mesh can be displayed with boundaries, and numbering of triangles, edges and points. Observation points can be added anywhere in the grid. Viewing of grid and/or spatially distributed results from HYDRUS 2D/3D (pressure head, water content, velocity, or concentration) is facilitated using high resolution color or gray scales. Extensive context-sensitive, online HYDRUS 2D/3D Help is part of the interface.

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Two-Dimensional HYDRUS 2D/3D Examples Distributed With the Model

• Column infiltration test
• Water flow and solute Transport in a field soil profile under grass - seasonal simulation
• Two-dimension unidirectional solute transport - comparison with analytical solution
• One-dimensional solute transport with nitrification chain - comparison with analytical solution
• One-dimensional solute transport with nonlinear cation adsorption - Data from Selim et al. (1987)
• One-dimensional solute transport with non-equilibrium cation adsorption
• Axisymetrical three-dimensional water and solute infiltration test
• One-dimensional water flow with multiple hysteretic loops, data from Lenhard et al. (1991)
• Water flow and solute transport from furrow to a drain
• Three wetland examples

• Parameter estimation from a cone penetrometer experiment (Gribb et al., 1987) Parameter estimation from a tension disc infiltrometer experiment (Simunek et al., 1998)

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Three-Dimensional HYDRUS 2D/3D Examples Distributed with the Model

• Column infiltration test
• Water flow and solute Transport in a field soil profile under grass - seasonal simulation
• Three-dimension unidirectional solute transport - comparison with analytical solution
• One-dimensional solute transport with nitrification chain - comparison with analytical solution
• One-dimensional solute transport with nonlinear cation adsorption - Data from Selim et al. (1987)
• One-dimensional solute transport with non-equilibrium cation adsorption
• One-dimensional solute transport with first-order attachment
• One-dimensional water flow with multiple hysteretic loops, data from Lenhard et al. (1991)
• Three-dimensional contaminant transport from a waste disposal site
• Three-dimensional flow and transport through a dike with a seepage face and root water uptake

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Other Existing HYDRUS 2D/3D Applications

• Irrigation management
• Drip irrigation design
• Sprinkler irrigation design
• Tile drainage design - flow to a drainage system
• Crop grow models, i.e., cotton model
• Salinization and reclamation processes, salt leaching
• Movement of pesticides; nonpoint source pollution
• Seasonal simulation of water flow and plant response

• Deep percolation beneath final closure cap designs for radioactive waste management sites at the Nevada test site
• Flow around nuclear subsidence craters at the Nevada test site
• Capillary barrier at the Texas low-level radioactive waste disposal site
• Evaluation of approximate analytical analysis of capillary barriers
• Landfill covers with and without vegetation
• Risk analysis of contaminant plume from landfills
• Seepage of wastewater from land treatment systems
• Tunnel design - flow around buried objects
• Highway design - road construction - seepage
• Stochastic theory - solute transport in heterogeneous media
• Lake basin recharge analysis
• Interaction between groundwater aquifers and streams
• Environmental impact of the drawdown of shallow water tables
• Analysis of cone permeameter and tension infiltrometer experiments

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HYDRUS 2D/3D System Requirements

• Operating System Windows NT 4.0 (SP3 or higher) / 2000 / XP
• X86 CPU with 1 GHz
• 512 MB RAM
• 10 GB total hard disk capacity with about 500 MB reserved for installation
• Graphic card with a resolution of 1024 x 768 pixels

To use HYDRUS 2D/3D comfortably for calculation of 3D models, we recommend the following system requirements:

• Operating System Windows 2000 / XP
• X86 CPU (Intel or AMD) with 3 GHz
• 1,024 MB memory
• 80 GB hard disk capacity
• Graphic card with OpenGL hardware acceleration

HYDRUS 2D/3D runs on these systems but we do not guarantee error-free functionality of the program on these OS.

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HYDRUS 2D/3D Summary

HYDRUS 2D/3D New Features