STANMOD for Windows, Version: 2.xx, December 2003
Concentration movement
STANMOD (STudio of ANalytical MODels) is a public domain Windowsbased computer software package for evaluating solute transport in porous media using analytical solutions of the convectiondispersion solute transport equation.
Authors:
J. Simunek, M.Th. van Genuchten, M. Sejna, N. Toride and F. J. Leij
References:
Šimůnek, J., M. Th. van Genuchten, M. Šejna, N. Toride, and F. J. Leij, The STANMOD computer software for evaluating solute transport in porous media using analytical solutions of convectiondispersion equation. Versions 1.0 and 2.0, IGWMC  TPS  71, International Ground Water Modeling Center, Colorado School of Mines, Golden, Colorado, 32pp., 1999.
van Genuchten, M. Th., J. Šimůnek, F. L. Leij, N. Toride, and M. Šejna, STANMOD: Model use, calibration and validation, special issue Standard/Engineering Procedures for Model Calibration and Validation, Transactions of the ASABE, 5(4), 13531366, 2012.
The Program

Support and Links

Models for 1Dtransport problems
 CXTFIT 2.0 [Toride et al., 1995]
 CFITM [van Genuchten,1980]
 CFITIM [van Genuchten, 1981]
 CHAIN [van Genuchten, 1985]
 SCREEN [Jury et al., 1983]

Models for 2D and 3Dtransport problems
 3DADE [Leij and Bradford, 1994]
 N3DADE [Leij and Toride, 1997]

CXTFIT
Main Window The software package includes a modified and updated version of the CXTFIT code of Toride et al.[1995] for estimating solute transport parameters using a nonlinear leastsquares parameter optimization method. This code may be used to solve the inverse problem by fitting a variety of analytical solutions of theoretical transport models, based upon the onedimensional advectiondispersion equation (ADE), to experimental results. The program may also be used to solve the direct or forward problem to determine concentrations as a function of time and/or position. Three different onedimensional transport models are considered: (i) the conventional equilibrium ADE; (ii) the chemical and physical nonequilibrium ADEs; and (iii) a stochastic stream tube model based upon the localscale equilibrium or nonequilibrium ADE.
CFITM
Project Manager STANMOD also comes with an updated version of the CFITM code of van Genuchten [1980] for analyzing observed column effluent data using analytical solutions of the onedimensional equilibrium advectivedispersive transport equation. The code considers analytical solutions for both semifinite and finite columns.
CFITIM
Results  Concentration Profiles STANMOD also contains an updated version of the CFITIM code of van Genuchten [1981] for analyzing observed column effluent data using analytical solutions of the onedimensional equilibrium and nonequilibrium advectivedispersive transport equations. The code involves analytical solutions for semifinite columns. The nonequilibrium solutions consider the tworegion dualporosity (bicontinuum) flow model for physical nonequilibrium and the onesite or twosite sorption models for chemical nonequilibrium. The model provides an easy to use, efficient and accurate means of determining various transport parameters by optimizing column effluent data. CFITIM represents a simple alternative to the much more comprehensive, but also more complex, CXTFIT model.
CHAIN
In addition, STANMOD 1.xx includes the modified and updated CHAIN code of van Genuchten [1985] for analyzing the advectivedispersive transport of solutes involved in sequential firstorder decay reactions. Examples are the migration of radionuclides in which the chain members form firstorder decay reactions, and the simultaneous movement of various interacting nitrogen or organic species.
SCREEN
This behavior assessment model of Jury et al. (1983) describes the fate and transport of soilapplied organic chemicals. The model assumes linear, equilibrium partitioning between vapor, liquid, and adsorbed chemical phases, net first order degradation, and chemical losses to the atmosphere by volatilization through a stagnant air boundary layer above the soil surface. The model is intended to classify and screen organic chemicals for their relative susceptibility to different loss pathways (volatilization, leaching, degradation) in soil and air. SCREEN requires knowledge of the organic carbon partition coefficient (K_oc), Henry's constant (K_h), and a net firstorder degradation rate coefficient or the chemical halflife. These parameters for selected chemicals provided in the STANMOD software are taken from Jury et al. (1984).
3DADE
Model Selection Dialog STANMOD 2.xx includes the 3DADE code of Leij and Bradford [1994] for evaluating analytical solutions for two and threedimensional equilibrium solute transport in the subsurface. The analytical solutions assume steady unidirectional water flow in porous media having uniform flow and transport properties. The transport equation contains terms accounting for solute movement by advection and dispersion, as well as for solute retardation, firstorder decay, and zeroorder production. The 3DADE code can be used to solve the direct problem, i.e., the concentration is calculated as a function of time and space for specified model parameters, and the indirect (inverse) problem in which the program estimates selected transport parameters by fitting one of the analytical solutions to specified experimental data.
N3DADE
Graphical display of results Finally, STANMOD 2.xx also incorporates the N3DADE code of Leij and Toride [1997] for evaluating analytical solutions two and threedimensional nonequilibrium solute transport in porous media. The analytical solutions pertain to multidimensional solute transport during steady unidirectional water flow in subsurface systems of semiinfinite length in the longitudinal direction, and of infinite length in the transverse direction. The solutions can be applied also to one and twodimensional problems. The flow and transport properties of the medium are again assumed to be macroscopically uniform. Nonequilibrium solute transfer can occur between two domains in either the liquid phase (physical nonequilibrium) or the absorbed phase (chemical nonequilibrium). The transport equation contains terms accounting for solute movement by advection and dispersion, as well as for solute retardation, firstorder decay, and zeroorder production.
User Interface
A Microsoft Windowsbased graphical user interface (GUI) is largely based on libraries developed for the Hydrus1D and Hydrus2D software packages [Simunek et al., 1998, 1999]. It manages the input data required to run STANMOD, as well as for editing, parameter allocation, problem execution, and visualization of results. All computational programs were written in FORTRAN, and the graphic interface in MS Visual C++. The preprocessing unit includes specification of all necessary parameters to successfully run the FORTRAN codes.
Both input and output can be examined using graphical tools.
File management is handled by means of a sophisticated project manager.
PostProcessing
Postprocessing is also carried out in the shell.
The postprocessing unit consists of simple xy plots for graphical presentation of the results (and data) and a dialog window that displays an ASCII output file.
Two and threedimensional solutions (3DADE and N3DADE) are supported with output graphics that include 2D contours (isolines or color spectra) in areal or crosssectional view for equilibrium, nonequilibrium, and total concentrations. Output also includes animation of graphic displays for sequential timesteps, and linegraphs for selected boundary or internal sections, and for variableversustime plots. Areas of interest can be zoomed into, and vertical scale can be enlarged for crosssectional views. Viewing of grid and/or spatially distributed results (concentrations) is facilitated using high resolution color or gray scales.
Peripheral devices supported include most popular types of printers and plotters.
Extensive contextsensitive, online Help is part of the interface.
Examples distributed with the model
Direct  CXTFIT: Direct Problems
 Fig1010  Tworegion model, effect of the retardation factor, Cf(T)
 Fig1010a  Tworegion model, effect of the retardation factor, Cf(Z)
 Fig1010b  Tworegion model, effect of the retardation factor, Cr(Z)
 Fig1011  Tworegion model, effect of the mass transfer coefficient, Cf(T)
 Fig1011a  Tworegion model, effect of the mass transfer coefficient, Cf(Z)
 Fig1011b  Tworegion model, effect of the mass transfer coefficient, Cr(Z)
 Fig1012  Tworegion model, effect of the Peclet number, Cf(T)
 Fig1012a  Tworegion model, effect of the Peclet number, Cf(T)
 Fig1012b  Tworegion model, effect of the Peclet number, Cr(T)
 Fig105  Equilibrium model, Effect of firstorder decay, Step Input
 Fig105a  Equilibrium model, Effect of firstorder decay, Pulse Input
 Fig108  OneSite Model, Effect of masstransfer coefficient
 Fig109  Tworegion model, effect of mobile/immobile water ratio, Cf(T)
 Fig109a  Tworegion model, effect of mobile/immobile water ratio, Cf(Z)
 Fig109b  Tworegion model, effect of mobile/immobile water ratio, Cr(Z)
 Fig51  Firstorder nonequilibrium model, effect of beta and alpha
 Fig52  Firstorder nonequilibrium model, effect of beta and f
 Fig71  Fig.71: The deterministic CDE (BVP+PVP)
 Fig72a  Fig.72: Flux vs. (resident) conc. for the IVP, Cf(Z), (a) P=2 (b)P=10
 Fig72b  Fig.72: (Flux) vs. resident conc. for the IVP, Cr(Z), (a) P=2 (b)P=10
 Fig75  Fig.75: Nonequilibrium onesite CDE (Beta=1/R, Alpha=0.08,0.2,1.0,10)
 Fig76a  Fig76a. Twosite CDE (Alpha=0.08, f=0, 0.3, 0.7, 0.99875)
 Fig76b  Fig76b: Twosite CDE (Alpha=0.2, f=0, 0.3, 0.7, 0.99875)
 Fig77a  Fig.77a: Twosite CDE for Beta.R=0.22  Dirac input
 Fig77b  Fig.77b: Twosite CDE for Beta.R=0.22  pulse input
 Fig78  Fig.78: IVP for the nonequilibrium CDE
Inverse  CXTFIT: Inverse Problems
 Fig712  Fig.712: Fieldscale bromide movement (after Jury at al., 1982)
 Fig715  Fig.715: Hypothetical fieldscale reactive solute transport
 Fig73a  Fig.73a: Steady saturated flow in a sand column
 Fig73b  Fig.73b: Steady saturated flow in a sand column
 Fig74  Fig.74: Estimation of duration time (MASS = 1 in Block B)
 Fig79a  Fig.79a: Tritium effluent curve from Glendale clay loam
 Fig79b  Fig.79b: Boron effluent curve (exp.31, van Genuchten, 1974)
Stochast  CXTFIT: Stochastic Problems
 Fig45a  Fig4.5: Stream tube model (STM) with a random v, BVP vs (IVP)
 Fig45b  Fig4.5: Stream tube model (STM) with a random v, (BVP) vs IVP
 Fig47a  Fig4.7: STM with a random v, Constant and (variable) duration
 Fig47b  Fig4.7: STM with a random v, (Constant) and variable duration
 Fig710  Fig.710: STM with a random v, Effect of sigma v
 Fig711a  Fig.711: STM with a random v, ensembleaveraged flux conc.,
 Fig711b  Fig.711: STM with a random v, fieldscale flux conc., cf
 Fig711c  Fig.711: STM with a random v, fieldscale resident conc., cr
 Fig713  Fig.713: STM with a random v and Kd, effect of correlation vKd
 Fig714a  Fig.714: Nonequilibrium fieldscale transport (Mode=4), fieldscale cr
 Fig714b  Fig.714: Nonequilibrium fieldscale transport (Mode=4), fieldscale ct
Chain  FirstOrder Decay Chains
 Nitrogen  Example 1: Nitrogen chain (Cho, 1972)
 Radionuc  Example 2: Radionuclide Transport
CFitM  Equilibrium Examples
 Direct1  Effect of Peclet Number
 Direct2  Effect of Retardation Factor
 Example1  Example 2A: Chromium (Column Number 4)  SemiFinite Sytem
 Example2  Example 2B: Chromium (Column Number 4)  Finite Sytem
CFitIm  Nonequilibrium Examples
 Direct1  Effect of Peclet Number
 Direct2  Effect of Retardation Factor
 Direct3  Effect of MobileImmobile Fraction
 Direct4  Effect of Mass Transfer Coefficient
 Direct5  Effect of Pulse Time
 Example1  Nonequilibrium model, generated data
 Example2  Example 2D: Tritiated water (EXP. 52); Nonequilibrium Model
 Example3  Example 2H: Tritiated water (EXP. 52); Linear Adsorption
 Fig79a  Tritium effluent from Glendale clay loam; Nonequilibrium model
 Fig79b  Boron effluent (exp.31, van Genuchten, 1974); Nonequilibrium model
3DADE  Threedimensioal equilibrium transport
 Example1  Diffuse source in semiinfinite region of surface, SteadyS.
 Example2  Rectangular source at surface, Firsttype BC
 Example3  Rectangular source at surface, Thirdtype BC
 Example4  Parallelepipedal initial distribution, Thirdtype BC
 Example5  Circular source at surface, Thirdtype BC
 Example6  Diffuse source in semiinfinite region of surface, Firsttype BC
 Example7  Parallelepipedal initial distribution, Thirdtype BC
 Example8  Parallelepipedal initial distribution, Thirdtype BC
 Example9  Circular source at surface, Firsttype BC
N3DADE  Threedimensional nonequilibrium
 Exampl1a  BVP: Fig. 6: Instantaneous application from disc (cm,d)
 Exampl1b  BVP: Fig. 7: Instantaneous application from disc (cm,d)
 Exampl1c  BVP: Fig. 7: Instantaneous application from disc (cm,d), new output
 Exampl2a  BVP: Fig. 8: Heaviside application, Finite rectangle
 Exampl2b  BVP: Fig. 9: Heaviside application, Finite rectangle
 Example3  IVP: Fig. 10: Heaviside initial, Finite rectangle
 Example4  IVP: Fig. 11: Exponential distribution about (5,0,0), Spherical coordinate
 Example5  PVP: Fig. 12: Heaviside production, Circular coordinate
Screen  Screening Model
 Test1  Toluene: multiple fluxes
 Test2  Benzene: Multiple times
 Test3  Multiple solutes
System Requirements
Intel Pentium or higher processor, 16 Mb RAM, hard disk with at least 20 Mb free disk space, VGA graphics (High Color recommended), MS Windows 95, 98, NT, 2000, XP, Vistas
STANMOD References
 Jury, W. A., W. F. Spencer, and W. J. Farmer, Behavior assessment model for trace organics in soil: I. Description of model. J. Environ. Qual., 12(4), 558564, 1983.
 Jury, W. A., W. F. Spencer, and W. J. Farmer, Behavior assessment model for trace organics in soil: III. Application of screening model, J. Environ. Qual., 13(4), 573579, 1984.
 Leij, F. J., and S. A. Bradford, 3DADE: A computer program for evaluating threedimensional equilibrium solute transport in porous media, Research Report No. 134, U. S. Salinity Laboratory, USDA, ARS, Riverside, CA, 1994. ( Download PDF, 7Mb)
 Leij, F. J., and N. Toride, N3DADE: A computer program for evaluating nonequilibrium threedimensional equilibrium solute transport in porous media, Research Report No. 143, U. S. Salinity Laboratory, USDA, ARS, Riverside, CA, 1997. ( Download PDF, 10Mb)
 Leij, F. J., and N. Toride, Analytical solutions for nonequilibrium transport models, in Selim, H. M., and L. Ma (eds.) Physical Nonequilibrium in Soils, Modeling and Application, Ann Arbor Press, Chelsea, Michigan, 1998.
 Marquardt, D. W., An algorithm for leastsquares estimation of nonlinear parameters, SIAM J. Appl. Math. 11, 431441, 1963.
 Parker, J. C., and M. Th. van Genuchten, Determining transport parameters from laboratory and field tracer experiments, Bull. 843, Va Agric. Exp. St., Blaacksburg, Va, 1984.
 Šimůnek, J., M. Th. van Genuchten, M. Šejna, N. Toride, and F. J. Leij, The STANMOD computer software for evaluating solute transport in porous media using analytical solutions of convectiondispersion equation. Versions 1.0 and 2.0, IGWMC  TPS  71, International Ground Water Modeling Center, Colorado School of Mines, Golden, Colorado, 32 pp., 1999.
 Toride, N., F. J. Leij, and M. Th. van Genuchten, The CXTFIT code for estimating transport parameters from laboratory or field tracer experiments. Version 2.0, Research Report No. 137, U. S. Salinity Laboratory, USDA, ARS, Riverside, CA, 1995.
 van Genuchten, M. Th., Determining transport parameters from solute displacement experiments, Research Report No. 118, U. S. Salinity Laboratory, USDA, ARS, Riverside, CA, 1980. ( Download PDF, 2.7Mb)
 van Genuchten, M. Th., J. Šimůnek, F. L. Leij, N. Toride, and M. Šejna, STANMOD: Model use, calibration and validation, special issue Standard/Engineering Procedures for Model Calibration and Validation, Transactions of the ASABE, 5(4), 13531366, 2012.