£EPA
United States
Environmental Protection
Agency
Office of Research and
Development
Washington, DC 20460
EPA/600/R-94/028
March 1994
Identification and
Compilation of
Unsaturated/Vadose
Zone Models
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EPA/ 600/R- 94/028
March 1994
o
IDENTIFICATION AND COMPILATION OF
UNSATURATED/VADOSE ZONE MODELS
by
Paul K.M. van der Heijde
Colorado School of Mines
International Ground Water Modeling Center
Golden, Colorado 80401
CR-818720
Project Officer
Joseph R. Williams
Extramural Activities and Assistance Division
Robert S. Kerr Environmental Research Laboratory
Ada, Oklahoma 74820
ROBERT S. KERR ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
ADA, OKLAHOMA 74820
U.S. Environ r-- '^on Agency ^ Printed on Recycled Paper
Region 5, Library ., •_-':.".:..•)
77 West Jackson Bojisvard, 12th Floor
Chicago, 11 60504-3590
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DISCLAIMER NOTICE
The information in this document has been funded in part by the U.S. Environmental Protection
Agency under cooperative agreement # CR-818720 with the Colorado School of Mines, Golden, Colorado.
It has been subjected to the Agency's peer and administrative review, and it has been approved for
publication as an EPA document. Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.
All research projects making conclusions or recommendations based on environmentally related
measurements and funded by the Environmental Protection Agency are required to participate in the
Agency Quality Assurance Program. This project did not involve environmentally related measurements
and did not involve a Quality Assurance Project Plan.
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FOREWORD
EPA is charged by Congress to protect the Nation's land, air, and water systems. Under a mandate
of national environmental laws focused on air and water quality, solid waste management and the control
of toxic substances, pesticides, noise and radiation, the Agency strives to formulate and implement actions
which lead to a compatible balance between human activities and the ability of natural systems to support
and nurture life.
The Robert S. Kerr Environmental Research Laboratory is the Agency's center of expertise for
investigation of the soil and subsurface environment. Personnel at the laboratory are responsible for
management of research programs to: (a) determine the fate, transport and transformation rates of
pollutants in the soil, unsaturated and the saturated zones of the subsurface environment; (b) define the
processes to be used in characterizing the soil and subsurface environment as a receptor of pollutants;
(c) develop techniques for predicting the effect of pollutants on ground water, soil and indigenous
organisms; and (d) define and demonstrate the applicability and limitations of using natural processes,
indigenous to the soil and subsurface environment, for the protection of this resource.
Many contamination problems find their cause at or near the soil surface. Consequently, the
physical and (bio-)chemical behavior of these contaminants in the shallow subsurface is of critical
importance to the development of protection and remediation strategies. Mathematical models, representing
our understanding of such behavior, provide tools useful in assessing the extent of pollution problems and
evaluating means to prevent and remediate them. Increasingly, detailed understanding and subsequent
modeling of the near-surface zone is crucial in designing effective remediation approaches. At many sites,
this near-surface zone is only partially saturated with water, requiring specially designed mathematical
models. This report focuses on models that might prove useful in simulating contaminant levels in such
partially saturated systems.
The report is comprised of sections which overview considerations for modeling contaminant
transport in the unsaturated system, procedures for identifying existing models, and criteria for the selection
of models for application. The report includes appendixes which provide basic information on the authors,
abstract, development and distribution institutions, purpose of development, and the availability of peer
review information, documentation, verification/validation information, and literature citations for 92
unsaturated zone models.
Clinton W. Hall
Director
Robert S. Kerr Environmental
Research Laboratory
in
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ABSTRACT
The present report contains the result of research and information processing activities supporting
evaluation of the capabilities of various unsaturated zone flow and transport models in predicting the
movement of hazardous chemicals through soils to ground water. It provides an overview of major types
of models applicable to problems in the unsaturated zone of the subsurface. As chemical transport in soils
is often driven by the movement of water, both flow and chemical transport models are included.
The review of models has been based on information gathered by the IGWMC through research
and interviews on an on-going basis since 1978. To manage the rapidly growing amount of information,
IGWMC maintains a descriptive model information system, MARS (Model Annotation Search and Retrieval
System). Detailed information on the reviewed models is presented in a series of tables, preceded by an
introduction on model classification, the principal characteristics of the described model types, and model
selection issues.
IV
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BACKGROUND AND REPORT ORGANIZATION
EPA's R.S. Kerr Environmental Research Laboratory (RSKERL) Ada, Oklahoma and Environmental
Research Laboratory (ERL) Athens, Georgia, on request of EPA/OERR, have initiated a project to evaluate
how well various unsaturated zone flow and transport models can predict the movement of hazardous
chemicals through soils to ground water. The project, referred to in this report as 'EPA-project', is divided
in three components: 1) to identify available unsaturated/vadose zone models; 2) to collect and assimilate
test data sets for model evaluation; and 3) to conduct sensitivity and evaluation tests.
The work assigned to the International Ground Water Modeling Center (IGWMC), referred to as
'IGWMC-project', addresses the issues identified as task 1 of the EPA-project: identifying and collecting
information on available models, and cataloguing this information for use in the selection of models for
evaluation.
The objective of the IGWMC-project was to develop a catalogue of available computer models,
specifically designed to simulate the movement and fate of chemicals in the unsaturated/vadose zone. As
the flow characteristics of the (liquid) water phase have an important influence on the movement of
dissolved chemicals in the subsurface, the study has focussed on models or combinations of models that
handle both flow and transport processes.
Additional analysis for this catalogue has focussed on the scenarios the models are designed to
simulate through the incorporation of initial and boundary conditions and source and sink terms.
The catalogue, presented in Appendix 1 through Appendix 7, includes information on each model's
author and institution of development, the code custodian, level of documentation, verification and peer
review, and if it is proprietary or in the public domain. Model description comprises the model name,
acronym, and an abstract describing its purpose, the processes it handles, the general mathematical
method employed, and other major characteristics. Moreover, the catalogue includes information on media
conditions, flow and fluid conditions, and type of boundary conditions handled by the model.
Finally, guidance is presented for the selection of models to be used in task 3 of the EPA-project,
a detailed evaluation of selected models.
The author is grateful to Nicholas J. Kiusalaas, graduate student at the Colorado School of Mines,
for his assistance in collecting and processing model information.
Paul K.M. van der Heijde
Golden, Colorado
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CONTENTS
Foreword iii
Abstract iv
Background and Report Organization v
1. MODELING IN THE UNSATURATED ZONE 1
1.1. Introduction 1
1.2. The Unsaturated Zone 2
1.3. Modeling Transport and Fate of Contaminants in the Unsaturated Zone 2
1.4. Flow Processes in the Unsaturated Zone 6
1.5. Boundary Conditions for Unsaturated Flow 7
1.6. Modeling Sources of Subsurface Pollution 8
1.7. Analytical and Numerical Solutions 9
1.8. Data Requirements 11
2. IDENTIFICATION OF MODELS 13
2.1. Procedures 13
2.2. Model Information System 13
3. MODEL SELECTION 16
3.1. Selection Process 16
3.2. Reliability, Usability and Other Considerations 18
4. CONCLUDING STATEMENT 23
5. REFERENCES 25
APPENDICES
1. Cross-reference Table for Unsaturated Zone Models
2. Flow in the Unsaturated Zone
3. Flow and Solute Transport in the Unsaturated Zone
4. Solute Transport in the Unsaturated Zone (requiring given head distribution)
5. Flow and Heat Transport in the Unsaturated Zone
6. Flow, Solute Transport and Heat Transport in the Unsaturated Zone
7. Parameter Estimation for Flow and Transport in the Unsaturated Zone
8. List of Input Requirements for Selected Unsaturated Zone Models
9. Checklist for MARS Model Annotation
vii
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1. MODELING IN THE UNSATURATED ZONE
1.1. INTRODUCTION
Until the early 1970's, modeling flow and transport through the unsaturated zone focused primarily
on agricultural problems related to irrigation, drainage, and the application of fertilizers and pesticides.
Since, such modeling has expanded to other type of problems due to increased public interest in solving
ground-water pollution problems.
Pollution of subsurface water is typically described in terms of chemical composition. This chemical
composition, often referred to as "water quality," is the result of natural processes and human intervention,
either by introducing chemical compounds directly into the subsurface, or indirectly by modifying the effects
of natural processes on the system. Although human intervention in the environment began many centuries
ago, its significant effects on the quality of subsurface water are of recent origin, and in general are restricted
to regions of significantly altered land use, as by urbanization, industrialization, mining, or agriculture. A
major cause of widespread subsurface pollution is the introduction, purposely or accidentally, of solid and
liquid wastes at the surface or in the near-surface soil and deep subsurface strata as a result of such land
use. The introduced liquids and the leachate from solid waste are often highly mobile and chemically
reactive, directly affecting subsurface water quality. It should be noted that in addition to the introduction
of chemical compounds, ground-water pollution may result from the introduction into the natural system of
hazardous biological compounds such as health-affecting bacteria and viruses.
Many contamination problems find their cause at or near the soil surface. Consequently, the
physical and (bio-)chemical behavior of these contaminants in the shallow subsurface is of critical
importance to the development of protection and remediation strategies. Mathematical models, representing
our understanding of such behavior, provide tools useful in assessing the extent of pollution problems and
evaluating means to prevent and remediate them.
In the context of this report, a major issue is determining the effectiveness of ground-water pollution
remediation schemes. The performance of such schemes is generally reviewed in terms of rate of reduction
in contaminant concentrations (either in ground water or in soils), the absolute time needed to reduce
concentrations to regulatory limits, and the cost involved. For example, the Comprehensive Environmental
Response, Compensation, and Liability Act of 1980 (CERCLA or Superfund), and the Superfund Amendments
and Reauthorization Act of 1986 (SARA) require the establishment of soil remediation levels. Designing an
effective remediation scheme requires site-specific knowledge of the influence of a variety of transport and
fate processes on ground-water and soil contaminant levels. Mathematical models and their computer
program representation provide a quantitative framework for assessment of the effectiveness of remediation
designs taking into consideration the site-specific information obtained in the site characterization process.
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Increasingly, detailed understanding and subsequent modeling of the near-surface zone is crucial
in designing effective remediation approaches. At many sites, this near-surface zone is only partially
saturated with water, requiring specially designed mathematical models. This report focuseo on models that
might prove useful in simulating contaminant levels in such partially saturated systems.
1.2. THE UNSATURATED ZONE
The subsurface hydrosphere is divided in various sub-systems or zones. Directly beneath the land
surface is the zone of aeration, or unsaturated zone, which is partially filled with water (or non-aqueous
phase liquids) and gases (mostly air). Other names used to identify the unsaturated zone, or regions where
the pore space is not water-filled, are vadose zone, variably saturated zone, and partially saturated zone.
The unsaturated zone thickness may vary widely in time and space. In wetlands this zone may be absent,
while in arid areas the thickness of this zone can exceed 1000 m [Bouwer, 1978]. The root zone is that part
of the unsaturated zone that supports plant growth. The root zone generally extends to a maximum depth
of 2 m beneath the land surface {Heath, 1983]. Another term often used to describe the shallow subsurface
is 'soil zone', defined as that part of the subsurface subject to soil forming processes. The soil zone
includes the root zone and might extend to a depth of a few meters [Hillel, 1982]. The soil zone is a major
interaction area between the subsurface hydrosphere, the surface hydrosphere, and the biospheric elements
of terrestrial ecosystems on the other side.
The unsaturated zone is almost always underlain by rock layers that are fully saturated with liquids,
primarily water. The volumetric water content of these saturated regions is equal to the porosity. This is
the saturated zone, and the water in it is commonly referred to as ground water. Water in the unsaturated
zone is commonly referred to as soil water.
At the boundary zone between the unsaturated and saturated zone, the attraction forces between
water and rocks are balanced against the pull of gravity. As a result, the smaller pores are water-saturated
while the larger pores contain both water and air. This boundary area between ground water and soil water
is known as the capillary fringe. It is bounded at the bottom by the water table or the phreatic surface, the
surface where the fluid pressure equals atmospheric pressure [Bear 1979].
1.3. MODELING TRANSPORT AND FATE OF CONTAMINANTS IN THE UNSATURATED ZONE
Modeling contaminant behavior in the unsaturated zone is generally aimed to address such issues
as [NRC, 1990]:
Determining the arrival time of a contaminant at a certain depth; this requires a prediction
of the travel time for the contaminant. Examples of depths of interest are the bottom of the
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root zone, the bottom of the treatment zone of a hazardous waste land treatment system
facility, or the water table.
Predicting the amount of the surface-applied (or spilled) contaminant which might arrive at
the depth of interest within a certain time (or mass flux passing this depth); this requires
assessment of the transport, (temporary) retention, transformation and degradation (fate)
of the contaminant.
Predicting the concentration distribution or the contaminant mass flux In the unsaturated
zone (in both the aqueous and solid phases) at a particular time, or their changes over
time.
The latter purpose is of specific interest to this study as it relates to predicting the amount of
hazardous constituents remaining in the soil following a soil remediation, or due to natural processes.
Contaminating chemicals may leave the soil zone by leaching downwards to the water table, by
volatilization and escape to the atmosphere, by (bio-)chemical transformation or degradation, and by plant
uptake [Jury and Valentine, 1986]. Leaching constitutes mass flow of a chemical constituent and is the
product of water flux and dissolved chemical concentration. Mass flow is dependent on the amount of
applied water, the water application intensity, the saturated hydraulic conductivity of the soil, the chemical
concentration, the adsorption site density, and, indirectly, temperature [Jury and Valentine, 1986]. Soils
provide a strong capacity for adsorbing chemicals and thus removing them from the amount of chemical
subject to mass flux. This is due to the presence of electrically charged clay minerals and organic matter,
and the large surface area of the minerals and humus. Hydrodynamic dispersion is a form of mass flow,
the magnitude of which is subject to the scale over which the water flux is averaged. Volatilization of
chemical vapor to the atmosphere takes place in the vapor phase of the soil and is controlled by chemical,
soil, and atmospheric conditions. Volatilization is dependent on Henry's constant, chemical concentration,
adsorption site density, temperature, water content, wind speed, and water evaporation. Other potentially
important transport processes include vapor and liquid diffusion. Transformation and degradation processes
determine the "fate" of the chemical of concern in the soil. The most important processes include chemical
hydrolysis, biochemical transformations, and oxidation-reduction.
In classifying models generally applied to soil- and ground-water pollution problems, a distinction
can be made between the transport of the contaminants from the point of their introduction into the
subsurface (i.e., contaminant source) to the location of concern (e.g., point of exposure), and the (bio-)
chemical transformations that may occur in the subsurface. A major transport mechanism results from the
hydrodynamic behavior of contaminant carrying fluids or fluid phases in porous or fractured media. Models
specifically simulating fluid flow are referred to as flow models. Models describing the movement of
dissolved chemicals and their interaction with the soil or rock matrix in terms of concentrations and mass
fluxes are often referred to as contaminant transport models or solute transport models. Furthermore,
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models exist which are primarily concerned with (bio-)chemical transformations in the subsurface, and the
resulting fate of contaminants. The latter type of models may be based on a simple mass balance approach
for the chemical of concern lumping spatial variations in a single value for the parameters of interest (e.g.,
SUMMERS model; U.S. EPA, 1989, pp. 28-29), or it may constitute a set of complex equations describing
the (bio-)chemical reactions of interest including a reaction constant data base. To adequately simulate site-
specific pollution problems and their remediation increasingly combinations of these three model types are
employed (e.g., Yeh et a/., 1993).
The success of a given model depends on the accuracy and efficiency with which the physical and
(bio-)chemical processes controlling the behavior of water and introduced non-aqueous liquids, and the
chemical and biological species they transport, are simulated. The accuracy and efficiency of the simulation,
in turn, depend heavily on the applicability of the assumptions and simplifications adopted in the model, the
availability and accuracy of process information and site characterization data, and on subjective judgments
made by the modeler and management.
As stated, flow models simulate the movement of one or more fluids in porous or fractured rock.
One such fluid is water; the others, if present, can be air or vapors such as methane (in soil) or immiscible
nonaqueous phase liquids (NAPLs; in both fully and partially saturated systems) such as certain solvents,
sometimes having a density distinct from water (LNAPLs, DNAPLs). In the context of this report, only the
flow of water (under unsaturated conditions) is considered. Most flow models are based on a mathematical
formulation which considers the hydraulic system parameters as independent field information and hydraulic
head, fluid pressure or water content and fluid flux as dependent variables. They are used to calculate:
steady-state spatial distribution, changes in time in the spatial distribution, or the temporal distribution at a
particular location of such variables as:
hydraulic head, pressure head (or matric head), and suction head;
saturation or moisture content;
magnitude and direction of flow in terms of flow velocities or water mass fluxes;
flowlines and travel times;
position of infiltration fronts.
Inverse flow models simulate the flow field to calculate the spatial distribution of unknown system
parameters using field or experimental observations on the state variables such as hydraulic head, fluid
pressure, water content and fluid flux. Due to the complexity of the relationships between pressure head,
saturation and hydraulic conductivity, there are no truly inverse models available for flow in partially
saturated porous media.
The dominant parameter affecting flow and contaminant transport in the unsaturated zone is
hydraulic conductivity. Accurate measurements of this parameter are difficult to make and very time-
consuming. Therefor, theoretical methods have been developed to calculate the hydraulic conductivity from
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more easily measured soil water retention data based on statistical pore-size distribution models [van
Genuchten etal., 1991]. The resulting functional relationship between pressure head and volumetric water
content (i.e., soil water retention function) is presented in tabular form or as closed-form analytical solutions
which contain functional parameters that are fitted to observed data. With the soil water retention function
known the unsaturated hydraulic conductivity can be calculated using the model of Mualem [1976]. Models
have been developed to fit mathematical functions to water retention with known hydraulic conductivity or
to water retention and hydraulic conductivity simultaneously [van Genuchten etal., 1991]. These models
may also be used to predict hydraulic conductivity for given soil retention data.
Solute transport models are used to predict movement or displacement, concentrations, and mass
balance components of water-soluble constituents, and to calculate concentrations or radiological doses
of soluble radionuclides [van der Heijde et al., 1988]. To do so, solute transport models incorporate various
relevant physical and chemical processes. Flow is represented in the governing convective(-dispersive)
equation by the flow velocity in the advective transport term. The velocities are also used for the calculation
of the spreading by dispersion. If the velocity field is stationary, it may be either calculated once using an
external flow program or read into the program as observed or interpreted data. If the velocity field (i.e.,
spatial distribution of velocities in terms of direction and magnitude) is dependent on time and/or
concentration, then calculation of velocities at each time step is required, either through an internal flow
simulation module or an external flow model linked by means of input and output files. If a dissolved
contaminant is present in relative high concentrations, changes in its distribution during the simulations
might affect the flow behavior through changes in the fluid density. In that case, coupling of the flow and
solute transport equations occur through an equation of state, resulting in a system of equations which
needs to be solved simultaneously (i.e., iteratively-sequentially [Huyakorn and Finder, 1983]).
Generally, modeling the transformation and fate of chemical constituents is done in one of three
possible ways [van der Heijde et al., 1988]: (1) incorporating simplified transformation or fate formulations
in the equation describing solute transport; (2) formulating a mass-balance approach to (bio-)chemical
transformation and fate; and (3) by coupling separate equations describing the (bio-)chemical processes
with the advective-dispersive transport equation. Including transformation processes in solute transport
models results in so-called nonconservative (i.e., with respect to mass in solution) transport and fate models.
The more complex of these nonconservative transport models may include advective and dispersive
transport, molecular diffusion, adsorption (equilibrium and kinetics based), ion-exchange, radioactive decay,
and (bio-)chemical decay.
In some cases, adequate simulation requires the assessment of the influence of temperature
variations (and other physical properties) on flow, solute transport, transformation and fate. A few highly
specialized multipurpose prediction models can handle combinations of heat and solute transport, and rock
or soil matrix deformation. Generally, these models solve the system of equations in a coupled fashion to
provide for analysis of complex interactions among the various physical, chemical, and biological processes
involved.
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In this report, only models simulating flow of water in the unsaturated zone and transport of
dissolved chemicals in soil water will be discussed. Information on models simulating the flow of non-
aqueous phase liquids (either in conjunction with water or as a separate contaminating fluid or contaminant
transporting fluid) can be found in van der Heijde et a/., [1991], among others.
1.4. FLOW PROCESSES IN THE UNSATURATED ZONE
The mathematical model for flow of water in the subsurface is derived by applying principles of mass
conservation (resulting in the continuity equation) and conservation of momentum (resulting in the equation
of motion, i.e., Darcy's law {Bear, 1979]). The most common governing equation for unsaturated flow is
derived by combining the mass balance principle with Darcy's law, ignoring compressibility effects of matrix,
fluid, and air. The resulting equation, known as Richards' equation, is the basis for many unsaturated zone
models [Bear, 1979; DeJong, 1981; El-Kadi, 1983; Jury et a/., 1991]. The dependence of the hydraulic
properties of partially porous media on the hydraulic head or degree of saturation makes the Richard's
equation nonlinear. The degree of nonlinearity depends on the nature of the relationship between hydraulic
conductivity and hydraulic head or saturation, which is often highly nonlinear [Huyakorn and Finder, 1983].
In general, the state variable for saturated flow is piezometric head or fluid pressure. The flow
equation for the unsaturated zone may be expressed in one of two types of state variables, or a
combination: 1) fluid pressure, hydraulic head, pressure head (i.e., matric head), or suction (i.e., negative
pressure head); and 2) moisture content or saturation. Fluid pressure is related to moisture content through
the soil water characteristic curve or soil moisture retention curve. Often, different curves exist for when the
moisture content in a particular soil increases (i.e., wetting curve) and decreases (i.e., drying curve), a
phenomenon called hysteresis. If hysteresis is important the saturation formulation of the Richard's equation
might be preferable as saturation is less sensitive to hysteresis [Hillel, 1982].
In order to solve the transient flow equation, both initial and boundary conditions are necessary.
Initial conditions consist of given values for the dependent variable throughout the model domain
representing the system's status at the beginning of the simulation. For most models, inclusion of initial
conditions is only needed when transient simulations are performed. Boundary conditions may be any of
three types: specified value for the dependent variable (Dirichlet or first type), specified value for the
derivative of the dependent variable perpendicular to the boundary (Neumann type or second type), and
mixed (Cauchy or third type) conditions. Boundary conditions are specified on the periphery of the modeled
domain, either at the border of the modeled area or at internal boundary locations where responses are fixed
(e.g., fluxes in or out of the system through subsurface irrigation pipes or drains, respectively).
The mathematical formulation and solution of the flow problem in the unsaturated zone require
describing the hydraulic properties of soil, preferably in functional form. Hysteresis usually influences these
functions. However, simulation under hysteresis is difficult due to the existence of an infinite number of
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drying and wetting curves, depending on the wetting-drying history of the soil. Several examples of
algebraic equations to represent the soil water characteristic curves with no hysteresis are available [Brooks
and Corey, 1966; Gardner [1958] as used by Haverkamp et a/., 1977; van Genuchten, 1980].
Another complication is the existence of structural voids such as cracks, root holes and animal
channels, often called macropores or macrochannels [Jury et a/., 1991]. As these macrochannels might
provide important conduits for rapid downward migration of contaminants, for certain field conditions models
might be needed that are able to represent the transport through such macro features as well as through
the porous media.
1.5. BOUNDARY CONDITIONS FOR UNSATURATED FLOW
Solution of the partial-differential equations for unsaturated flow requires the specification of initial
and boundary conditions in terms of the relevant state variable [Bear, 1979]. In many cases it is important
to specify if a drying or wetting process is taking place along the boundary due to hysteresis in the soil
water characteristic curve. The following boundary conditions may be encountered in the unsaturated zone
[Bear, 1979; Bear and Verruijt, 1987]:
Prescribed water content (or piezometric head, pressure, or suction) at all points of the
boundary. This is the Dirichlet boundary condition. For example, such a condition is present
when ponding occurs at the soil surface (under practical circumstances, it might be more
difficult to define this condition for the other state variables). At the phreatic surface, generally
considered the lower boundary of the unsaturated zone, the boundary condition is that of zero
fluid pressure.
Prescribed flux of water. This occurs when water reaches the soil surface at a known rate
(e.g., rainfall and sprinkler irrigation) or when the boundary is impervious to water (i.e., zero
flux). Dependent on the presence or absence of a gravity term in the quantification of the
boundary condition, prescribed flux is either a boundary condition of the third or second kind,
respectively.
Under certain circumstances, the boundary condition at the soil surface may change from a
prescribed flux to a prescribed water content. This is the case when the accretion rate at the surface
exceeds the infiltration capacity of the soil surface. Another boundary flux is evaporation. This boundary
flux is dependent on antecedent soil moisture conditions, and soil moisture related limitations on boundary
flux might develop over time, requiring special measures in the implementation of such conditions in models.
Finally, a third-type boundary condition exists when the soil is covered by a water body, separated from the
soil by a semi-pervious layer (e.g., the bottom of a pond).
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1.6. MODELING SOURCES OF SUBSURFACE POLLUTION
When using models to analyze soil contamination problems, the contamination source must be
adequately described in terms of spatial, chemical, and physical characteristics and temporal behavior. The
spatial definition of the source includes location, depth, and area) extent. Model representation of the source
depends on spatial and temporal characteristics and on the scale of modeling. Typical model
representations of pollution sources include a point source for one-, two- and three-dimensional models, and
a line source, a distributed source of limited extent, and a non-point source of unlimited extent for two- and
three-dimensional models.
The source can be located at the boundary or within the system for which the model is developed,
dependent on the dimensionality of the model among others. Mathematically, contaminant sources can be
simulated as a boundary condition, or through specific, closely connected source terms in the governing
flow and transport equations. Typically, if a source is represented as boundary condition, a third-type
transport boundary condition is chosen.
To represent a source accurately, the location of the source with respect to the model domain needs
to be defined. When the source lies outside or at the edge of the domain it is considered a boundary
source, represented by either a formal boundary condition or by a boundary source/sink term (dependent
on the mathematical formulation of the model). If the modeled domain is the unsaturated zone of the
subsurface, such a source might be an impoundment, surface spill, or waste pile. When the source lies
within the model domain, it is considered an internal source which may only be represented by an internal
source/sink function. Often internal sources are present as a secondary source resulting from temporary
attenuation of contaminants released by a surface source followed by delayed release ("bleeding" [NRC,
1990]) of the contaminant to the water table. If the source is a boundary source represented by a boundary
condition, the model selected needs to facilitate the proper boundary condition (specified concentration,
specified mass flux, or concentration-gradient dependent mass flux).
The extent of the simulated plume is influenced by the choice of the source's spatial dimensions.
The areal extent of the source in relation to the modeling scale determines the spatial character of the
source in the model. In some cases a non-point pollution source for a local scale model is considered a
point pollution source for modeling at a regional scale (e.g., septic tanks, landfills, feedlots).
Another source characteristic important to the modeling process is source history, or expected
behavior in time. The source can be continuous in time, either fluctuating or constant in strength (e.g.,
landfills, impoundments, feedlots), or in the form of a pulse or series of individual, non-overlapping pulses
(e.g., spills, leaching of agro-chemicals during or after a storm).
It should be noted that to correctly represent the source, often, both flow and transport boundary
conditions or flow and transport source terms are involved.
8
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1.7. ANALYTICAL AND NUMERICAL SOLUTIONS
Most mathematical models for the simulation of flow and solute transport in the unsaturated zone
are distributed-parameter models, either deterministic or stochastic [van der Heijde et a/., 79887. Tneir
mathematical framework consists of one or more partial differential equations describing the flow and/or
transport and fate processes, as well as initial and boundary conditions and solution algorithms. Some of
these models assume that the processes active in the system are stochastic in nature or, at least, that the
process variables may be described by probability distributions. In such stochastic models system
responses are characterized by statistical distributions estimated by solving a deterministic governing
equation.
The governing equations for flow and transport in the unsaturated zone are usually solved either
analytically or numerically. Analytical models contain a closed-form or analytical solution of the field
equations subject to specified initial and boundary conditions. To obtain these analytical solutions,
simplifying assumptions have to be made regarding the nature of the soil-water-solute system, geometry,
and external stresses, often limiting their application potential. Because of the complex nature of single and
multi-phase flow in the unsaturated zone and the resulting nonlinearity of the governing equation(s) very few
analytical flow solutions have been published [Bear, 1979]. With respect to transport and fate the situation
is somewhat different. Many one-, two-, and three-dimensional analytical solutions for the classical
convection-dispersion equation exist, often requiring a uniform flow field. Some of these solutions,
specifically one-dimensional solutions, can be used in the unsaturated zone assuming a uniform vertical soil
water flux.
In semi-analytical models, complex analytical solutions are approximated, often using numerical
techniques. In the case of unsaturated flow, semi-analytical solutions may be derived by using analytical
expressions for the relationships between the dependent variables and the hydraulic parameters and
involving numerical integration [Bear, 1979]. Models based on a closed-form solution for either the space
or time domain, and which contain additional numerical approximations for the other domain, are also
considered semi-analytical models. Various quasi-analytical techniques and approximate (analytical)
equations have been developed for simulating infiltration of water in soils [El-Kadi, 1983]. The same holds
true for the one-dimensional transport of solutes [van Genuchten and Alves, 1982].
In numerical models, a discrete solution is obtained in both the space and time domains by using
numerical approximations of the governing partial differential equation. As a result of these approximations
the conservation of mass and accuracy in the prediction variable are not always assured (because of
truncation and round-off errors) and thus needs to be verified for each application. Spatial and temporal
resolution in applying such models is user-defined. If the governing equations are nonlinear, as is the case
in simulating flow in the unsaturated zone, linearization often precedes the matrix solution [Remson et at.,
1971; Huyakorn and Finder, 1983]. Usually, solution of nonlinear equations is achieved employing nonlinear
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matrix methods such as the Picard, Newton-Raphson, and Chord-Slope methods [Huyakorn and Finder,
1983].
The numerical solution techniques used for approximating the spatial components of the governing
flow equations in the unsaturated zone are primarily the finite-difference methods (FD), the integral finite-
difference methods (IFDM), and the Galerkin finite-element method (FE). In most cases, time is
approximated by finite difference techniques resulting in an explicit, (weighted) implicit or fully implicit
solution scheme. A finite-difference solution is obtained by approximating the derivatives of the governing
equation. In the finite-element approach an integral equation is formulated first, followed by the numerical
evaluation of the integrals over the discretized flow or transport domain. The formulation of the solution in
each approach results in a set of algebraic equations which are then solved using direct or iterative matrix
methods. Specific schemes may be required for the constitutive relationships, specifically in the presence
of hysteresis.
There are many numerical considerations in selecting a model for simulation of a particular soil-
water-solute system. Simulating flow in relative wet soils (e.g., nearly saturated conditions and ponding)
requires expression of the Richard's equation in terms of hydraulic head, matric head or suction head,
especially when parts of the modeled soil system become fully saturated. However, application of this form
of the Richard's equation causes significant convergence problems when simulating an infiltration front in
extremely dry soil conditions; in the latter case formulation of Richard's equation should be based on
saturation or mixed pressure-saturation [Huyakorn and Finder, 1983; Celia et a/., 1990]. An advantage of
the mixed form is that it allows the transition from unsaturated to saturated conditions while maintaining
numerical mass conservation Celia etal., 1990). Also, significant mass balance problems might occur when
site-specific conditions result in highly nonlinear model relationships [Celia et a/., 1990].
Other issues that should be addressed in selecting a model for simulating flow in the unsaturated
zone are the possible need for double precision versus single precision variables, the time-stepping
approach incorporated, the definition used for intercell conductance (e.g., harmonic mean versus geometric
mean), and, if present, the way steady-state simulation is achieved (most models do not provide steady-state
flow solutions). Some of the problems one may encounter with specific models (or modeling techniques)
include code limitations on gridding flexibility, numerical problems in zones with high-contrast soil or rock
properties, and inaccuracy and instability in areas where the flow field changes significantly in magnitude
and direction. In some cases, avoiding inaccuracy and instability problems require very small spatial and
temporal increments, making multi-dimensional simulations expensive or even unfeasible. Sometimes, an
adaptive time-stepping scheme is implemented in the computer program to optimize time step requirements.
Typical numerical techniques encountered in solving the convertive-dispersive solute transport
equation in the unsaturated zone are comparable to those employed in simulating solute transport in the
saturated zone and include various finite-difference methods, the integral finite-difference method, various
Galerkin finite-element formulations, and variants of the method of characteristics [Yeh et a/., 1993]. As with
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flow, time is generally approximated by finite difference techniques resulting in an explicit, (weighted) implicit
or fully implicit solution scheme.
Typical problems found in applying traditional finite difference and finite element techniques to
simulate contaminant transport in both the saturated and unsaturated zones include numerical dispersion
and oscillations. Numerical dispersion is referred to when the actual physical dispersion mechanism of the
contaminant transport cannot be distinguished from the front-smearing effects of the computational scheme
[Huyakorn and Finder, 1983]. For the finite-difference method, this problem can be reduced by using the
central difference approximation. Spatial concentrations oscillations (and related overshoot and undershoot)
may occur near a sharp concentration front in an advection-dominated transport system. Remedies for
these problems are found to some extent in the reduction of grid increments or time step size, or by using
upstream weighing for spatial derivatives. The use of weighted differences (combined upstream and central
differences) or the selection of other methods (e.g., the method of characteristics, and the Laplace transform
Galerkin method) significantly reduces the occurrence of these numerical problems.
1.8. DATA REQUIREMENTS
The number and type of parameters required for modeling flow and transport processes in soils
depend on the type of model chosen. These parameters can be divided in control parameters (controlling
the operation of the computer code), discretization data (grid and time stepping), and material parameters.
The material parameters can be grouped in six sets [Jury and Valentine, 1986]: static soil properties, water
transport and retention functions, basic chemical properties, time-dependent parameters, soil adsorption
parameters, and tortuosity functions. Table 1 lists many of the relevant material model parameters. To
illustrate the variety of input requirements for different types of models, appendix 8 lists the input
requirements of four selected unsaturated zone models: RITZ, FLAME/FLASH, MULTIMED, and VS2D/T.
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Table 1. Selected Material Parameters for Row and Transport Parameters in Soils (After Jury and Valentine,
1986)
Static Soil Properties
porosity
bulk density
particle size
specific surface area
organic carbon content
cation exchange capacity
PH
soil temperature
How and Transport Variables and Properties
saturated hydraulic conductivity
saturated water content
matric head-water content function
hydraulic conductivity function
dispersion coefficient or dispersrvity
Basic Chemical Properties
molecular weight
vapor pressure
water solubility
Henry's constant
vapor diffusion coefficient in air
liquid diffusion coefficient in water
octanol-water or oil-water partition
coefficient
half-life or decay rate of compound
hydrolysis rate(s)
Contaminant Source Characteristics
solute concentration of source
solute flux of source
source decay rate
Time dependent parameters
water content
water flux
infiltration rate
evaporation rate
solute concentration
solute flux
solute velocity
air entry pressure head
volatilization flux
Soil Adsorption Parameters
distribution coefficient
isotherm parameters
organic carbon partition coefficient
Tortuosity Functions
vapor diffusion tortuosity
liquid diffusion tortuosity
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2. IDENTIFICATION OF MODELS
2.1. PROCEDURES
To identify existing models for simulation of flow and contaminant transport in the unsaturated
subsurface, a database search and literature review has been conducted. Initially, the database search was
focussed on the MARS model annotation database of the IGWMC, which as of May 1992 contains about
650 descriptions of soil- and ground-water simulation models. Information for the literature review has been
obtained from various sources, including the IGWMC literature collection of more than 3000 titles and about
20 serials, and through interlibrary loan. Additional information was received from the U.S. EPA Center for
Subsurface Modeling Support (CSMoS) located at RSKERL, Ada, Oklahoma.
New information on characterized models as well as information on new models have been added
to the MARS database. This updated database has been used in an early stage of the project to provide
the EPA-project team with an interim overview of identified models. The final report contains descriptions
of models which have been identified after the submittal of the interim report, or which have been recently
released.
After reviewing the model's documentation and other pertinent literature obtained, contact has been
sought with model authors and code custodians to obtain additional information when necessary.
In the process of collecting information for the catalogue, parameter needs and other input
requirements for selected models have been assessed (Appendix 8). An evaluation of eight flow and
transport models applicable to contaminated soil cleanup provided additional direction for this assessment
1C. Pratt, State of Washington, Dept. of Ecology, 1991, personal communication]. Selected models have
been described with respect to the way they handle source characterization (in both time and space),
dimensionality, boundary conditions, and transport and fate processes. Where appropriate, this information
has been added to the abstract or to the remarks for the individual models. Furthermore, this information
has been used to update the MARS check list of code characteristics (Appendix 9).
2.2. MODEL INFORMATION SYSTEM
To be able to select a computer code appropriate for the site- or problem-specific analysis to be
performed, ground-water modelers need to have an overview of available computer codes and their
characteristics. Since its establishment in 1978, IGWMC has been collecting, analyzing, and disseminating
information on ground-water models, first from the Holcomb Research Institute at Butler University,
Indianapolis, Indiana, and since mid-1991 from the Colorado School of Mines, Golden, Colorado. IGWMC
has developed a systematic approach to classify, evaluate and manage descriptive information regarding
ground-water modeling codes for the purpose of model selection. To manage the continuously growing
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amount of information, IGWMC maintains a descriptive model information system, MARS (Model Annotation
Search and Retrieval System) [van der Heijde and Williams, 1989].
Each model is described in an uniform way by a set of annotations describing its purpose, major
hydrological, mathematical and operational characteristics, input requirements, simulative capabilities, level
of documentation, availability, and applicability. A complete model annotation includes comments made by
the model author and IGWMC staff concerning development, testing, quality assurance and use, as well
references of studies using the model and references that are part of the documentation or considered
pertinent to the model. The checklist used by the IGWMC to characterize ground-water models is given in
Appendix 9.
Based on the analysis of the needs for information on ground-water models, five types of potential
use have been identified:
application to field problems in support of policy-making and resource management decisions;
analyzing field and laboratory experiments as part of a research program;
as basis for new model formulations and software development;
in education regarding modeling principles and training in the use of models; and
verification of and comparison with other models.
The content and structure of the database is thus a consequence of a primary objective: identification of
models for any of the above uses.
The IGWMC staff continuously collects and analyzes information on models related to subsurface
flow and transport phenomena. The initial information may come from open literature or from presentations
and discussions at conferences, workshops, and other meetings, or obtained directly from researchers.
Once a model of interest is located, additional information is collected from the research team that
developed the model, and from pertinent literature to enable the IGWMC staff to include the model in the
MARS database. In selecting a model for inclusion in the referral database, special attention is given to the
importance of the model with respect to the kind of questions raised in model-based problem solving, and
to the development status of the model (e.g., research instrument or deliverable versus a generally
applicable, well-tested and documented routine tool).
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To assure consistency in the evaluation of the model information and data entered in the referral
database, a standardized form (MARS data entry form) has been designed. A complete data set annotation
includes comments made by the original development team and the IGWMC staff, as well as bibliographic
references regarding development, theoretical foundation, updating, and use. After detailed evaluation of
the model documentation by the IGWMC staff, data is entered into MARS. Once all the information
describing a model is entered in the referral database, the information is checked for completeness and data
entry errors.
In order to fulfill the growing and changing information needs of users, comprehensive and flexible
procedures for maintaining, updating, and expanding the databases have been adopted. Every few years
the database structure (programs and record structure) and contents are reviewed and revised.
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3. MODEL SELECTION
3.1. SELECTION PROCESS
Based on the objectives of a project and the characteristics of the soil system involved, the need
for and complexity level of mathematical simulation must be determined. If a model is needed, careful code
selection is critical in ensuring an optimal trade-off between effort and result. The result is generally
expressed as the expected effectiveness of the modeling effort in terms of forecast accuracy. The effort is
ultimately represented by the costs. Such costs should not be considered independently from those of field
data acquisition. For proper assessment of modeling cost, such measures as choice between the
development of a new code or the acquisition of an existing code; the implementation, maintenance, and
updating of the code; and the development and maintenance of databases and their interfacing with the
simulation codes, need to be considered.
As code selection is in essence matching a detailed description of the modeling needs with well-
defined characteristics of existing models, selecting an appropriate model requires analysis of both the
modeling needs and the characteristics of existing models. Major elements in evaluating modeling needs
are:
(1) formulation of the management objective to be addressed and the level of analysis sought
(based among others on the sensitivity of the project for incorrect or imprecise answers or risk
involved);
(2) knowledge of the physical system under study; and
(3) analysis of the constraints in human and material resources available for the study.
To select models efficiently, management-oriented criteria need to be developed for evaluating and
accepting models. Such a set of scientific and technical criteria should include:
Trade-offs between costs of running a model (including data acquisition for the required level
of analysis) and accuracy;
A profile of model user and a definition of required user-friendliness;
Accessibility in terms of effort, cost, and restrictions; and
Acceptable temporal and spatial scale and level of aggregation.
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If different problems must be solved, more than one model might be needed, or a model might be
used in more than one capacity. In such cases, the model requirements for each problem posed have to
be clearly defined at the outset of the selection process. To a certain extent this is also true for modeling
the same system in different stages of the project. Often a model is selected in an early stage of a project
to assist in problem scoping and system conceptualization. Limitations in time and resources and in data
availability might initially force the selection of a "simple" model. Growing understanding of the system and
increasing data availability might lead to a need for a succession of models of increasing complexity. In
such cases, flexibility of the candidate model or the availability of a set of integrated models of different
levels of sophistication might become an important selection criterion.
The major model-oriented criteria in model selection are:
(1) that the model is suitable for the intended use;
(2) that the model is reliable; and
(3) that the model can be applied efficiently.
The reliability of a model is defined by the level of quality assurance applied during development,
verification and field testing. A model's efficiency is determined by the availability of its code and
documentation and its usability, portability, modifiability, and economy with respect to human and computer
resources required.
As model credibility is a major problem in model use, special attention should be given in the
selection process to ensure the use of qualified models that have undergone adequate review and testing
according to standardized review and testing procedures [van der Heijde and Elnaway, 1992].
Finally, acceptance of a model for decision-support use should be based on technical and scientific
soundness, user-friendliness, and legal and administrative considerations.
A model's ability to meet management's information needs and its efficiency in obtaining the
answers sought, are important selection criteria. In evaluating a model's applicability to a problem, a good
description of operating characteristics should be accessible. Elements of such a description are given in
Appendix 9.
Although adequate models are available for analysis of single phase flow problems in soils, modeling
contaminant transport and fate in soils is significantly more problematic. Consequently, the use of models
for water quality assessments in soils is generally restricted to conceptual analysis of pollution problems,
to feasibility studies in design and remedial action strategies, and to data acquisition guidance. It should
be noted that considering the uncertainties associated with the parameters of soil systems [Jury, 1986], it
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Is more feasible to determine the probabilities of the time of arrival of a pollution front than the probabilities
of concentration distributions in space or time.
A perfect match rarely exists between desired characteristics and those of available models. Model
selection is partly quantitative and partly qualitative. Many of the selection criteria are subjective or weakly
justified often because there are insufficient data in the selection stage of the project to establish the
importance of certain characteristics of the system to be modeled. If a match is hard to obtain,
reassessment of these criteria and their relative weight in the selection process is necessary. Hence, model
selection is very much an iterative process.
In selecting models for the simulation of transport and fate of contaminants in the unsaturated zone,
all relevant physical and (bio-)chemical processes active in the shallow subsurface need to be considered,
as well as the planned measures to abate the contamination. Few models exist that are so general and all-
encompassing in their design that they can be used for every situation encountered in the field. In selecting
models for this review, it was recognized that a combination of models rather than a single model might be
necessary to achieve the objectives of the user. As the flow regime present in the subsurface has a major
influence on the transport of chemicals, ample attention is given to models that simulate water flow in the
unsaturated zone (Appendix 2) and programs that assist in the determination of hydraulic parameters from
laboratory and field studies (Appendix 7). Furthermore, the report presents models which simulate water
flow and solute transport and fate, either in coupled or uncoupled fashion (Appendix 3), and models which
simulate only solute transport and fate requiring a known flow field (Appendix 4). Finally, models are listed
which either handle flow and heat transport (Appendix 5), or combined flow, solute transport and heat
transport to facilitate the incorporation of the effects of temperature distributions and variations in time on
flow, transport and fate (Appendix 6).
The report does not discuss models which are based on approximate infiltration equations as these
equations are considered less relevant with respect to advective transport of contaminants. A discussion
of such models can be found in El-Kadi [1983]. Also, the report does not discuss models which handle
multi-phase flow (i.e., water and non-aqueous phase liquids). More information on multi-phase flow (and
transport) models can be found in Abriola [1988] and El-Kadi et al. [1991]. The report lists a limited number
of nitrogen/phosphorus transport models. Additional information on such models can be found in Frissel
and van Veen [1981], Iskander [1981], Tanji [1982], De Willegen er al. [1988], and Vachaud er al. [1988].
3.2. RELIABILITY, USABILITY, AND OTHER CONSIDERATIONS
A model's efficiency is determined by the availability of an operational computer code and complete,
well-organized documentation, access to user support, and by its usability, portability, mod if lability, reliability,
and economy. A brief discussion of some of these criteria is given below.
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Availability
A model is defined as available if the program code associated with it can be obtained either as a
compilable source code or as an already compiled run-time version. Available ground-water modeling
software is either public domain and proprietary. In the United States, most models developed by federal
or state agencies or by universities through funding from such agencies are available without restrictions
in use and distribution, and are therefore considered to be in the public domain. The situation in other
countries is often different, with most software having a proprietary status, even if developed with
government support, or its status is not well-defined. In these cases, the computer code can be obtained
or accessed under certain restrictions of use, duplication, and distribution.
Models developed by consultants and private industry are often proprietary. This may also be true
of software developed by some universities and private research institutions. Proprietary codes are in
general protected by copyright law. Although the source codes of some models have appeared in
publications such as textbooks, and are available on tape or diskette from the publisher, their use and
distribution might be restricted by the publication's copyright.
Further restrictions occur when a code includes proprietary third-party software, such as
mathematical or graphic subroutines. For public domain codes, such routines are often external and their
presence on the host-computer is required to run the program successfully.
Between public domain and proprietary software is a grey area of so-called freeware or user-
supported software. Freeware can be copied and distributed freely, but users are encouraged to support
this type of software development with a voluntary contribution.
It should be noted that for some codes developed with public funding, distribution restrictions are
in force, as might be the case if the software is exported, or when an extensive maintenance and support
facility has been created. In the latter case, restrictions are in force to avoid use of non-quality-assured
versions, to prevent non-endorsed modification of source code, and to facilitate efficient code update
support to a controlled user group.
The major advantage of public domain software is the absence of restrictions regarding its use,
distribution, and modification. However, many public domain models are not as well supported and
maintained as certain commercially distributed proprietary models. Because no mechanism exists to certify
modeling software and their modifications, quality assurance of public domain software is a major problem,
especially if more than one version exists.
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Reliability
Reliability is the capability of a code to: 1) obtain computational results in a mathematically
straightforward fashion (;'.e., converging); 2) reproduce consistent results (i.e., obtain the same results when
executed repeatedly in the same computational environment with the same data set); 3) produce results with
an accuracy determined by resource utilization (e.g., grid scale and time-step size); and 4) produce correct
results (i.e., provide or converge to the correct answer). The reliability of codes should be established by
applying a widely accepted review and testing procedure. Such testing is aimed at removing programming
errors, testing embedded algorithms, and evaluating the operational characteristics of the code through its
execution on carefully selected example data sets (either based on analytical solutions, hypothetical
problems, or existing field or laboratory experiments). It is important to distinguish between code testing
and model testing. Code testing is limited to establishing the correctness of the computer code with respect
to the criteria and requirements for which it is designed and to establish the accuracy and efficiency of the
code within the range of anticipated field conditions. Model testing is more inclusive (and often more
eluding) than code testing, as it represents the final step in determining the validity of the quantitative
relationships derived for the real-world prototype system the model is designed to simulate [van der Heijde
etal., 1988].
A major issue in model use is credibility. A model's credibility is based on its proven reliability and
the extent of its use. Model users and managers often have the greatest confidence in those models most
frequently applied. This notion is reinforced if successful applications are peer-reviewed and published. As
reliability of a program is related to the localized or terminal failures that can occur because of software
errors, it is assumed that most such errors originally present in a widely used program have been detected
and corrected. Yet no program is without programming errors, even after a long history of use and
updating. Some errors will never be detected and do not or only slightly influence the program's utility.
Other errors show up only under exceptional circumstances. Decisions based on the outcome of
simulations will be viable only if the models have undergone adequate review and testing. However, relying
too much on comprehensive verification, extensive field testing (if present), or frequency of model
application may exclude certain well-designed and documented models, even those most efficient for solving
the problem at hand.
Extent of Model Use
A model used by a large number of people demonstrates significant user confidence. Extensive use
often reflects the model's applicability to different types of ground-water systems and to various
management questions. It might also imply that the model is relatively easy to use. Finally, if a model has
a large user base, many opportunities exist to discuss particular applications with knowledgeable colleagues.
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Efficiency
Model efficiency is defined as the ratio between the accuracy obtained and the level of effort, in
terms of human and computer resources, to reach that accuracy. A model's efficiency can be established
by performance testing of the computer code and comparing computational results with benchmarks
representative for the range of application environments anticipated (in terms of system schematization,
parameter values, boundary conditions, and system stresses, among others). Establishing actual criteria
such as CPU time, RAM requirements, I/O time, mass storage requirements, and set-uptime measurements
are needed. Reliability and efficiency are the main foci of performance testing of models.
User Support
If a model user has decided to apply a particular model, technical problems may be encountered
in running the model code on the available computer system. Such a difficulty may result from (1)
compatibility problems between the computer on which the model was developed and the model user's
computer; (2) coding errors in the original model; and (3) user errors in data input and model operation.
User-related errors can be reduced by becoming more familiar with the model. Here the user
benefits from good documentation. If, after careful selection of the model, problems in implementation or
execution of the model occur and the documentation does not provide a solution, the user needs help from
someone who knows the code. Such assistance, called model support, cannot replace the need for proper
training in model use; requests for support from model developers may reach such extensive proportions
that model support becomes a consulting service or an on-the-job training activity. This potential is
generally recognized by model developers, but not always by model users.
Usability
Various problems can be encountered when a simulation code is implemented on the user's
computer system. Such difficulties may arise from hardware incompatibilities or coding of user errors in
code installation, data input, or program execution. Programs that facilitate rapid understanding, knowledge
of their operational characteristics, and are easy to use are called user-friendly and defined by usability. In
such programs, emphasis is generally placed on extensive, well-edited documentation, easy input
preparation and execution, and well-structured, informative output. Adequate code support and
maintenance also enhance the code's usability.
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Portability
Programs that can be easily transferred from one computer environment to another are called
portable. To evaluate a program's portability both software and hardware dependency need to be
considered.
Modtfiabllitv
In the course of a computer program's useful life, the user's experiences and changing management
requirements often lead to changes in functional specifications for the software. In addition, scientific
developments, changing computing environments, and the persistence of errors make it necessary to modify
the program. If software is to be used over a period of time, it must be designed so that it can be
continually modified to keep pace with such events. A difficult to modify code is called fragile and lacks
maintainability. Such difficulties may arise from global, program-wide implications of local changes.
If the program needs to be altered to run in a new computer environment, its modifiability is important.
Modifiability is enhanced by working with a well-maintained program language environment which adheres
to established language standards; by using structured, object-oriented programming techniques and
modular program designs; and by the presence of programmer-oriented documentation including program
flow charts, definition of key variables, discussion of data transfer between the subroutines and functions,
description of purpose and structure individual subroutines and functions, and extensive internal
documentation listing the purpose of individual code segments.
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4. CONCLUDING STATEMENT
This report provides a catalogue of close to 100 flow and transport models which may be used for
the simulation of flow and transport processes in the unsaturated zone, among others to determine the
effectiveness of soil remediation schemes. The models considered range from simple mass balance
calculations to sophisticated, multi-dimensional numerical simulators. This report does not pretend be
complete in its listing of appropriate models. Almost every week, the International Ground Water modeling
Center is informed of new computer codes addressing some aspect of fluid flow and contaminant transport
in the subsurface. Moreover, many codes have been developed primarily for research purposes and are
not very accessible. Also, there are many simple models based on mass balance evaluation or analytical
solution of highly simplified systems not presented in this catalogue. An effort has been made to select
those 'simple' models which are either known for their use in an regulatory or enforcement mode, or which
are considered representative for a certain type of models. This report does not discuss multi-fluid flow and
associated transport of contaminants since a considerable amount of research is currently focussed on
understanding and mathematically describing the physics and chemistry of these systems.
There are six categories of models listed, including models for single-fluid flow, coupled and
uncoupled flow and solute and/or heat transport, and solute transport for given pressure head distribution.
Finally, models are listed which provide soil parameters from column experiments on soil samples.
Although adequate models are available for analysis of single phase flow problems in soils, modeling
contaminant transport and fate in soils is significantly more problematic. Consequently, the use of models
for water quality assessments in soils is generally restricted to conceptual analysis of pollution problems,
to feasibility studies in design and remedial action strategies, and to data acquisition guidance. Considering
the uncertainties associated with the parameters of soil systems, it is more feasible to determine the
probabilities of the time of arrival of a pollution front than the probabilities of concentration distributions in
space or time.
In compiling the information for the catalogue, some relevant issues have arisen. In many cases,
model documentation is insufficient to determine the actual implementation of boundary conditions in the
code, or the required detail in discretization in the spatial and temporal domains. Running a model code,
using test problems different than the example problems given in the documentation, might reveal specific
model characteristics (and "tricks" to handle them), accuracy, stability, or execution problems. Furthermore,
there are few models which handle the complete spectrum of unsaturated zone flow and solute transport
conditions encountered in the field. For example, many models encounter problems in simulating steep
infiltration or concentration fronts.
A systematic performance testing procedure for unsaturated zone models should be developed to
address these issues by incorporating test problems and scenarios which document the range of
geometries, parameter values and boundary conditions which the model can handle adequately, and which
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will reveal situations where the model's behavior is suspect or unsatisfactory. This type of testing should
be performed parallel to the kind of testing which uses independently observed systems such as well-
documented, carefully executed field and laboratory experiments.
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Bear, J. 1979. Hydraulics of Groundwater. McGraw-Hill, New York, New York.
Bear, J., and A. Verruijt. 1987. Modelling Groundwater Flow and Pollution: Theory and Applications of
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Bouwer, H. 1978. Groundwater Hydrology. McGraw-Hill, New York, New York.
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Celia, M.A., E.T. Bouloutas, and R.L Zarba. 1990. A General Mass-Conservative Numerical Solution for the
Unsaturated Flow Equation. Water Resources Res., Vol. 26(7), pp. 1483-1496.
DeJong, R. 1981. Soil Water Models: A Review. LRRI Contr. 123. Land Resource Research Inst., Research
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De Willegen, P., L Bergstrom, and R,G, Gerritse. 1988. Leaching Models of the Unsaturated Zone: Their
Potential Use for management and Planning. In: D.G. DeCoursey (ed.), Proceedings of the Internal.
Symp. on Water Quality Modeling of Agricultural Non-Point Sources, Part 1, pp. 105-128. ARS-81,
USDA Agricultural Research Service, Fort Collins, Colorado.
El-Kadi, A.I. 1983. Modeling Infiltration for Water Systems. GWMI 83-09, International Ground Water
Modeling Center, Holcomb Research Institute, Indianapolis, Indiana.
El-Kadi, A.I., O.A. Elnawawy, P. Kobe, and P.K.M. van der Heijde. 1991. Modeling Multiphase Flow and
Transport. GWMI 91-04, Internat. Ground Water Modeling Center, Colorado School of Mines,
Golden, Colorado.
Frissel, M.J., and J.A. van Veen (eds.). 1981. Simulation of Nitrogen Bahaviour of Soil-Plant Systems.
Centre for Agricultural Publishing and Documentation (PUDOC), Wageningen, The Netherlands.
Gardner, W.R. 1958. Some Steady-State Solutions to the Unsaturated Flow Equation with Application to
Evaporation from a Water-Table. Soil Science Vol. 85, pp. 228-232.
25
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Haverkamp, R., M. Vauclin, J. Bouma, P.J. Wierenga, and G. Vachaud. 1977. A Comparison of Numerical
Simulation Models for One-Dimensional Infiltration. Soil Sci. Soc. of Am. Journ., Vol. 41, pp. 285-
294.
Heath, R.C. 1983. Basic Ground-water Hydrology. Water Supply Paper 2220, U.S. Geological Survey,
Reston, Virginia.
Hillel, D. 1982. Introduction to Soil Physics. Academic Press, New York, New York.
Huyakorn, P.S., and G.F. Pinder. 1983. Computational Methods in Subsurface Flow. Academic Press, New
York, New York.
Iskander, I.K. (ed.). 1981. Modeling Wastewater Renovation. John Wiley & Sons. New York, New York.
Jury, W.A. 1986. Spatial Variability of Soil Properties. In: S.C. Hern and S.M. Melancon (eds.), Vadose
Zone Modeling of Organic Pollutants, Lewis Publishers, Inc., Chelsea, Michigan, pp. 245-269.
Jury, W.A., and R.L Valentine. 1986. Transport Mechanisms and Loss Pathways for Chemicals in Soil. In:
S.C. Hem and S.M. Melancon (eds.), Vadose Zone Modeling of Organic Pollutants, Lewis Publishers,
Inc., Chelsea, Michigan, pp. 37-60.
Jury, W.A., W.R. Gardner, and W.H. Gardner. 1991. Soil Physics, Fifth Edition. John Wiley and Sons, Inc.,
New York, New York.
Mualem, Y. 1976. A New Model for Predicting the Hydraulic Conductivity of Unsaturated Porous Media.
Water Resources Res., Vol. 12(3), pp. 513-522.
National Research Council (NRC). 1990. Ground Water Models—Scientific and Regulatory Applications.
National Academy Press, Washington, D.C.
Remson, I., G.M. Hornberger, and F.J. Molz. 1981. Numerical Methods in Subsurface Hydrology. Wiley
Interscience, New York, New York.
Tanji. K.K. 1982. Modeling of the Soil Nitrogen Cycle. In: F.J. Stevenson (ed.), Nitrogen in Agricultural
Soils, pp. 721-772. Agronomy Monograph 22., Am. Soc. of Agronomy, Crop Sc. Soc. of Am., and
Soil Sc. Soc. of Am., Madison, Wisconsin.
U.S. Environmental Protection Agency. 1989. Determining Soil Response Action Levels Based on Potential
Contaminant Migration to Ground Water: A Compendium of Examples. EPA/540/2-89/057, Office
of Emergency and Remedial Response, Washington, D.C.
Vachaud, G., M. Vauclin, and T.M. Addiscott. 1988. Solute Transport in the Unsaturated Zone: A Review
of Models. In: D.G. DeCoursey (ed.), Proceedings of the Internal. Symp. on Water Quality Modeling
26
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of Agricultural Non-Point Sources, Part 1, pp. 81-104. ARS-81, USDA Agricultural Research Service,
Fort Collins, Colorado.
van der Heijde, P.K.M., A.I. El-Kadi, and S.A. Williams. 1988. Groundwater Modeling: An Overview and
Status Report. EPA/600/2-89/028, U.S. Environmental Protection Agency, R.S. Kerr Environmental
Research Lab., Ada, Oklahoma.
van der Heijde, P.K.M., and S.A. Williams. 1989. Design and Operation of the IGWMC Model Information
Database MARS (Model Annotation Search and Retrieval System). GWMI 89-03. Internal. Ground
Water Modeling Center, Colorado School of Mines, Golden, Colorado.
van der Heijde, P.K.M., and O.A. Elnawawy. 1992. Quality Assurance and Quality Control in the
Development and Application of Ground-Water Models. EPA/600/R-93/011, U.S. Environmental
Protection Agency, Ada, Oklahoma.
van Genuchten, M.T. 1980. A Closed-Form Equation for Predicting the Hydraulic Conductivity of
Unsaturated Soils. Soil Sci. Soc. of Am. Journ.. Vol. 44, pp. 892-898.
van Genuchten, M.Th., and W.J. Alves. 1982. Analytical Solutions of the One-Dimensional
Convective-Dispersive Solute Transport Equation. Techn. Bull. 1661, U.S. Dept. of Agriculture,
Riverside, Calif.
van Genuchten, M.Th., F.J. Leij, and S.R. Yates. 1991. The RETC Code for Quantifying the Hydraulic
Functions of Unsaturated Soils. EPA/600/2-91/065, U.S. Environmental Protection Agency, R.S.
Kerr Environmental Research Lab., Ada, Oklahoma.
Yeh, T.-C., R. Srivastava, A. Guzman, and T. Harter. 1993. A Numerical Model for Water Flow and Chemical
Transport in Variably Saturated Porous Media. Ground Water, Vol. 31(4), pp. 634-644.
27
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Appendix 1: Cross-reference Table for Unsaturated Zone Models
MODEL NAME
3DFEMWATER/3DLEWASTE
BIOSOL
CADIL/AGTEHM
CHAIN
CHEMFLO
CHEMRANK
CMIS
CMLS
CREAMS
CTSPAC
DISPEQ/DISPER/PISTON
DRAINMOD
FEMTRAN
FEMWASTE/FECWASTE
FEMWATER/FECWATER
FLAME
FLAMINGO
FLASH
FLO
FLOFIT
FLOTRA
FLOWVEC
FLUMP
FP
GLEAMS
FIRST AUTHOR
Yeh, G.T.
Baek, N.H.
Emerson, C.J
van Genuchten, M.A.
Nofziger, D.L.
Nofziger, D.L
Nofziger, D.L
Nofziger D.L
Knisel, W.G.
Lindstrom, FT.
Fluhler, H.
Skaggs, R.W.
Martinez, M.J.
Yeh, G.T.
Yeh, G.T.
Baca, R.G.
Huyakorn, P.S.
Baca, R.G.
Vanderberg, A.
Kool, J.B.
Sagar, B.
Li, R-M
Narasimhan, T.N.
Su, C.
Leonard, R.A.
IGWMC
KEY
3377
5021
4290
6225
6712
6640
6710
6711
3540
5031
3450/ 3451
1950
4350
3371
3370
5661
4630
5660
1092
5187
3253
4390
122
6170
3541
PAGE
A-3-5
A-3-18
A-3-8
A-4-3
A-3-22
A-3-17
A-3-19
A-3-20
A-3-6
A-6-4
A-3-5
A-3-2
A-4-1
A-4-1
A-2-10
A-4-4
A-3-11
A-5-4
A-2-6
A-7-4
A-6-1
A-2-15
A-2-5
A-7-2
A-3-20
A-1-1
-------
MODEL NAME
GRWATER
GS2
GS3
GTC
HSSWDS
HYDRUS
INFIL
INFGR
LANDFIL
LEACHM
MATTUM
MLSOIL/DFSOIL
MMT-DPRW
MOTIF
MOUSE
MULTIMED
MUST
NEWTMC
NITRO
ONESTEP
PESTAN
PORFLOW-3D
PRZM
PRZMAL
RETC
RITZ
RUSTIC
FIRST AUTHOR
Kashkuli, H.A.
Davis, L.A.
Davis, LA.
Yu, C.
Perrier, E.R.
Kool J.B.
Vauclin, M.
Craig, P.M.
Korfiatis, G.P.
Wagenet, R.J.
Yen, G.T.
Sjoreen, A.L.
Ahlstrom, S.W.
Guvanasen, V.
Pacenka, S.
Salhotra, A.M.
De Laat, P.J.M.
Lindstrom, FT.
Kaluarachchi, J.J.
Kool, J.B.
Enfield, C.G.
Runchal, A.K.
Carsel, R.F.
Wagner, J.
van Genuchten, M.Th.
Nofziger, D.L
IGWMC
KEY
3660
2891
2892
5082
4410
6229
3570
4380
4400
3411
3375
4140
780
4550
6390
5630
1771
5860
5186
3433
6130
3238
4720
5310
6228
6620
4721
PAGE
A-2-13
A-3-3
A-3-3
A-3-18
A-2-16
A-3-33
A-2-12
A-2-14
A-2-15
A-3-23
A-5-3
A-3-24
A-3-2
A-6-3
A-3-22
A-3-29
A-2-6
A-6-6
A-3-26
A-7-1
A-4-2
A-6-5
A-3-15
A-3-30
A-7-5
A-3-16
A-3-28
A-1-2
-------
MODEL NAME
RZWQM
SATURN
SBIR
SEEPV
SEEP/W (PC-SEEP)
SESOIL
SIMGRO
SOHYP
SOIL
SOILMOP
SOILPROP
SOMOF
SPLASHWATER
SUMMERS
SUTRA
SWACROP
SWMS-2D
TARGET-2DU
TARGET-SOU
TDFD1O
TOUGH
TRACR3D
TRANS
TRIPM
TRUST
UNSAT
UNSAT-H
FIRST AUTHOR
DeCoursey, D.G.
Huyakorn, P.S.
Li, R-M
Davis, L.A.
Krahn, J.
Bonazountas, M.
Querner, E.P.
van Genuchten, M.Th.
El-Kadi, A.I.
Ross, D.L
Mishra, S.
Wesseling, J.W.
Milly, P.
Summers, K.
Voss, C.I.
Wesseling, J.G.
Simunek, J.
Moreno, J.L
Moreno, J.L
Slotta, LS.
Pruess, K.
Travis, B.J.
Walker, W.R.
Gureghian, A.B.
Narasimhan, T.N.
Khaleel, R.
Fayer, M.J.
IGWMC
KEY
5850
583
4391
2890
4980
5039
5010
6226
6330
2062
5183
2983
3590
5260
3830
2550
6221
4931
4934
5213
2582
4270
2950
4081
120
6400
4340
PAGE
A-3-31
A-3-1
A-3-9
A-2-9
A-2-17
A-3-12
A-2-17
A-7-3
A-7-2
A-2-8
A-7-3
A-2-10
A-5-3
A-4-3
A-6-1
A-2-8
A-3-31
A-3-24
A-3-25
A-6-6
A-5-1
A-3-7
A-5-2
A-3-7
A-2-2
A-2-18
A-2-13
A-1-3
-------
MODEL NAME
FIRST AUTHOR
IGWMC
KEY
PAGE
UNSAT-1
UNSAT1D
UNSAT2
VADOFT
VADOSE
VAM2D
VAM3D
VIP
VLEACH
VS2D/VS2DT
VSAFT2
VSAFT3
WATERFLO
van Genuchten, M.Th.
Gupta, S.K.
Neuman, S.P.
Huyakorn, P.S.
Sagar, B.
Huyakorn, P.S.
Huyakorn, P.S.
Stevens, O.K.
Turin, J.
Lappala, E.G.
Yeh, T-C.J.
Yeh, T-C.J.
Nofziger, D.L.
3431
2071
21
4693
3234
4690
4691
5681
5690
4570
5220
5221
6630
A-2-11
A-2-7
A-2-1
A-3-26
A-6-1
A-3-14
A-3-14
A-3-30
A-4-5
A-3-10
A-3-27
A-3-27
A-2-16
A-1-4
-------
Appendix 2: Flow in the Unsaturated Zone
IGWMC Key: 21 Model Name: UNSAT2
Authors: Neuman, S.P., R. A. Feddes, and E. Bresler.
Institution of Model Development: Dept. of Hydrology and Water Resources
University of Arizona, Tucson, AZ 85721
Code Custodian: S.P. Neuman
Dept. of Hydrology and Water Resources
University of Arizona, Tucson, AZ 85721
Abstract:
UNSAT2 is a two-dimensional finite element model for horizontal, vertical, or axisymmetric simulation of
transient flow in a variably saturated, nonunrform anisotropic porous medium. The governing equation is
the Richard's equation expressed in terms of pressure head. Boundary conditions included are Dirichlet and
Neumann, and seepage face. UNSAT2 is capable of simulating infiltration and evaporation as head-
dependent conditions, determined after the fluid pressure is calculated. Evapotranspiration is simulated
through user specified minimum allowed pressure head at the soil surface, maximum evaporation rate, and
soil surface geometric data. User supplied input for simulation of evapotranspiration includes root zone
geometric data, root effectiveness function, plant species wilting pressure, and maximum transpiration rate.
The code can use both quadrilateral and triangular elements. Unsaturated hydraulic properties must be
input in table form; internally, the code uses linear slopes between the data points for interpolation. UNSAT2
has a restart feature for simulating changing boundary conditions. The equation are solved with a band
solver; nonlinearities are handled by a Picard iteration scheme.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications), demonstration/education
Documentation includes: model theory, user's instructions, example problems, program structure
and development, code listing, verification/validation
Verification/validation: verification (analyt. solutions), laboratory data sets, field datasets
(validation), synthetic datasets, code intercomparison
Peer (independent) review: concepts, theory (math), accuracy, documentation
Availability: public domain
Remarks:
An updated and expanded version of the documentation has been prepared by Davis and Neuman
(1983, see references). The computer code of this version is available from:
Division of Waste Management
Office of Nuclear Material Safety and Safeguards
U.S. Nuclear Regulatory Commission
1717 H Street, N. W., Washington, D. C. 20555.
A debate on the representation of the seepage surface in UNSAT2 took place in Water Resources
Research:
Cooley, R.L 1983. Some New Procedures for Numerical Solution of Variably Saturated
Flow Problems. Water Resourc. Res., Vol. 19(5), pp. 1271-1285.
Comment by S.P. Neuman, 1985: Water Resourc. Res., Vol 21 (6), p. 886. and reply by R.L
Cooley. 1985: p. 887-888.
A-2-1
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The performance of UNSAT2 has been compared with FEMWATER, SATURN and TRUST in:
Petersen, D.M., and J.L. Wilson. 1988. Variably Saturated Flow Between Streams and
Aquifers. WRRI 233, New Mexico Water Resources Res. Inst., New Mexico State Univ., Las
Cruces, New Mexico.
A steady-state version of the code is available from Dr. G-T.J. Yeh, Dept. of Hydrology and Water
Resources, University of Arizona, Tuscon, AZ 85721.
References:
Neuman, S. P., R. A. Feddes, and E. Bresler. 1975. Finite Element Analysis of Two-Dimensional
Flow in Soils Considering Water Uptake by Roots; 1. Theory. Soil Soc. Am., Proceed. Vol. 39(2),
pp. 224-230.
Feddes, R. A., S. P. Neuman, and E. Bresler. 1975. Finite Element Analysis of Two-Dimensional
Flow in Soils; II. Field Applications. Soil Sci. Soc. Am., Proceed. Vol. 39(2), pp. 231-237.
Neuman, S. P., R. A. Feddes, and E. Bresler. 1974. Finite Element Simulation of Flow in
Saturated-Unsaturated Soils Considering Water Uptake by Plants. 3rd Ann. Rept. Project
A10-SWC-77, Hydrodynamics and Hydraulics Engineering Lab., Technion, Haifa, Israel.
Davis, L A. and S. P. Neuman. 1983. Documentation and User's Guide: UNSAT2 - Variably
Saturated Flow Model. NUREG/CR -3390, U. S. Nuclear Regulatory Commission, Washington, D.C.
IGWMC Key: 120 Model Name: TRUST
Authors: Narasimhan, T.N.
Institution of Model Development: Lawrence Berkeley Laboratory, Earth Sciences Division, University
of California, Berkeley, CA 94720
Code Custodian: Narasimhan.T.N. (address see above)
Abstract:
TRUST is an integrated finite difference simulator for computation of transient pressure head distributions
in multidimensional, heterogeneous, variably saturated, deformable porous media with complex geometry.
Deformation of the skeleton may be nonelastic. The polygon-based model considers pressure-dependent
density variations. The code calculates internally hydraulic conductivity and fluid mass capacity from
intrinsic permeability, fluid viscosity, fluid density, gravitational constants, void ratio, and compressibilities.
The model allows for hysteresis. The governing equations are solved by an mixed explicit-implicit scheme,
using a pointwise iterative solver. Optionally, a direct solver version is available form the author. This
scheme recognized that regions with small time constants might be weakly coupled, resulting in a highly
effective iterative solution algorithm. All boundaries of the flow domain are handled by a general head
boundary algorithm. Thus, any boundary condition is developed by manipulating a conductance term that
comprises the coefficient of the head differential between interior and exterior boundary node. In addition,
TRUST can handle seepage faces. The recent versions of TRUST allow both harmonic and geometric
means for the conductance term and includes an algorithm for automatically generating successive time step
durations.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications), demonstration/education
A-2-2
-------
Documentation includes: model theory, user's instructions, example problems, program structure
and development, verification/validation
Verification/validation: verification (analyt.solutions), laboratory data sets, code intercomparison
Peer (independent) review: concepts, theory (math), coding, documentation, performance
Availability: public domain
Remarks:
The TRUST code can be coupled with the FLUX program (available from the same source) to
generate a velocity field and the program MILTVL to calculate traveltimes and to generate pathlines
and isochrones.
TRUST is based on the TRUMP code originally developed by A. L. Edwards at Lawrence Livermore
Laboratory, Univ. of Calif, Livermore, Calif.
Modifications were made to the code to simulate flow in fractured unsaturated porous media as
discussed in Wang and Narasimhan (1984; see references). These modifications include additional
characteristic curves and relative permeability curves, van Genuchten formulae for matrix blocks,
gamma distribution formulae for discrete fracture grid blocks, hyperbolic characteristic curves of
Pickens, and a new effective area factor. The new version of TRUST uses either the existing efficient
iterative solver or a new direct solution.
DYNAMIX is a code that couples a version of the program TRUMP with the geochemical code
PHREEQE (Narasimhan, White and Tokunaga (1985; see user references).
TRUST-II is an updated version of the TRUST code by Narasimhan (1976) developed for the U.S.
Nuclear Regulatory Commission by Battelle Pacific Northwest Laboratories (Reisenauer et Al. 1982;
see references).
The TRUST code can be coupled with the FLUX program (available from the same source) to
generate a velocity field and program MILTVL to calculate travel times and to generate pathlines and
isochrones.
SOILGEN contains subroutines to calculate soil moisture characteristic curves based on the work
of Haverkamp, van Genuchten, and Brooks and Su. The user supplies laboratory determined
moisture content versus matric potential points. The code minimizes the sum squared error of the
function over the experimental data. Relative hydraulic conductivity functional relationships may be
determined using the Haverkamp function if experimental data is available or a method based on
the Mualem theory if only moisture characteristic curve data is available.
GRIDGEN was developed to facilitate quick grid generation use with TRUST-II and supplies the data
for blocks 4 and 5 of the TRUST-II code.
MLTRAN uses the method of characteristics to solve the advective transport equation with
retardation. This package uses a finite element grid, therefore the original TRUST-II grid must be
transformed by MLTRAN using the user supplied data. This model consists of 6 submodels that
contours potential head, water content, and pressure head, generates a plot of the finite element
mesh, and plots the movement of water and contaminants.
A-2-3
-------
The performance of TRUST has been compared with UNSAT2, FEMWATER, and SATURN in:
Petersen, D.M., and J.L Wilson. 1988. Variably Saturated Flow Between Streams and Aquifers.
WRRI 233, New Mexico Water Resources Res. Inst., New Mexico State Univ., Las Cruces, New
Mexico.
References:
Narasimhan, T.N. and P.A. Witherspoon. 1976. An Integrated Finite Difference Method for Fluid
Flow in Porous Media. Water Resources Research, Vol. 12(1), pp. 57- 64.
Narasimhan, T.N. 1975. A Unified Numerical Model for Saturated-Unsaturated Ground-Water Flow.
Ph. D. Dissertation, University of California, Berkeley, Calif.
Narasimhan, T.N. and P.A. Witherspoon. 1977. Numerical Model for Saturated-Unsaturated Flow
in Deformable Porous Media; I. Theory. Water Resources Research, Vol. 13(3); pp. 657-664.
Narasimhan, T.N., P.A. Witherspoon, and A.L. Edwards. 1978. Numerical Model for
Saturated-Unsaturated Flow in Deformable Porous Media; II. The Algorithm. Water Resources
Research, Vol. 14(2), pp. 255-261.
Narasimhan, T.N., and P.A. Witherspoon. 1978. Numerical Model for Saturated-Unsaturated Flow
in Deformable Porous Media; III. Applications. Water Resources Research, Vol. 14(6), pp.
1017-1034.
Narasimhan, T.N., and W.A. Palen. 1981. Interpretation of a Hydraulic Fracturing Experiment,
Monticello, South Carolina. AGU Geophysical Research Letters, Vol. 8(5), pp. 481-484.
Narasimhan, T.N. 1979. The Significance of the Storage Parameter in Saturated-Unsaturated
Groundwater Flow. Water Resources Research, Vol. 15(3), pp. 569-576.
Reisenauer, A.E., K.T. Key, T.N. Narasimhan, and R.W. Nelson. 1982. TRUST: A Computer Program
for Variably Saturated Flow in Multidimensional, Deformable Media. NUREG/CR-2360, U.S. Nuclear
Regulatory Commission, Washington, D.C.
Wang, J.S.Y., and T.N. Narasimhan. 1984. Hydrologic Mechanisms Governing Fluid Flow in
Partially Saturated Fractured, Porous Tuff at Yucca Mountain. Lawrence Berkeley Laboratory,
University of Calif., Berkeley, Calif.
Narasimhan, T.N., and S.J. Dreiss. 1986. A Numerical Technique for Modeling Transient Flow of
Water to a Soil Water Sampler. Soil Science, Vol. 14(3), pp. 230-236.
McKeon, T.J., S.W. Tyler, D.W. Mayer, and A.E. Reisenauer. 1983. TRUST-II Utility Package: Partially
Saturated Soil Characterization, Grid Generation, and Advective Transport Analysis.
NUREG/CR-3443, U.S. Nuclear Regulatory Commission, Washington, D.C.
A-2-4
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IGWMC Key: 122 Model Name: FLUMP
Authors: Narasimhan, T.N. (1), and S.P. Neuman (2)
Institution of Model Development: (1) See code custodian; (2) University of Arizona, Tucson, Arizona
Code Custodian: T.N. Narasimhan
Lawrence Berkeley Laboratory, Earth Sciences Div.
University of Calif., Berkeley, CA 94720
Abstract:
FLUMP is a finite element program for the computation of steady and nonsteady, two-dimensional areal or
cross-sectional pressure-head distribution in heterogeneous, anisotropic, variably saturated porous media
with complex geometry.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications), demonstration/education
Documentation includes: model theory, user's instructions, example problems, verification/validation
Verification/validation: verification (analyt.solutions)
Peer (independent) review: concepts, theory (math)
Availability: public domain
Remarks:
FLUMP is especially suited for problems with moderate or high saturation. Some stability problems
may be encountered while applying code to desiccated soils.
A version of FLUMP allowing for subsidence due to pumping in a multi-layered aquifer system has
been developed by S.P. Neuman, C. Preller, and T.N. Narasimhan. This code is called FLUMPS
and is annotated under IGWMC-key # 00025.
FLUMP is based on a computer program for temperature distributions in multi-dimensional systems,
originally developed by A.L Edwards, Lawrence Livermore Laboratory, University of California,
Livermore, in 1969. The original code, TRUMP, has been annotated as IGWMC-key # 04030.
References:
Neuman, S.P. and T.N. Narasimhan. 1975. Mixed Explicit-Implicit Iterative Finite Element Scheme
for Diffusion Type Problems; I. Theory. Rept. 4405, Lawrence Berkeley Laboratory (also published
in Internat. J. for Numerical Methods in Engineering).
Narasimhan, T.N., S.P. Neuman, and A.L. Edwards. 1975. Mixed Explicit-Implicit Iterative Finite
Element Scheme for Diffusion-Type Problems; II. Solution Strategy and Examples. Rept. 4406,
Lawrence Berkeley Laboratory, Berkeley, Calif, (also published in Internat. J. for Numerical Methods
in Engineering).
Narasimhan, T.N., S.P. Neuman, and P.A. Witherspoon. 1978. Finite Element Method for Subsurface
Hydrology Using a Mixed Explicit-Implicit Iterative Scheme. Water Resources Research, Vol. 14(5),
pp. 863-877.
Neuman, S.P., T.N. Narasimhan, and P.A. Witherspoon. 1976. Application of Mixed Explicit-Implicit
Finite Element Method to Nonlinear Diffusion-Type Problems. In: Proceed. Internat. Conf. on Finite
Elements in Water Resources, Princeton University, Princeton, New Jersey, July 12-16, 1976.
A-2-5
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IGWMC Key: 1092 Model Name: FLO
Authors: Vandenberg, A.
Institution of Model Development: National Hydrology Research Institute
Inland Waters Directorate, Ottawa, Ontario, Canada
Code Custodian: Vandenberg, A.
National Hydrology Research Institute, Inland Waters Directorate
Ottawa, K1A OE7 Ontario, Canada
Abstract:
FLO simulates the elements of the hydrological cycle directly influenced by soil and surface drainage
improvements. Total discharge from a drained plot includes surface runoff, and drain discharge is estimated.
Detailed accounts of unsaturated flow is considered, including capillary forces and evapotranspiration.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications)
Documentation includes: model theory, user's instructions, example problems
Availability: public domain
References:
Vandenberg, A. 1985. A Physical Model of Vertical Infiltration, Drain Discharge and Surface Runoff.
National Hydrology Research Institute, Inland Water Directorate, Ottawa, Canada.
IGWMC Key: 1771 Model Name: MUST (Model for Unsaturated flow above a Shallow water Table)
Authors: De Laat, P.J.M.
Institution of Model Development: International Institute for Hydraulic & Environm. Eng.
Delft, The Netherlands
Code Custodian: De Laat, P.J.M.
International Inst. for Hydraulic & Env. Eng.
Oude Delft 95, Delft, The Netherlands
Abstract:
MUST is a finite difference model which simulates one-dimensional vertical, unsaturated groundwater flow,
evapotranspiration, plant uptake, and interception of precipitation by plants.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications)
Documentation includes: model theory, user's instructions, example problems, program structure
and development, code listing, verification/validation
Verification/validation: verification (analytsolutions), laboratory data sets, field datasets (validation)
Peer (independent) review: concepts, theory (math)
Availability: restricted public domain
Remarks:
MUST is an extensively modified version of the code UNSAT by P.J.M. De Laat. These
modifications especially concern the way evapotranspiration is treated and include interception of
precipitation.
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References:
De Laat, P.J.M. 1985. Must, A Simulation Model for Unsaturated Flow. Report Series No. 16,
Internal. Inst. for Hydraulic and Environm. Eng., Delft, The Netherlands.
De Laat, P.J.M. 1985. Simulation of Evapotranspiration and Sprinkling with MUST. H20, Vol. 18,
pp. 363-367. (in Dutch).
IGWMCKey: 2071 Model Name: UNSAT1D
Authors: Gupta, S.K., C.S. Simmons, F.W. Bond, and C.R. Cole
Institution of Model Development: Battelle Pacific NW Laboratories, Richland, Washington
Code Custodian: Simmons, C.S.
Battelle Pacific NW Laboratories, P.O. Box 999, Richland, WA 99352
Abstract:
UNSAT1D is a fully implicit one-dimensional finite difference model for simulation of transient vertical
unsaturated flow in homogeneous, heterogeneous or layered soil profile. The program simulates infiltration,
vertical seepage, and plant uptake by roots as function of the hydraulic properties of soil, soil layering, root
growth characteristics, evapotranspiration rates, and frequency, rate, and amount of precipitation and/or
irrigation. It can handle boundary conditions related to rain, sprinkler or flood irrigation, or constant head
conditions in the upper boundary. The lower boundary can be the water table, dynamic or quasi-dynamic,
or unit gradient. The model estimates groundwater recharge, irrigation and consumptive use of water, return
flows, etc.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications)
Documentation includes: model theory, user's instructions, example problems, code listing,
verification/validation
Verification/validation: verification (analyt.solutions), code intercomparison
Peer (independent) review: concepts, theory (math), documentation
Availability: early version is public domain; EPRI version is proprietary and available
with license
Remarks:
A version with updated documentation is available from EPRI (Electric Power Research Institute,
P.O. Box 50490, Palo Alto, CA 94303.
References:
Gupta, S.K., K.K. Tanji, D.R. Nielsen, J.W. Biggar, C.S. Simmons, and J.L Maclntyre. 1978. Field
Simulation of Soil-Water Movement with Crop Water Extraction. Water Science and Engineering
Paper No. 4013, Univ. of Calif. Dept. of Land, Air and Water Resources, Davis, Calif.
Bond, F.W., C.R. Cole and P.J. Gutknecht. 1984. Unsaturated Groundwater Flow Model
(UNSAT1D) Computer Code Manual. CS-2434-CCM, Electric Power Research Inst., Palo Alto, Calif.
Battelle Pacific Northwest Lab. 1984. Comparison of Two Groundwater Flow Models - UNSAT1D
and HELP. EPRI CS-3695, Electric Power Research Inst., Palo Alto, Calif.
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IGWMC Key: 2062 Model Name: SOILMOP
Authors: Ross, D.L, and H.J. Morel-Seytoux
Institution of Model Development: Colorado State University
Dept. of Civil Eng., Fort Collins, Colorado
Code Custodian: Morel-Seytoux, H.J.
Colorado State University, Dept. of Civil Eng.
Fort Collins, CO 80523
Abstract:
SOILMOP is an analytical model to predict ponding time, infiltration rate and amount, and water content
profiles under variable rainfall conditions. The model solves a one-dimensional flow equation in a
homogeneous soil. Air phase is also included.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications)
Documentation includes: model theory, user's instructions, example problems, program structure
and development, code listing
Availability: public domain
References:
Ross, D.L. and H.J. Morel-Seytoux. 1982. User's Manual for SOILMOP: A Fortran IV Program for
Prediction of Infiltration and Water Content Profiles Under Variable Rainfall Conditions. Interim
Report for FY1981-1982, DER-82-DLR-HJM45, Dept. of Civil Eng., Colorado State Univ., Fort Collins,
Colorado.
Morel-Seytoux, H.J. 1979. Analytical Results for Predictions of Variable Rainfall Infiltration,
Hydrowar Program, CEP 79-80HJM37, Dept. of Civil Eng., Colorado State Univ., Fort Collins,
Colorado.
IGWMC Key: 2550 Model Name: SWACROP
Author: Wesseling, J.G., P. Kabat, B.J. van den Broek, and R.A. Feddes
Institution of Model Development: Winand Staring Centre
Wageningen, The Netherlands
Code Custodian: Winand Staring Centre, Dept. of Agrohydrology
Wageningen, The Netherlands
Abstract:
SWACROP (Soil WAter and CROP production model) is a transient one-dimensional finite difference model
for simulation of the unsaturated zone, which incorporates water uptake by roots. The soil profile is divided
into several layers (containing one or more compartments of variable thickness) having different physical
properties. The partial differential equation for flow in the unsaturated system is solved using a implicit finite
difference scheme. An explicit linearization of the hydraulic conductivity and soil water capacity is used.
Knowing the initial conditions (i.e. water content or pressure head distribution profile) and top and bottom
boundary conditions, the system of equations for all the compartments is solved for each (variable) timestep
by applying the so-called Thomas tri-diagonal algorithm. The iteration procedure within each timestep allows
calculation of all water balance terms for each time period selected.
For the top boundary condition data on rainfall, potential soil evaporation and potential transpiration are
required. When the soil system remains unsaturated, one of three bottom boundary conditions can be used:
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pressure head, zero flux, or free drainage. When the lower part of the system remains saturated, one can
either give the ground-water level or the flux through the bottom of the system as input. In the latter case
the ground-water level is computed. The rate of vegetation growth, both potential and actual can be
simulated in the crop growth submodel linked to the main water model in a complex dynamic way.
However, both models can easily be run separately.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications)
Documentation includes: model theory, user's instructions, example problems, code listing
Peer (independent) review: concepts, theory (math)
Availability: restricted public domain; purchase
References:
Feddes, R.A., P.J. Kowalik and H. Zaradny. 1978. Simulation of Field Water Use and Crop Yield.
Centre for Agriculture. PuW. and Doc. (PUDOC), Wageningen, The Netherlands.
Belmans, C., J.G. Wesseling and R.A. Feddes. 1981. Simulation Model of the Water Balance of a
Cropped Soil Providing Different Types of Boundary Conditions (SWATRE). Nota 1257, Inst. of Land
and Water Management Research (ICW), Wageningen, The Netherlands.
Belmans, C., J.G. Wesseling and R.A. Feddes. 1983. Simulation Model of the Water Balance of a
Cropped Soil, SWATRE. J. of Hydrology, Vol. 63(3/4), pp. 271-286.
Wesseling, J.G., P. Kabat, B.J. van den Broek and R.A. Feddes. 1989. SWACROP: Simulating the
dynamics of the unsaturated zone and water limited crop production. Winand Staring Centre,
Department of Agrohydrology, Wageningen, The Netherlands.
IGWMC Key: 2890 Model Name: SEEPV
Authors: Davis, L.A.
Institution of Model Development: Water, Waste and Land, Inc.
Fort Collins, Colorado
Code Custodian: Davis, Lyle A.
Water, Waste and Land, Inc.
1311 S. College Avenue, Fort Collins, CO 80524
Abstract:
SEEPV is a transient finite difference model to simulate vertical seepage from a tailings impoundment in
variably saturated flow system; the program takes into consideration the interaction between an
impoundment liner and the underlying aquifer.
Model developed for: general use (e.g. in field applications)
Documentation includes: model theory, user's instructions, code listing,
Verification/validation: verification (analyt.solutions)
Peer (independent) review: concepts, theory (math)
Availability: public domain
References:
Davis, LA. 1980. Computer Analysis of Seepage and Groundwater Response Beneath Tailing
Impoundments. Report Grant NSF/RA-800054, Nat. Science Foundation, Washington, D.C.
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IGWMC Key: 2983 Model Name: SOMOF
Authors: Wesseling, J.W.
Institution of Model Development: Delft Hydraulics Laboratory
Emmeloord, The Netherlands
Code Custodian: Wesseling, J.W.
Delft Hydraulics Laboratory
P.O. Box 152, 8300 AD Emmeloord, The Netherlands
Abstract:
SOMOF is s finite difference model for the simulation of transient unsaturated soil moisture flow in a vertical
profile. The model handles various processes, including infiltration from precipitation, capillary forces,
evapotranspiration, gravity drainage, ponding, and plant uptake.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications)
Documentation includes: model theory, user's instructions, example problems
Availability: proprietary, license
Remarks:
SOMOF has been applied for a verification study of the "Black-Box" model, initially used in the
PAWN (Policy Analysis of the Water Management in The Netherlands) study.
References:
The Soil Moisture Zone in a Physically Based Hydrologic Model (PREDIS). Adv. Water Resources.
IGWMC Key: 3370 Model Name: FEMWATER/FECWATER
Authors: Yeh, G.T., and D.S. Ward
Institution of Model Development: Oak Ridge National Laboratory
Oak Ridge, Tennessee
Code Custodian: G.T. Yeh
Penn State University, Dept. of Civil Eng.
225 Sackett Bldg, University Park, PA 16802
Abstract:
FEMWATER is a two-dimensional finite element model to simulate transient, cross-sectional flow in
saturated-unsaturated anisotropic, heterogeneous porous media. The model is designed to treat both point
sources/sinks and non-point sources/sinks, and to handle a wide variety of non-steady state boundary
conditions, including a moving water-table and seepage faces. It allows three alternative approximations for
the time derivative, has three options for estimating the non-linear matrix, and a direct and an iterative matrix
solution option. Furthermore, the program includes automatic time-step
adjustment and has an option to consider axisymmetric problems.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications)
Documentation includes: model theory, user's instructions, example problems, program structure
and development, code listing, verification/validation
Verification/validation: verification (analyt.solutions), laboratory data sets
Peer (independent) review: concepts, theory (math), documentation
Availability: public domain
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Remarks:
FEMWATER is an extensively modified and expanded version of a finite-element Galerkin model
developed by Reeves and Duguid (1975; see references).
FECWATER is a slightly updated version of the FEMWATER version of 1980. A revised version of
FEMWATER was written by G.T. Yeh (1987; see references)
References:
Yeh, G.T. and D.S. Ward. 1980. FEMWATER: A Finite-Element Model of Water Flow Through
Saturated-Unsaturated Porous Media. ORNL-5567. Oak Ridge National Laboratory, Oak Ridge,
Tennessee.
Yeh. G.T. 1987. FEMWATER: A Finite Element Model of Water Flow through Saturated-Unsaturated
Porous Media First Revision. ORNL 5567/R1, Oak Ridge Nat. Lab., Oak Ridge, Tennessee.
Reeves, M., and J.O. Duguid. 1975. Water Movement through Saturated-Unsaturated Porous
Media: A Finite Element Galerkin Model. ORNL-4927, Oak Ridge National Lab., Oak Ridge,
Tennessee.
Yeh, G.T. and R.H. Strand. 1982. FECWATER: User's Manual of a Finite-Element Code for
Simulating Water Flow Through Saturated-Unsaturated Porous Media. ORNL/TM 7316, Oak Ridge
National Laboratory, Oak Ridge, Tennessee.
Yeh. G.T., 1982. Training Course No. 1: The Implementation of FEMWATER (ORNL-5567)
Computer Program. NUREG/CR-2705, U.S. Nuclear Regulatory Commission, Washington, D.C.
IGWMC Key: 3431 Model Name: UNSAT-1
Author: Van Genuchten, M.Th.
Institution of Model Development: Water Resources Program, Dept. of Civil Eng.
Princeton University, Princeton, New Jersey
Code Custodian: Van Genuchten, M.
USDA Salinity Laboratory
4500 Glenwood Drive, Riverside, CA 92501
Abstract:
UNSAT-1 is a Hermetian finite element solution to the Richards' equation for transient one-dimensional,
variably saturated flow in layered soils. The model can handle both abrupt layering and smoothly changing
profile properties.
Model developed for: research (e.g. hypothesis/theory testing)
Documentation includes: model theory, user's instructions, example problems, code listing,
verification/validation
Verification/validation: verification (analyt.solutions)
Availability: public domain
Remarks:
This model is available from the International Ground Water Modeling Center, Colorado School of
Mines, Golden, CO 80401.
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References:
Van Genuchten, M.Th. 1978. Numerical Solutions of the One-Dimensional Saturated/Unsaturated
Flow Equation. Rept. 78-WR-9, Water Resources Progr., Dept. of Civil Engineering, Princeton
University, Princeton, New Jersey.
IGWMC Key: 3570 Model Name: INFIL
Author: Vauclin, M.
Institution of Model Development: Institute de Mecanique de Grenoble
St. Martin D'Heres, France
Code Custodian: M. Vauclin
Institute de Mecanique de Grenoble
BP 68, 38402 St. Martin D'Heres - Cedex France
Abstract:
INFIL is a finite difference model which solves for ponded infiltration into a deep homogeneous soil. The
model is based on the Philip series solution (1957) of a one-dimensional form of the Richards equation.
Output includes water content profile and amount and rate of infiltration at different simulation times. The
program, which requires the soil properties to be expressed in mathematical form, is designed to
accommodate three different sets of these functions. They include the four parameter function of Vauclin
(1979), the three parameter functions of Brutseart (1966 and 1967), and the two parameter function of
Brooks and Corey (1964). A modified version by A.I. El-Kadi also includes a van Genuchten function (1978).
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications), demonstration/education
Documentation includes: model theory, user's instructions, example problems, code listing,
verification/validation
Verification/validation: verification (analytsolutions), laboratory data sets
Peer (independent) review: concepts, theory (math)
Availability: proprietary, purchase
Remarks:
Both the original FORTRAN and modified BASIC versions are available from the International Ground
Water Modeling Center (IGWMC), Colorado School of Mines, Golden, CO 80401.
References:
El-Kadi, A.I. 1983. INFIL: A Fortran IV Program to Calculate Infiltration Rate and Amount and Water
Content Profile at Different Times. FOS-20, International Ground Water Modeling Center, Holcomb
Research Institute, Indianapolis, Indiana.
Vauclin, M., R. Haverkamp and G. Vachaud. 1979. Resolution Numerique D'une Equation De
Diffusion Non Linearie. Presses Universitaires De Grenoble, Grenoble, France.
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IGWMC Key: 3660 Model Name: GRWATER
Authors: Kashkuli, H.A.
Institution of Model Development: Colorado State University
Dept. of Civil Eng., Fort Collins, Colorado
Code Custodian: Daniel K. Sunada
Dept. of Civil Eng., Colorado State University
Fort Collins, CO 80523
Abstract:
GRWATER is a finite difference model to predict the decline of ground water mounds developed under
recharge in an isotropic, heterogeneous water table aquifer. The model has two modules, one for transient
one-dimensional unsaturated flow above the water table which handles infiltration and evapotranspiration,
and one for transient two-dimensional horizontal saturated flow in the aquifer.
Model developed for: research (e.g. hypothesis/theory testing)
Documentation includes: model theory, user's instructions, example problems, code listing,
verification/validation
Verification/validation: verification (analyt.solutions)
Peer (independent) review: concepts, theory (math)
Availability: public domain
Remarks:
The program GRWATER consists of two subprograms, UNSATF for the unsaturated zone and
LJNKFLO for the water table aquifer. LINKFLO is described under IGWMC-Key 2670
References:
Kashkuli, H.A. 1981. A Numerical Linked Model for the Prediction of the Decline of Groundwater
Mounds Developed under Recharge. Ph.D. Thesis, Colorado State Univ., Fort Collins, Colorado.
IGWMC Key: 4340 Model Name: UNSAT-H
Authors: Fayer, M.J., and G.W. Gee
Institution of Model Development: Battelle Pacific Northwest Laboratory
Richland, Washington
Code Custodian: Fayer, M.J.
Battelle Pacific Northwest Laboratory
P.O. Box 999, Richland, WA 99352
Abstract:
UNSAT-H is a one-dimensional finite difference model for simulation of vertical unsaturated soil moisture
flow. It simulates infiltration, drainage, redistribution, surface evaporation and plant water uptake from soil.
The model's numerical technique is specially designed for arid zones characterized by very dry soils similar
to the Hanford site (Washington).
Model developed for: general use (e.g. in field applications)
Documentation includes: model theory, user's instructions, example problems, program structure
and development, code listing, verification/validation
Verification/validation: verification (analyt.solutions)
Peer (independent) review: concepts, theory (math), documentation
Availability: public domain
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Remarks:
UNSAT-H is based on a computer code that was developed by Gupta et al (1978; see references)
to model soil water movement with concurrent crop water extraction. A version of the Gupta et al.
(1978) code, UNSAT1D (IGWMC key # 2071), was documented by Bond et al. (1984; see
references).
References:
Payer, M.J. and G.W. Gee. 1985. UNSAT-H: An Unsaturated Soil Water Flow Code for Use at the
Hanford Site: Code Documentation. PNL-5585, Battelle Pacific Northwest Lab., Richland, Wash.
Gupta, S.K., K.K. Tanji, D.R. Nielsen, J.W. Biggar, C.S. Simmons, and J.L Maclntyre. 1978. Field
Simulation of Soil-Water Movement with Crop Water Extraction. Water Science and Engineering
Paper No. 4013, Univ. of Calif. Dept. of Land, Air and Water Resources, Davis, Calif.
Bond, F.W., C.R. Cole and P.J. Gutknecht. 1984. Unsaturated Groundwater Flow Model
(UNSAT1D) Computer Code Manual. CS-2434-CCM, Electric Power Research Inst., Palo Alto, Calif.
IGWMC Key: 4380 Model Name: INFGR
Authors: Craig, P.M., and E.G. Davis
Institution of Model Development: University of Tennessee
Knoxville, Tennessee
Code Custodian: Davis, E.C.
Oak Ridge National Lab., Environm. Sciences Div.
Oak Ridge, Tennessee 37830
Abstract:
INFGR is one-dimensional model to estimate the infiltration rate using the Green and Ampt equation. The
compression method is used to estimate infiltration during low rainfall periods. The model works well for
determining infiltration but performs poorly in determining soil moisture content.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications)
Documentation includes: user's instructions, code listing
Availability. public domain
Remarks:
The INFGR has been used in conjunction with FEWA (Oak Ridge National Lab.; see IGWMC Key
# 3373) to estimate groundwater recharge in a pollution problem (Graig and Davis, 1985; see
references).
References:
Craig, P.M. and E.C. Davis. 1985. Application of the Finite Element Groundwater Model FEWA to
the Engineered Test Facilities. Oak Ridge National Lab., Publ. No. 2581, Environmental Sciences
Division, Oak Ridge, Tenn.
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IGWMC Key: 4390 Model Name: FLOWVEC
Authors: Li, R-M., K.G. Eggert, and K.Zachmann
Institution of Model Development: Simons, Li and Associates, Inc.
Fort Collins, Colorado
Code Custodian: Run-Ming Li
Simons, Li and Associates, Inc.
P.O. Box 1816, Fort Collins, CO 80522
Abstract:
FLOWVEC utilizes a vector processor for solving three-dimensional, variably saturated flow problems. The
model employs a finite difference technique in the formulation of the governing equations and a block
implicit scheme in the solution.
Model developed for: research (e.g. hypothesis/theory testing)
Documentation includes: model theory, user's instructions, example problems, program structure
and development, code listing, verification/validation
Verification/validation: verification (analyt.solutions)
Peer (independent) review: concepts, theory (math)
Availability: public domain
References:
U, R-M, K.G. Eggert and K. Zachmann. 1983. Parallel Processor Algorithm for Solving
Three-Dimensional Ground Water Flow Equations. National Science Foundation, Washington, D.C.
IGWMC Key: 4400 Model Name: LANDFIL
Authors: Korfiatis, G.P.
Institution of Model Development: Rutgers University
Civil and Environmental Eng., New Brunswick, New Jersey
Code Custodian: George P. Korfiatis
Stevens Institute of Technology, Department of Civil Engineering
Hoboken, NJ 07030
Abstract:
LANDFIL simulates the movement of moisture through the unsaturated zone using a finite difference solution
for the one-dimensional flow equation. Conditions simulated are pertinent to landfills. Precipitation,
evapotranspiration and redistribution are considered. Both lined and unlined landfills may be simulated.
Model developed for: research (e.g. hypothesis/theory testing)
Documentation includes: model theory, user's instructions, example problems, code listing
Peer (independent) review: concepts, theory (math)
Availability: public domain
References:
Korfiatis, G.P. 1984. Modeling the Moisture Transport through Solid Waste Landfills. PhD Thesis,
Rutgers University, The State University of New Jersey, New Brunswick, New Jersey.
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IGWMC Key: 4410 Model Name: HSSWDS
Authors: Perrier, E.R., and A.C. Gibson
Institution of Model Development: Water Resources Engineering Group Environmental Lab.
U.S. Army Engineer Waterways Experiment Station
Vicksburg, Mississippi 39185
Code Custodian: Landreth, R.E.
Municipal Environmental Research Laboratory
Solid and Hazardous Waste Research Div.
U.S. Environmental Protection Agency
Cincinnati, OH 45268
Abstract:
HSSWDS is a one-dimensional, deterministic, water budget model to estimate, the amount of moisture
percolation through different types of landfill. The model was adapted from the CREAMS model (IGWMC
key # 3540) and includes recharge from precipitation, surface runoff and evapotranspiration.
Model developed for: general use (e.g. in field applications)
Documentation includes: model theory, user's instructions, example problems, code listing
Availability: public domain
References:
Perrier, E.R. and A.C. Gibson. 1982. Hydraulic Simulation of Solid Waste Disposal Sites. Office
of Solid Waste and Emergency Response, U.S. Environmental Protection Agency, Washington, D.C.
IGWMC Key: 6630 Model Name: WATERFLO
Authors: Nofziger, D.L
Institution of Model Development: Univ. of Florida, Soil Science Dept.
Gainesville, Florida
Code Custodian: Dennis Watson, IFAS - Software Support, University of Rorida
Building 664, Room 203, Gainesville, FL 32611
Abstract:
The WATERFLO model is based on a finite difference solution of the one-dimensional nonlinear Richards
equation for simulation of water movement through homogeneous soils. The interactive microcomputer
program can accommodate finite and semi-finite soil systems. It provides for the following boundary
conditions at the soil surface: constant potential, constant flux density, rainfall or sprinkler infiltration rate,
and mixed type (flux and potential boundary condition).
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications), demonstration/education
Documentation includes: model theory, user's instructions, example problems, verification/validation
Verification/validation: verification (analyt. solutions), laboratory data sets, field datasets (validation)
Peer (independent) review: concepts, theory (math)
Availability: public domain
References:
Nofziger, D.L 1985. Interactive Simulation of One-Dimensional Water Movement in Soils: User's
Guide. Circular 675, Software in Soils Science, Florida Coop. Extension Service, Univ. of Florida,
Gainesville, Florida.
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IGWMC Key: 4980 Model Name: SEEP/W (PC-SEEP)
Authors: Krahn, J., D.G. Fredlund, L Lam, and S.L Barbour
Institution of Model Development: Geo-Slope Programming Ltd.
Calgary, Alberta, Canada
Code Custodian: J. Krahn
Geo-Slope Programming Ltd.
7927 Silver Springs Road NW, Calgary, Alberta, Canada T3B 4K4
Abstract:
SEEP/W is an interactive finite element program for simulating steady-state and transient 20 cross-sectional
flow in both the saturated and unsaturated zones. It can simulate surface infiltration and evapotranspiration
and handle internal drains. SEEP/W is designed to analyze seepage through earth dams, watertable
location and fluctuations, and mounding of the watertable underneath a leaking waste pond. The model
computes nodal pore-water pressures, hydraulic heads, velocities, flow directions and flow gradients. It
includes postprocessors for finite element mesh plots, head contours and velocity vector plots. SEEP/W
provides options to use either an in-core or an out-of-core iterative solver for the nonlinear flow equations.
Model developed for: general use (e.g. in field applications)
Documentation includes: model theory, user's instructions, example problems
Availability: proprietary, purchase
Remarks:
SEEP/W consists of three group of programs: 1) data input simulation preprocessor PROMSEEP;
2) main processors SEEPSS (steady-state, in-core solver), SEEPTR (transient and steady-state, in
core solver), and SEEPOC (steady-state, out-of-core solver), and 3) post-processors DOT20 (mesh
plots), DOT21 (contour plots), and DOT22 velocity vector plots).
References:
Krahn, J., D.G. Fredlund, L Lam, and S.L Barbour. 1989. PC-SEEP: A Finite Element Program for
Modelling Seepage. Geo-Slope Programming, Ltd., Calgary, Alberta, Canada.
IGWMC Key: 5010 Model Name: SIMGRO
Authors: Querner, E.P.
Institution of Model Development: Inst. for Land and Water Management Research (ICW)
Wageningen, The Netherlands
Code Custodian: E.P. Querner
Inst. for Land and Water Management Research (ICW)
P.O. Box 35, 6700 AA Wageningen, The Netherlands
Abstract:
SIMGRO (SIMulation of GROundwater flow and surface water levels) simulates flow in the saturated zone,
the unsaturated zone, and a surface water system. The saturated zone model consists of a
quasi-threedimensional finite element model with an implicit calculation scheme. The unsaturated zone is
modeled by means of two reservoirs, one for the root zone and one for the subsoil. The root zone is treated
using a water balance model and includes storage and resulting change in phreatic level, capillary rise,
percolation and evapotranspiration. The surface water system, representing a network of small channels,
is considered as a single reservoir with criteria for water supply, discharge, water level control, and
extraction for sprinkling.
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Model developed for: general use (e.g. in field applications)
Documentation includes: model theory, user's instructions, example problems
Availability: proprietary, purchase
References:
Querner, E.P. 1986. An Integrated Surface and Ground-water Flow Model for the Design and
Operation of Drainage Systems. In: Proceed. Internal. Conf. on Hydraulic Design in Water
Resources Engineering: Land Drainage, Southampton, UK, April 16-18, 1986, pp. 101-108. Report
15, Inst. for Land and Water Management Research (ICW), Wageningen, The Netherlands.
IGWMC Key: 6400 Model Name: UNSAT
Authors: Khaleel, R., and T-C.J. Yeh
Institution of Model Development: New Mexico Inst. of Mining and Technology
Dept. of Geoscience, Socorro, New Mexico
Code Custodian: Khaleel, R.
New Mexico Inst. of Mining and Technology
Dept. of Geoscience, Socorro, NM 87901
Abstract:
UNSAT is a Galerkin finite element model for solving the one-dimensional, transient flow equation in
unsaturated porous media. It estimates the rate of infiltration into soil as well as the moisture distribution
following infiltration. Both differential and cumulative mass balance errors are given to illustrate accuracy
of the numerical scheme.
Model developed for: general use (e.g. in field applications), demonstration/education
Documentation includes: model theory, user's instructions, example problems, program structure
and development, code listing, verification/validation
Verification/validation: verification (analyt.solutions), laboratory data sets
Peer (independent) review: concepts, theory (math)
Availability: public domain
References:
Khaleel, R., and T.-C. Yeh. 1985. A Galerkin Finite Element Program for Simulating Unsaturated
Flow in Porous Media. Ground Water, Vol. 23(1), pp. 90-96.
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Appendix 3: Flow and Solute Transport in the Unsaturated Zone
IGWMC Key: 583 Model Name: SATURN
Authors: Huyakorn, P.S., S.D. Thomas, J.W. Mercer, and B.H. Lester
Institution of Model Development: GeoTrans, Inc., Sterling, Virginia
Code Custodian: David Ward, GeoTrans, Inc.
46050 Manekin Plaza, Suite 100, Sterling, VA 22170
Abstract:
SATURN (SATurated-Unsaturated flow and RadioNuclide transport) is a two-dimensional finite element model
to simulate transient, single phase fluid flow and advective-dispersive transport of radionuclides and other
contaminants In fully or partially saturated, anisotropic, heterogeneous porous media. The flow problem is
solved using the Galerkin method to approximate the governing equation, and either the Picard or
Newton-Raphson iterative techniques to treat material nonlinearities. It uses the upstream-weighted residual
method to treat the transport equation.
Model developed for: general use (e.g. in field applications), demonstration/education
Documentation includes: model theory, user's instructions, example problems, code listing
verification/validation
Verification/validation: verification (analyt.solutions), laboratory data sets, code intercomparison
Peer (independent) review: concepts, theory (math)
Availability: proprietary, license
Remarks:
Nodal coordinates for SATURN may be generated by SATURN itself (for simple rectangular
geometry) or by STRPGN, a separate mesh generator.
References:
Huyakorn, P.S. and S.D. Thomas. 1984. Techniques for Making Finite Elements Competitive in
Modeling Flow in Variably Saturated Porous Media. Water Resources Research, Vol. 20(8), pp.
1099-1115.
Huyakorn, P.S., J.W. Mercer and D.S. Ward. 1985. Finite Element Matrix and Mass Balance
Computational Schemes for Transport in Variably Saturated Porous Media. Water Resources
Research, Vol. 21(3), pp. 346-358.
Huyakorn, P.S., S.D. Thomas, J.W. Mercer, and B.H. Lester. 1983. SATURN: A Finite-Element Model
for Simulating Saturated-Unsaturated Flow and Radioactive Nuclide Transport. Techn. Rept.
Submitted By GeoTrans, Inc. to Electric Power Research Inst., Palo Alto, Calif.
Huyakorn, P.S., V.M. Guvanasen, and T.D. Wadsworth. 1985. MGC-SATURN: Moisture Movement
and Groundwater Components of the SATURN Code. Techn. Report by GeoTrans, Inc. for Electric
Power Research Inst., Palo Alto, Calif.
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IGWMC Key: 780 Model Name: MMT-DPRW
Authors: Ahlstrom, S.W., H.D. Foote, and R.J. Serne
Institution of Model Development: Battelle Pacific NW Laboratories
Richland, Washington
Code Custodian: J.F. Washburn
Battelle Pacific NW Laboratories
P.O. Box 999, Richland, WA 99352
Abstract:
MMT-DPRW is a three-dimensional model for simulation of transient saturated and unsaturated flow and
multi-component mass transport in heterogeneous, anisotropic porous media. The model is based on a
finite difference approximation of flow and advective transport of non-conservative species, and a discrete
particle random walk technique for the simulation of hydrodynamic dispersion.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications)
Documentation includes: model theory, user's instructions, example problems, verification/validation
Verification/validation: verification (analyt.solutions)
Peer (independent) review: concepts, theory (math)
Availability: public domain
Remarks:
Updated one-dimensional version is available as MMT-1D. (see IGWMC Key # 0781).
References:
Ahlstrom, S.W. and H.P. Foote. 1976. Multicomponent Mass Transport Model - Theory and
Implementation (Discrete Parcel Random Walk Version). BNWL-2127, Battelle Pacific NW
Laboratories, Richland. Washington.
PNL 1976. MMT-DPRW Transport Model User's Guide. Internal document, Battelle Pacific NW
Laboratories, Richland, Wash.
Ahlstrom, S.W. and R.G. Baca. 1974. Transport Model User's Manual. BNWL-1716, Battelle Pacific
Northwest Laboratories, Richland, Wash.
IGWMC Key: 1950 Model Name: DRAINMOD
Authors: Skaggs, R.W.
Institution of Model Development: North Carolina State University
Dept. of Biological & Agricultural Engineering
Raleigh, North Carolina
Code Custodian: R.W. Skaggs
North Carolina State University
Dept. of Biological and Agric. Eng.
P.O. Box 7625, Raleigh, NC 27695
Abstract:
DRAINMOD is a model for flow and solute transport in shallow, well-drained unsaturated zones. The water
balance equation includes terms for gas phase moisture, drainage loss, evapotranspiration loss, outflow to
the saturated zone, and infiltration. The model assumes that the soil water content is consistent with fluid
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pressure equilibrium conditions. The resulting transient soil water flux rates are used as input into a Petrov-
Galerkin advective-dispersive transport model for nonreactive solutes. DRAINMOD solves simultaneously
for recharge to the saturated zone, the water table elevation, the equilibrium soil water content distribution,
and an evapotranspiration rate, given climatic conditions on an hourly basis as input. The transport module
requires solute concentration of recharge water, water content distribution, and velocity profiles at different
times.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications), demonstration/education
Documentation includes: model theory, user's instructions, example problems, program structure
and development, code listing
Verification/validation: laboratory data sets
Peer (independent) review: concepts, theory (math)
Availability: public domain
References:
Skaggs, R.W. 1977. Evaluation of Drainage - Water Table Control Systems Using a Water
Management Model. In: Proceed, of the Third National Drainage Symp., ASAE Publication 1-77, pp.
61-68.
Skaggs, R.W. 1978. A Water Management Model for Shallow Water Table Soils. Tech. Rept. No.
134, Water Resources Research Institute of the Univ. of North Carolina, N.C. State Univ., Raleigh,
North Carolina.
Skaggs, R.W. 1980. Combination Surface - Subsurface Drainage Systems for Humid Regions. J.
Irrigation and Drainage Div. ASCE, Vol. 106(IR4), pp. 265-283.
Skaggs, R.W. and J.W. Gilliam. 1981. Effect of Drainage System Design and Operation on Nitrate
Transport. Trans, of the ASAE, Vol. 24(4), pp. 929-934.
Skaggs, R.W., N.R. Fausey and B.H. Nolte. 1981. Water Management Model Evaluation for North
Central Ohio. Trans, of the ASAE, Vol. 24(4), pp. 927-928.
Skaggs, R.W., T. Karvonen, and H.M. Kandil. 1991. Predicting Soil Water Flux in Drained Lands.
Paper presented at Internal. Summer Meeting, Am. Soc. of Agric. Eng., Albuquerque, New Mexico.
Kandil, H., C.T. Miller, and R.W. Skaggs. 1992. Modeling Long-Term Solute Transport in Drained
Unsaturated Zones. Water Resources Res., Vol. 28(10), pp. 2799-2809.
IGWMC Key: 2892 Model Name: GS3
Authors: Davis, LA., and G. Segol
Institution of Model Development: Water, Waste and Land, Inc.
Fort Collins, Colorado
Code Custodian: Lyle Davis
Water, Waste and Land, Inc.
1311 S. College Avenue
Fort Collins, CO 80524
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Abstract:
GS3 is a three-dimensional Galerkin finite element code for analysis of fluid flow and advective-dispersive
nonconservative contaminant transport in partially saturated media. The code is particularly useful for
simulation of anisotropic systems with strata of varying thickness and continuity. This code contains many
of the same features as UNSAT2 (IGWMC Key # 0021) such as the ability to simulate mixed Dirichlet and
Neuman boundary conditions for flow and mass transport (concentration of waste leaving the system
through evaporated water is zero) by specifying minimum surface pressure and maximum infiltration rate,
and seepage faces. However, it will not simulate evapotranspiration by defining a root zone and
corresponding plant species data. Unsaturated hydraulic properties are input in table form (no hysteresis).
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications)
Documentation includes: model theory, user's instructions, example problems, code listing,
verification/validation
Verification/validation: verification (analyt.solutions)
Peer (independent) review: concepts, theory (math), documentation
Availability: public domain
References:
Davis, LA. and G. Segol. 1985. Documentation and User's Guide: GS2 and GS3 - Variably
Saturated Flow and Mass Transport Models. NUREG/CR-3901, U.S. Nuclear Regulatory
Commission, Washington, D.C.
IGWMC Key: 2891 Model Name: GS2
Authors: Davis, LA., and G. Segol
Institution of Model Development: Water, Waste and Land, Inc.
Fort Collins, Colorado
Code Custodian: Lyle Davis
Water, Waste and Land, Inc.
1311 S. College Avenue, Fort Collins, CO 80524
Abstract:
GS2 is a two-dimensional Galerkin finite element code for the analysis of flow and contaminant transport in
partially saturated media. Either vertical or horizontal plane simulation is possible. The transport equation
includes convection, dispersion, radioactive decay, linear equilibrium adsorption and a source/sink term.
Boundary conditions for flow may include constant head and constant flux as well as infiltration and
evaporation. For transport, boundary conditions may be specified as constant concentration or mass flux.
Infiltration and evaporation may occur intermittently. An iterative procedure is used to determine type and
length of seepage face boundary.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications)
Documentation includes: model theory, user's instructions, example problems, code listing,
verif ication/val idation
Verification/validation: verification (analyt.solutions)
Peer (independent) review: concepts, theory (math), documentation
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References:
Davis, LA. and G. Segol. 1985. Documentation and User's Guide: GS2 and GS3 - Variably
Saturated Flow and Mass Transport Models. NUREG/CR-3901, U.S. Nuclear Regulatory
Commission, Washington, D.C..
IGWMC Key: 3377 Model Name: 3DFEMWATER/3DLEWASTE
Authors: Yen, G.T.
Institution of Model Development: Oak Ridge Nat. Lab. Environm. Sciences Div.
Oak Ridge, Tennessee 37831
Code Custodian: G.T. Yeh
Penn State University, Dept. of Civil Eng.
225 Sackett Bldg, University Park, PA 16802
Abstract:
3DFEMWATER is a three-dimensional finite element model for simulation of water steady state and transient
flow through saturated-unsaturated media. The model is designed to handle anisotropic and heterogeneous
geologic media, time-varying distributed and point sources and sinks, a wide variety of boundary conditions,
including a moving water table and seepage faces. There are three options for estimating the nonlinear
matrix, two options for solving the linearized matrix equation, and it includes automatic time step adjustment.
3DLEWASTE is a Langrangian-Eulerian finite element model for simulating advective-dispersive transport of
a non-conservative solute. It can be linked with 3DFEMWATER to obtain velocities from flow simulations.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications)
Documentation includes: model theory, user's instructions, example problems, program structure
and development, code listing, verification/validation
Verification/validation: verification (analyt.solutions), code intercomparison
Peer (independent) review: concepts, theory (math), documentation
Availability: public domain
References:
Yeh, G.T. 1987. 3DFEMWATER: A Three-Dimensional Finite Element Model of Water Flow through
Saturated-Unsaturated Media. ORNL-6386. Oak Ridge National Laboratory, Oak Ridge, Tennessee.
IGWMC Key: 3450/3451 Model Name: DISPEQ/DISPER/PISTON
Authors: Fluhler, H., and W.A. Jury
Institution of Model Development: Swiss Federal Inst. of Forest Research
CH 8903 Birmensdorf, Switzerland
Code Custodian: Huber U. Fluhler
240 Nick Davis Road, Madison, AL 35758
Abstract:
DISPEQ/DISPER/PISTON is a series of three finite difference research models to simulate one-dimensional
transport of reactive solute species through soil columns, including dispersion, instantaneous equilibrium
adsorption (DISPEQ) and rate dependent adsorption (DISPER). PISTON is based on piston type flow
without dispersion.
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Model developed for: research (e.g. hypothesis/theory testing)
Documentation includes: model theory, user's instructions, example problems, code listing
Verification/validation: laboratory data sets
Availability: public domain
References:
Fluhler, H. and W.A. Jury. 1983. Estimating Solute Transport Using Nonlinear, Rate Dependent,
Two-Site Adsorption Models; An Introduction to Use Explicit and Implicit Finite Difference
Schemes. Fortran Program Documentation. Rept. 245, Swiss Federal Institution of Forest
Research, Birmensdorf, Switzerland.
IGWMC Key: 3540 Model Name: CREAMS
Authors: Knisel, W.G.
Institution of Model Development: USDA Agricultural Research Service
Tuscon, Arizona
Code Custodian: Walter G. Knisel
USDA Agricultural Research Service
Southeast Watershed Research Laboratory
P.O. Box 946, Tifton, GA 31793
Abstract:
CREAMS (A field scale model for Chemicals, Runoff, and Erosion from Agricultural Management Systems)
is a general watershed model designed to evaluate non-point source pollution from alternate management
practices for field-size areas. It consists of three main components: hydrology, erosion/sedimentation and
chemistry. The hydrology model handles storm runoff, infiltration, soil water movement (providing amount
of seepage beneath root zone and initial soil water content before a storm), and soil/plant evapotranspiration
between storms. The chemistry model includes a nutrient (nitrogen and phosphorus) submodel and a
pesticide submodel.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications), demonstration/education
Documentation includes: model theory, user's instructions, example problems, verification/validation
Verification/validation: verification (analvt.solutions)
Availability: public domain
Remarks:
CREAMS was developed for evaluation of agricultural management systems and their effects on
non-point pollution potential. CREAMS is the predecessor of GLEAMS (IGWMC Key # 3541).
The USDA Soil Conservation Service released its own version of CREAMS in 1984 (USDA 1984; see
references).
References:
Knisel, W.G. (ed.). 1980. CREAMS: A Field Scale Model for Chemicals, Runoff and Erosion from
Agricultural Management Systems. Conservation Research Report No. 26, United States Dept. of
Agriculture, Tuscon, Arizona.
Knisel, W.G. 1990. CREAMS/GLEAMS: A Development Overview. In: Proceed, of the
CREAMS/GLEAMS Symposium, Univ. of Georgia, Athens, Georgia.
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U.S. Department of Agriculture. 1984. User's Guide for the CREAMS Model: Washington Computer
Center Version. USDA-SCS Engineering Division Technical Release 72. Soil Conservation Service,
Washington, D.C.
Laundre, J.W., 1990. Assessment of CREAMS and ERHYP-II Computer Models for Simulating Soil
Water Movement on the Idaho National Engineering Laboratory. Radiological and Environmental
Sciences Laboratory, U.S. Department of Energy, 46 pp.
IGWMC Key: 4081 Model Name: TRIPM
Authors: Gureghian, A.B.
Institution of Model Development: Office of Nuclear Waste Isolation
Battelle Project Management Div., Columbus, Ohio
Code Custodian: Code custodian
Performance Assessment Dept., Office of Nuclear Waste Isolation,
Battelle Project Management Division
505 King Avenue, Columbus, OH 43201
Abstract:
TRIPM is a two-dimensional finite element model to predict the transport of radionuclides decay chain into
and in a phreatic aquifer. It simulates the simultaneous cross-sectional flow water and the transport of
reacting solutes through saturated and unsaturated porous media. The influence of soil-water pH on the
distribution coefficient is included. Boundary conditions include seepage faces.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications)
Documentation includes: model theory, user's instructions, example problems, program structure
and development, code listing, verification/validation
Verification/validation: verification (analyt.solutions)
Peer (independent) review: concepts, theory (math), coding, documentation
Availability: public domain
References:
Gureghian, A.B. 1983. TRIPM: A Two-Dimensional Finite Element Model for the Simultaneous
Transport of Water and Reacting Solutes through Saturated and Unsaturated Porous Media.
ONWI-465, Off. of Nuclear Waste Isolation, Battelle Project Management Div., Columbus, Ohio.
Gureghian, A.B. 1981. A Two-Dimensional Finite-Element Solution Scheme for the
Saturated-Unsaturated Flow with Applications to Flow through Ditch-Drained Soils. Journ. of
Hydrology, Vol. 50, pp. 1-20.
IGWMC Key: 4270 Model Name: TRACR3D
Authors: Travis, B.J.
Institution of Model Development: Los Alamos National Laboratory
Los Alamos, New Mexico
Code Custodian: Travis, B.J.
Los Alamos National Laboratory, MS-F665
Los Alamos, NM 87545
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Abstract:
TRACR3D is a three-dimensional implicit (for fiow)/semi-implicit (for transport) finite difference model for
simulation of transient two-phase flow of water and air, and of non-conservative multi-component transport
in deformable, heterogeneous, water-saturated or variably-saturated, reactive porous and/or fractured media.
Flow of liquid and gas is coupled using Brooks and Corey expressions for relative hydraulic conductivity of
liquid and gas. Transport processes include advection, dispersion, sorption, and decay. The model can
handle simple steady-state, one-dimensional, single phase problems to complex, transient, two-phase flow
and tracer transport.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications)
Documentation includes: model theory, user's instructions, example problems, program structure
and development, code listing, verification/validation
Verification/validation: verification (analyt.solutions), laboratory data sets
Peer (independent) review: concepts, theory (math)
Availability: public domain
References:
Travis, B. 1984. TRACR3D: A Model of Flow and Transport in Porous/Fractured Media. Los
Alamos National Lab., Report LA-9667-MS, Los Alamos, New Mexico.
IGWMC Key: 4290 Model Name: CADIL/AGTEHM
Authors: Emerson, C.J., B. Thomas, R.J. Luxmoore, and D.M. Hetrick
Institution of Model Development: Oak Ridge National Laboratory
Oak Ridge, Tennessee
Code Custodian: Emerson, C.J.
Oak Ridge National Laboratory, Computer Sciences Department
Oak Ridge, TN 37831
Abstract:
CADIL (Chemical Adsorption and Degradation In Land) is a moisture and chemical species mass balance
model which simulates chemical transport through soils. It includes the processes of deposition, infiltration,
adsorption (Freundlich isotherm) and first-order (bio-)chemical degradation of chemicals. It also simulates
the effect of soil temperature on chemical degradation. Chemical transport in soil water may be either
vertical or lateral. Both macropore and matrix flows of chemicals in soil water are modeled. CADIL couples
to AGTEHM, which in turn calculates soil water transport through the bulk matrix and soil macro-pores.
AGTEHM simulates interception, throughfall, infiltration, soil evaporation, plant transpiration, and surface
runoff.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications)
Documentation includes: model theory, user's instructions, example problems, program structure
and development, code listing, verification/validation
Verification/validation: verification (analyt.solutions)
Peer (independent) review: concepts, theory (math)
Availability: public domain
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Remarks:
The CADIL model is executed as a submodel of the AGTEHM model (Hetrick et al. 1982; see
references; see also IGWMC Key # 3390). It was developed from SCEHM, an earlier soil chemical
model developed by Begovich and Jackson (1975; see references.)
References:
Emerson, C.J.; B. Thomas, Jr. and R.J. Luxmoore. 1984. CADIL: Model Documentation for
Chemical Adsorption and Degradation in Land. ORNL/TM-8972, Oak Ridge National Lab., Oak
Ridge, Tennessee.
Begovich, C.L and D.R. Jackson. 1975. Documentation and Application of SCEHM - A Model for
Soil Chemical Exchange of Heavy Metals. ORNL/NSF/EATC-16, Oak Ridge National Laboratory,
Oak Ridge, Tennessee.
Hetrick, D.M., J.T. Holdeman, and R.J. Luxmoore. 1982. AGTEHM: Documentation of Modifications
to the Terrestrial Ecosystem Hydrology Model (TEHM) for Agricultural Applications. ORNL/TM-7856,
Oak Ridge National Lab., Oak Ridge, Tennessee.
Huff, D.D., R.J. Luxmoore, J.B. Mankin, and C.L. Begovich. 1977. TEHM: A Terrestrial Ecosystem
Hydrology Model. ORNL/NSF/EATC-27, Oak Ridge National Lab., Oak Ridge, Tennessee.
IGWMC Key: 4391 Model Name: SBIR
Authors: Li, R-M.
Institution of Model Development: U.S. Bureau of Reclamation
Washington, D.C.
Code Custodian: Li, Run-Ming
3901 Westerly Place, Suite 101
Newport Beach, CA 92660
Abstract:
SBIR is a three-dimensional finite difference model for simulation of flow and mass transport in a variable
saturated porous medium. A vector processor is used in the solution. Benchmark tests indicated the
relatively high efficiency of the code.
Model developed for: research (e.g. hypothesis/theory testing)
Documentation includes: model theory, user's instructions, example problems, program structure
and development, code listing, verification/validation
Verification/validation: verification (analyt.solutions)
References:
Bureau of Reclamation. 1987. SBIR Phase I Final Report. Modeling Physics and Chemistry of
Contaminant Transport in Three-Dimensional Unsaturated Ground-Water Flow. Final Rept. Contract
4-CR-93-00010. U.S. Dept. of the Interior, Washington, D.C. (NTIS access # PB85-160683).
Li, R-M, K.G. Eggert and K. Zachmann. 1983. Parallel Processor Algorithm for Solving
Three-Dimensional Ground Water Flow Equations. National Science Foundation, Washington, D.C.
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IGWMC Key: 4570 Model Name: VS2D/VS2DT
Authors: Lappala, E.G., R.W. Healy, and E.P. Weeks
Institution of Model Development: U.S. Geological Survey
Denver Federal Center, Lakewood, Colorado
Code Custodian: Weeks, E.P.
U.S. Geological Survey
Box 25046, M.S. 413, Denver Federal Center,
Denver, CO 80225
Abstract:
VS2D is a two-dimensional finite difference simulator for cross-sectional or cylindrical variably saturated flow
in porous media. The model allows consideration of non-linear storage, conductance, and sink terms and
boundary conditions. Processes included are infiltration, evaporation and plant rqot uptake. The program
also handles seepage faces. VS2DT is a solute transport module to be used with VS2D. It is based on a
finite difference approximation of the advection-dispersion equation for a single species. Program options
include first-order decay, equilibrium adsorption described by Freundlich or Langmuir isotherms, and
ion-exchange. Nonlinear storage terms are linearized by an implicit Newton-Raphson method, (see also
remarks).
Nonlinear conductance terms, boundary conditions, and sink terms are linearized implicitly. Relative
hydraulic conductivity is evaluated at cell boundaries by using full upstream weighing, the arithmetic mean,
or the geometric mean of values of adjacent cells. Saturated hydraulic conductivities are evaluated at cell
boundaries by using distance weighted harmonic means. The linearized matrix equations are solved using
the strongly implicit method. Nonlinear conductance and storage coefficients are represented by closed-form
algebraic equations or interpolated from tables.
Nonlinear boundary conditions treated by the code include infiltration, evaporation, and seepage faces.
Extraction by plant roots is included as a nonlinear sink term.
Initial conditions may be input as moisture content or pressure head by blocks defined by row and column,
or in a formatted file by cell. An equilibrium profile may be specified above a user defined free water
surface. Infiltration may be simulated by specified flux nodes, specified pressure nodes, or a ponding
function where the user specifies rainfall rate and ponding height. Evaporation is simulated by a user
defined potential evapotranspiration, pressure potential of the atmosphere, and surface resistance.
Evapotranspiration is simulated through the use of user defined potential evapotranspiration, minimum root
pressure, depth of rooting, and root activity at the bottom of the root zone and land surface. Seepage faces
may also be simulated
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications)
Documentation includes: model theory, user's instructions, example problems, program structure
and development, code listing, verification/validation
Verification/validation: verification (analyt.solutions)
Peer (independent) review: concepts, theory (math), documentation
Availability: public domain, proprietary, purchase
Remarks:
A PC version is available from the International Ground Water Modeling Center (Colorado School
of Mines, Golden, CO 80401), which includes a user interface for data entry and program execution.
It requires Intel 80386 based microcomputer with at least 4M bytes RAM and a math co-processor.
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The computer program VS2D, which simulates water movement through variably saturated porous
media, was published in 1987 (Lappala et Al. 1987; see references). The computer program VS2DT,
which includes both non-linear water flow and solute transport, was released in 1990. It included
a slightly modified version of VS2D (Healy 1990; see references).
References:
Lappala, E.G., R.W. Healy and E.P. Weeks, 1987. Documentation of Computer Program VS2D to
Solve the Equations of Fluid Flow in Variably Saturated Porous Media. Water Resources
Investigations Report 83-4099. U.S. Geological Survey, Denver, Colorado.
Healy, R.W. 1987. Simulation of Trickle Irrigation, an Extension to the U.S. Geological Survey's
Computer Program VS2D. Water Resources Investigations Report 87-4086, U.S Geological Survey,
Denver, Colorado.
Healy, R.W. 1990. Simulation of Solute Transport in Variably Saturated Porous Media with
Supplemental Information on Modifications to the U.S. Geological Survey's Computer Program
VS2D. Water-Resources Investigations Report 90-4025, U.S. Geological Survey, Denver, Colorado.
IGWMC Key: 4630 Model Name: FLAMINGO
Authors: Huyakorn, P.S.
Institution of Model Development: GeoTrans, Inc
Sterling, Virginia
Code Custodian: David Ward
GeoTrans, Inc.
46050 Manekin Plaza, Suite 100, Sterling, VA 22170
Abstract:
FLAMINGO is a three-dimensional upstream weighted finite element model to simulate transient water flow
and solute transport processes in fully- and variably saturated porous media. Transport processes included
are advection, hydrodynamic dispersion, linear equilibrium adsorption and first-order decay. Nonlinearities
due to unsaturated soil properties and atmospheric boundary conditions are treated using Picard iterations.
The model uses a Slice Successive Over Relaxation (SSOR) matrix solution scheme.
Model developed for: general use (e.g. in field applications)
Documentation includes: model theory, user's instructions, example problems, program structure
and development, verification/validation
Verification/validation: verification (analyt.solutions), laboratory data sets
Peer (independent) review: concepts, theory (math)
Availability: proprietary, license
References:
Huyakorn, P.S. and T.D. Wadsworth. 1985. FLAMINGO: A Three-Dimensional Finite Element Code
for Analyzing Water Flow and Solute Transport in Saturated-Unsaturated Porous Media. Techn.
Rept. for U.S. Dept. of Agriculture, Northwest Watershed Research Center, Boise, Idaho, Contract
Nr. 53-3K06-4-82, GeoTrans, Inc., Sterling, Virginia.
Huyakorn, P.S., E.P. Springer, V. Guvanasen, and T.D. Wadsworth. 1986. A Three-Dimensional
Finite Element Model for Simulation of Solute Transport in Variably-Saturated Porous Media. Water
Resources Research, Vol. 22(13), pp. 1790-1808.
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IGWMC Key: 5039 Model Name: SESOIL (Seasonal Soil Compartment Model)
Authors: Bonazountas, M.
Institution of Model Development: Arthur D. Little
Boston, Massachusetts
Code Custodian: David Hetrick
8417 Mecklenburg Court, Knoxville, TN 37923
Abstract:
SESOIL is a user-friendly finite-difference soil compartment model designed for long-term hydrologic,
sediment, and pollutant fate simulations. The model distinguishes three major components, the hydrological
cycle, the sediment cycle and pollutant transport and fate. Elements of the hydrologic cycle included are
rainfall, soil moisture variations, infiltration, exfiltration, surface runoff, evapotranspiration, and groundwater
runoff; simulation of the sediment cycle include sediment washload from storms and sediment resuspension
due to wind; the pollutant fate cycle simulated takes into account advection, diffusion, volatilization,
adsorption and desorption, chemical degradation or decay, biological transformations, hydrolysis,
complexation, and ion exchange.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications)
Documentation includes: model theory, user's instructions, example problems, verification/validation
Verification/validation: verification (analyt.solutions)
Peer (independent) review: concepts, theory (math)
Availability: public domain; some versions are proprietary
Remarks:
SESOIL has undergone testing by a variety of organizations. These efforts have included sensitivity
analysis, comparison with other models, and limited comparison with field data (Bonazountas et Al,
1982; Wagner et Al., 1983; Hetrick, 1984; Hetrick et Al., 1982, 1986; Bicknell et Al., 1984; Kincaid et
Al., 1984; Watson and Brown, 1985; Donigian and Rao, 1986; and Hetrick et Al. 1988a, 1988b; see
references).
SESOIL was incorporated as the soil/land component of the screening level multimedia model,
TOX-SCREEN (Hetrick and McDonald-Boyer, 1984), developed by Oak Ridge National Laboratory,
Oak Ridge, Tennessee for EPA's Office of Toxic Substances.
The comprehensive evaluation of SESOIL by Watson and Brown (1985) uncovered numerous
deficiencies in the original version of the model. Subsequently, SESOIL has been extensively
modified at Oak Ridge National Laboratory to enhance its capabilities. This modified version is
incorporated in the Graphical Exposure Modeling System developed for EPA/OTS (GEMS; see
Kinerson and Hall, 1986). This version will be available from the International Ground Water
Modeling Center, Fall 1992.
References:
Bonazountas, M., J. Wagner, and B. Goodwin. 1982. Evaluation of Seasonal Soil/Groundwater
Pollutant Pathways. Arthur D. Little, Inc., Cambridge, Mass.
Wagner, J., M. Bonazountas, and M. Alsterberg. 1983. Potential Fate of Buried Halogenated
Solvents via SESOIL. Arthur D. Little, Inc., Cambridge, Mass.
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Hetrick, D.M. 1984. Simulation of the Hydrologic Cycle for Watersheds. In: Proceedings of the 9th
IASTED International Conference, San Francisco, Calif.
Hetrick, D.M., J.T. Holdeman, and R.J. Luxmore. 1982. AGTHEM: Documentation of Modifications
to the Terrestrial Ecosystem Model (THEM) for Agricultural Applications. ORNL/TM-7856, Oak
Ridge National Laboratory, Oak Ridge, Tennessee.
Hetrick, D.M., and LM. McDonald-Boyer. 1984. User's Manual for TOX-SCREEN: Multimedia
Screening-Level Program for Assessing Potential Fate of Chemicals Released to the Environment.
ORNL-6041, Oak Ridge National Laboratory, Oak Ridge, Tennessee.
Bicknell, B.R., S.H. Boutwell, and D.B. Watson. 1984. Testing and Evaluation of the TOX-SCREEN
Model. Anderson-Nichols and Co., Palo Alto, Calif.
Kincaid, C.T., J.R. Morey, S.B. Yabusaki, A.R. Felmy, and J.E. Rogers. 1984. Geohydrochemical
Models for Solute Migration, Volume 2: Preliminary Evaluation of Selected Computer Codes for
Modeling Aqueous Solutions and Solute Migration in Soils and Geologic Media. EA-3417, Electric
Power Research Instit, Palo Alto, Calif.
Watson, D.B., and S.M. Brown. 1985. Testing and Evaluation of the SESOIL Model.
Anderson-Nichols and Co., Palo Alto, Calif.
Bonazountas, M. and J.M. Wagner. 1984. "SESOIL" A Seasonal Soil Compartment Model. EPA
Contract No. 68-01-6271, by Arthur D. Little, Cambridge, Mass, for U.S. Environmental Protection
Agency, Office of Toxic Substances, Washington, D.C.
Donigian, Jr., A.S., and P.S.C. Rao. 1986. Overview of Terrestrial Processes and Modeling. In: S.C.
Hern and S.M. Melancon (eds.), Vadose Zone Modeling of Organic Polllutants. Lewis Publishers,
Chelsea, Michigan.
Hetrick, D.M., C.C. Travis, P.S. Shirley, and E.L Etnier. 1986. Model Predictions of Watershed
Hydrologic Components: Comparison and Verification. Water Resourc. Bull., Vol. 22(5), pp.
803-810.
Hetrick, D.M., C.C. Travis, S.K. Leonard, and R.S. Kinerson. I988a. Qualitative Validation of
Pollutant Transport Components of an Unsaturated Soil Zone Model (SESOIL). ORNL/TM-10672,
Oak Ridge National Laboratory, Oak Ridge, Tennessee.
Hetrick, D.M., C.C. Travis, and R.S. Kinerson. 1988b. Comparison of an Unsaturated Soil Zone
Model (SESOIL) Predictions with a Laboratory Leaching Experiment. CONF-881209-1, Oak Ridge
National Lab., Oak Ridge, Tennessee.
Kinerson, R.S., and L Hall. 1986. Graphical Exposure Modeling System (GEMS) User's Guide.
Office of Toxic Substances, U.S. Environmental Protection Agency, Washington, D.C.
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IGWMC Key: 4690 Model Name: VAM2D (Variably saturated Analysis Model in 2 Dimensions)
Authors: Huyakorn, P.S.
Institution of Model Development: HydroGeologic, Inc., Herndon, Virginia
Code Custodian: Jan Kool, HydroGeologic, Inc.
1165 Herndon Parkway, Suite 100, Herndon, VA 22070
Abstract:
VAM2D is a two-dimensional Galerkin finite element model to simulate flow and contaminant transport in
variably saturated porous media. The code can perform simulations in an area! plane, a cross-section, or
an axisymmetric configuration. The highly nonlinear soil moisture relations can be treated using Picard or
Newton-Raphson iterations. The model uses the upstream weighted residual method to treat the
advective-dispersive transport equation with linear or non-linear equilibrium sorption, and first-order
degradation. Cross-sectional unconfined flow problems can be analyzed using a rigorous
unsaturated-saturated modeling approach or an approximate saturated-pseudo unsaturated modeling
approach that does not require user-supplied soil moisture relations.
Model developed for: general use (e.g. in field applications)
Documentation includes: model theory, user's instructions, example problems, verification/validation
Verification/validation: verification (analyt.solutions), code intercomparison
Peer (independent) review: concepts, theory (math)
Availability: proprietary, license
Remarks:
The model VAM2D is a descendant of the formulation used in the SATURN code presented by
Huyakorn et Al (1984, 1985; see references). The VAM2D code has been checked by its authors
against available analytical or semi-analytical solutions and similar numerical codes including
UNSAT2, FEMWATER/FEMWASTE, and SATURN.
References:
Huyakorn, P.S., J.W. Mercer and D.S. Ward. 1985. Finite Element Matrix and Mass Balance
Computational Schemes for Transport in Variably Saturated Porous Media. Water Resources
Research, Vol. 21(3), pp. 346-358.
Huyakorn, P.S. and S.D. Thomas. 1984. Techniques for Making Finite Elements Competitive in
Modeling Flow in Variably Saturated Porous Media. Water Resourc. Res., Vol. 20(8), pp. 1099-1115.
Huyakorn, P.S., et Al. 1987. Finite Element Simulation of Moisture Movement and Solute Transport
in a Large Caisson. In: Modeling Study of Solute Transport in the Unsaturated Zone, NUREG/CR
4515-2, pp. 117-170. U.S. Nuclear Regulatory Commission, Washington, D.C.
IGWMC Key: 4691 Model Name: VAM3D
Authors: Huyakorn, P.S.
Institution of Model Development: HydroGeologic, Inc., Herndon, Virginia
Code Custodian: Jan Kool, HydroGeologic, Inc.
1165 Herndon Parkway, Suite 100, Herndon, VA 22070
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Abstract:
VAM3D (Variably saturated Analysis Model in 3 Dimensions) is a three-dimensional finite-element model for
simulation of flow and contaminant transport in variably saturated porous media. It is capable of
steady-state and transient simulations in an areal plane, a cross-section, an axisymmetric configuration, or
a fully three-dimensional mode using rectangular and triangular prisms. Nonlinearities in the unsaturated
flow equation is solved using Picard iteration. The matrix equations are solved using a slice-successive
over-relaxation scheme or conjugate gradient algorithms. The advective-dispersive transport equation is
solved using upstream weighted procedure. Transport includes linear and Freundlich adsorption isotherms
and first-order degradation. An element mesh generator is available.
Model developed for: general use (e.g. in field applications)
Documentation includes: model theory, user's instructions, example problems, verification/validation
Verification/validation: verification (analyt.solutions), code intercomparison
Peer (independent) review: concepts, theory (math)
Availability: proprietary, license
Remarks:
The formulation used in VAM3D is a descendent of the formulation used in the FLAMINGO code
presented by Huyakorn et Al. (1986; see references). Where possible, VAM3D has been checked
by its authors against available analytical or semi-analytical solutions and similar numerical codes
including UNSAT2, FEMWATER/FEMWAST, SATURN and FLAMINGO.
References:
Huyakorn, P.S., E.P. Springer, V. Guvanasen, and T.D. Wadsworth. 1986. A Three-Dimensional
Finite Element Model for Simulation of Solute Transport in Variably-Saturated Porous Media. Water
Resources Research, Vol. 22(13), pp. 1790-1808.
Huyakorn, P.S., et Al. 1987. Finite Element Simulation of Moisture Movement and Solute Transport
in a Large Caisson. In: Modeling Study of Solute Transport in the Unsaturated Zone, NUREG/CR
4515-2, pp. 117-170. U.S. Nuclear Regulatory Commission, Washington, D.C.
Huyakorn, P.S., J.W. Mercer and D.S. Ward. 1985. Finite Element Matrix and Mass Balance
Computational Schemes for Transport in Variably Saturated Porous Media. Water Resources
Research, Vol. 21(3), pp. 346-358.
IGWMC Key: 4720 Model Name: PRZM
Authors: Carsel, R.F., C.N. Smith, LA. Mulkey, and J.D. Dean
Institution of Model Development: U.S. Environmental Protection Agency
Environmental Research Lab., Athens, Georgia
Code Custodian: R.F. Carsel
U.S. Environmental Protection Agency
Environmental Research Lab., Athens, GA 30613
Abstract:
PRZM (Pesticide Root Zone Model) simulates the vertical movement of pesticides in the unsaturated zone
within and below the root zone. The model consists of hydrologic and chemical transport components to
simulate runoff, erosion, plant uptake, leaching, decay, foliar washoff, and volatilization. Pesticide transport
and fate processes include advection, dispersion, molecular diffusion, and soil sorption. Predictions can be
made for daily, monthly or annual output. A finite difference numerical solution, using a backwards difference
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implicit scheme, is employed. PRZM allows the user to perform dynamic simulations considering pulse
loads, predicting peak events, and estimating time-varying emission or concentration profiles in layered soils.
(see also remarks).
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications), demonstration/education
Documentation includes: model theory, user's instructions, example problems, verification/validation
Verification/validation: verification (analyt.solutions), laboratory data sets
Peer (independent) review: concepts, theory (math), documentation
Availability: public domain
Remarks:
PRZM is a one-dimensional finite difference model which accounts for pesticide fate and transport
in the crop root zone. It includes soil temperature effects, volatilization and vapor phase transport
in soils, irrigation simulation and a method of characteristics algorithm to eliminate numerical
dispersion. PRZM is capable of simulating fate and transport of the parent and up to two daughter
species.
PRZM, VADOFT and SAFTMOD are part of RUSTIC. RUSTIC (MARS Key # 4721) links these models
in order to predict the fate and transport of chemicals to drinking water wells. The codes are linked
together with the aid of a flexible execution supervisor (software user interface) that allows the user
to build models that fit site-specific situations.
Wagner and Ruiz (1986; see IGWMC Key # 5310) designed an aquifer linkage model PRZMAL to
connect PRZM with the analytical three-dimensional model PLUME 3D.
References:
Carsel, R.F., C.N. Smith, LA. Mulkey, J.D. Dean, and P. Jowise. 1984. User's Manual for the
Pesticide Root Zone Model (PRZM), Release 1. EPA-600/3-84-109, U.S. Environmental Protection
Agency, Environmental Research Lab., Athens, Georgia.
Carsel, R.F., LA. Mulkey, M.N. Lorber, and LB. Baskin. 1985. The Pesticide Root Zone Model
(PRZM): A Procedure for Evaluating Pesticide Leaching Threats to Ground Water. Ecological
Modeling, Vol. 30, pp. 49-69.
Donigian, Jr., A.S., and P.S.C. Rao. 1986. Overview of Terrestrial Processes and Modeling. In: S.C.
Hern and S.M. Melancon (eds.), Vadose Zone Modeling of Organic Polllutants. Lewis Publishers,
Chelsea, Michigan.
IGWMC Key: 6620 Model Name: RITZ
Authors: Nofziger, D.L (1) , J.R. Williams (2), and T.E. Short (2)
Institution of Model Development: 1) Oklahoma State University, Stillwater, Oklahoma
2) U.S. EPA, R.S. Kerr Env. Res. Lab., Ada, Oklahoma
Code Custodian: J.R. Williams
Robert S. Kerr Environm. Research Lab.
U.S. Environmental Protection Agency
P.O. Box 1198, Ada, OK 74820
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Abstract:
RITZ (Regulatory and Investigative Treatment Zone model) is an interactive program for simulation of the
movement and fate of hazardous chemicals during land treatment of oily wastes. The model considers a
constant water flux and downward movement of the pollutant with the soil solution (leaching), volatilization
and loss to the atmosphere, and (bio-)chemical degradation. The treatment site modeled consists of a plow
zone and a treatment zone. The model incorporates the influence of oil upon the transport and fate of the
pollutant. As input the model requires the properties of the chemicals and oil in the waste material, the soil
properties of the treatment site, the management practices, and the parameters relevant to the environment
of the site.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications), demonstration/education
Documentation includes: model theory, user's instructions, example problems, verification/validation
Verification/validation: verification (analyt.solutions), laboratory data sets, field datasets (validation)
Peer (independent) review: concepts, theory (math), documentation
Availability: public domain
References:
Nofziger, D.L, J.R. Williams, and T.E. Short. 1988. Interactive Simulation of the Fate of Hazardous
Chemicals During Land Treatment of Oily Wastes: RITZ User's Guide. EPA/600/8-88/001, R.S. Kerr
Env. Research Lab., U.S. Env. Protection Agency, Ada, Oklahoma.
Short, T.E. 1988. Movement of Contaminants from Oily Wastes During Land Treatment. In: Soils
Contaminated by Petroleum: Environmental and Public Health Effects. Proceedings Conf. on
Environm. and Public Health Effects of Petroleum Contaminated Soils, Univ. of Mass., Amherst,
Mass. Oct. 30-31, 1985.
IGWMC Key: 6640 Model Name: CHEMRANK
Authors: Nofziger, D.L, P.S.C. Rao, and A.G. Hornsby
Institution of Model Development: Institute of Food and Agricultural Sciences
University of Florida, Gainesville, Florida
Code Custodian: Institute of Food and Agricultural Sciences
University of Florida, Gainesville, FL 32611
Abstract:
CHEMRANK is an interactive package which utilizes four ranking schemes for screening organic chemicals
relative to their potential to leach into groundwater systems. The schemes are based on rates of chemical
movement or relative rates of mobility and degradation of the chemicals within the vadose zone. Two
schemes use steady state groundwater recharge rates and the other two require daily rainfall and
evaporation data. The latter two schemes rank chemical mobility by travel time in the vadose zone or mass
emission of selected chemicals at some specified depth in the vadose zone.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications), demonstration/education
Documentation includes: model theory, user's instructions, example problems
Availability: public domain
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References:
Nofziger, D.L, P.S.C. Rao, and A.G. Hornsby. 1988. CHEMRANK: Interactive Software for Ranking
the Potential of Organic Chemicals to Contaminate Groundwater. Inst. of Food and Agric.
Sciences, University of Florida, Gainesville, Florida.
IGWMC Key: 5021 Model Name: BIOSOIL
Authors: Baek, N.H.
Institution of Model Development: Rensselaer Polytechnic Institute
Dept. of Environmental Eng.
Troy, New York 12181
Code Custodian: N.H. Baek
Occidental Chemical Corporation, Technology Center
2801 Long Road, Grand Island, NY 14072
Abstract:
The system modeled by BIOSOIL consists of four components: 1) soil water flow to transport a limiting
substrate and a recalcitrant chemical; 2) chemical persistence mitigated by an ultimate removal mechanism
of biodegradation; 3) soil microbial growth enriched by exogenous supply of a limiting substrate; and 4)
substrate availability to support soil microbial growth for the enhancement of chemical removal.
Variable-step and variable order Gear's method is employed as a numerical approximation to solve the set
of four ODE's which result from the transformation of four PDE's via the finite difference method. The
response of the system to different values for such model inputs as substrate concentration, application rate,
and application cycle can be studied.
Model developed for: research (e.g. hypothesis/theory testing)
Documentation includes: model theory, user's instructions, example problems, code listing
Peer (independent) review: concepts, theory (math)
Availability: public domain
References:
Baek, N.H. 1986. A Mathematical Model (BIOSOIL) for the Mitigation of Chemical Persistence by
Microbial Enrichment in the Unsaturated Zone. Ph.D. Thesis, Rensselaer Polytechnic Institute, Troy,
New York.
IGWMC Key: 5028 Model Name: GTC (Group Transfer Concentration)
Authors: Yu, C., W.A. Jester, and A.R. Jarrett
Institution of Model Development: Argonne National Laboratory
Argonne, IL 60439
Code Custodian: Charles Yu
Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439
Abstract:
GTC is a general purpose finite difference solute transport model developed to simulate solute movement
in heterogeneous porous media. It splits up the modeled area in zones of constant properties, including
dispersion coefficient, retardation factor, and degradation rate. Mass transfer between the solid phase and
the liquid phase is proportional to the concentration gradient. The GTC model can be used for both
saturated and unsaturated conditions. It covers the conventional advection-dispersion model, the mobile-
immobile pore model, the nonequilibrium adsorption-desorption model and the jointed porous rock model.
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Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications)
Documentation includes: model theory
Availability: restricted public domain
References:
Yu, C., W.A. Jester, and A.R. Jarrett. 1985. A General Solute Transport Model and its Applications
in Contaminant Migration Analysis. CONF-850893--1, Argonne National Lab., Argonne, Illinois.
IGWMC Key: 6710 Model Name: CMIS (Chemical Movement in Soil)
Authors: Nofziger, D.L, and A.G. Hornsby
Institution of Model Development: Florida Coop. Extension Service
University of Florida, Gainesville, Florida
Code Custodian: Inst. of Food and Agric. Sciences, IFAS
University of Florida, Building 664, Gainesville, FL 32611
Abstract:
CMIS is a management/educational computer program that provides qualitative predictions of pesticide fate
as function of key soil, chemical, and climatic variables. Model assumptions limit it to nonpolar pesticides
(and other xenobiotics) moving in sandy soils. Linear adsorption/desorption isotherms are used to describe
chemical affinity to the soil matrix.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications), demonstration/education
Documentation includes: model theory, user's instructions, example problems, verification/validation
Verification/validation: verification (analyt.solutions), laboratory data sets
Peer (independent) review: concepts, theory (math)
Availability: proprietary, purchase
Remarks:
An updated and expanded version of CMIS by the same author is CMLS (Chemical Movement in
Layered Soils); Nofziger and Hornsby, 1988 (see references); also IGWMC Key #6711.
References:
Nofziger, D.L, and A.G. Hornsby. 1985. Chemical Movement in Soils: IBM PC User's Guide.
Circular 654, Florida Coop. Ext. Serv., Univ. of Florida, Gainesville, Florida.
O'Connor, G.A., and F. Khorsandi. 1986. Predicting Chemical Movement in Soils. WRRIRept. M17,
New Mexico Water Resources Research Inst., New Mexico State Univ., Las Cruces, New Mexico.
Nofziger, D.L, and A.G. Hornsby. 1988. Chemical Movement in Layered Soils: User's Manual.
Circular 780, Inst. of Food and Agric. Sciences, Univ. of Florida, Gainesville, Florida. (Also:
Computer Software Series CCS-30, Agric. Exp. Station, Div. of Agric., Oklahoma State Univ.,
Stillwater, Oklahoma).
Nofziger, D.L, R.S. Mansell, L.B. Baldwin, and M.F. Laurent. 1983. Pesticides and their Behavior
in Soil and Water. Report SL-40 (revised), Florida Cooperative Extension Service, University of
Florida, Gainesville, Florida.
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IGWMC Key: 6711 Model Name: CMLS (Chemical Movement in Layered Soils)
Authors: Nofziger, D.L (1), and A.G. Hornsby (2)
Institution of Model Development: 1) Oklahoma State University, Stillwater, Oklahoma
2) University of Florida, Gainesville Florida
Code Custodian: Inst. of Food and Agric. Sciences, IFAS
University of Florida, Building 664, Gainesville, FL 32611
Abstract:
CMLS is an interactive microcomputer model to be used as management tool and a decision aid in the
application of organic chemicals to soils. The model estimates the location of the peak concentration of
non-polar organic chemicals as they move through a soil in response to the downward movement of water.
The model also estimates the relative amount of each chemical still in the soil at any time. The model can
deal with soils with up to 20 layers or horizons, each having its own partition coefficient and degradation
half-life of the chemical of interest.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications), demonstration/education
Documentation includes: model theory, user's instructions, example problems, verification/validation
Verification/validation: verification (analyt.solutions)
Peer (independent) review: concepts, theory (math)
Availability: proprietary, purchase
Remarks:
This software is based on a model published by Nofziger and Hornsby (1986; see references). That
model is an expansion of the model presented by Rao et Al (1976; see references). It is also an
expansion of the CMIS (Chemical Movement in Soils) model of Nofziger and Hornsby (1985; see
IGWMC Key # 6710).
References:
Nofziger, D.L, and A.G. Hornsby. 1988. Chemical Movement in Layered Soils: User's Manual.
Circular 780, Inst. of Food and Agric. Sciences, Univ. of Florida, Gainesville, Florida. (Also:
Computer Software Series CCS-30, Agric. Exp. Station, Div. of Agric., Oklahoma State Univ.,
Stillwater, Oklahoma).
Nofziger, D.L, and A.G. Hornsby. 1986. A Microcomputer-Based Management Tool for Chemical
Movement in Soil. Applied Agric. Research, Vol. 1, pp. 50-56.
Rao, P.S.C., J.M. Davidson, and LC. Hammond. 1976. Estimation of Nonreactive and Reactive
Solute Front Locations in Soils. EPA-600/9-075-015, Office of Research and Developm, U.S. Env.
Protection Agency, Washington, D.C.
IGWMC Key: 3541 Model Name: GLEAMS
Authors: Leonard, R.A., W.G. Knisel, and F.M. Davis
Institution of Model Development: U.S.D.A. Agricultural Research Station
Southeast Watershed Experimental Station
Tifton, Georgia
Code Custodian: R.A. Leonard, W.G. Knisel or F.M. Davis
USDA-ARS, P.O. Box 946, Tifton, GA 31793
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Abstract:
GLEAMS (Groundwater Loading Effects on Agricultural Management Systems) was developed as an
extension of an earlier USDA model, CREAMS. Both models simulate soil water balance and surface
transport of sediments and chemicals from agricultural field management units. GLEAMS, in addition,
simulates chemical transport in and through the plant root zone. Several other features were added such
as irrlgation/chemigation options, pesticide metabolite tracking, and software to facilitate model
implementation and output data analysis. Input requirements for the model include daily rainfall volumes,
crop and management parameters; soil and physical parameters; pesticide property data such as solubility,
and expected half-life in soil and/or foliage.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications), demonstration/education
Documentation includes: model theory, user's instructions, example problems, program structure
and development, code listing, verification/validation
Verification/validation: laboratory data sets, field datasets (validation)
Availability: public domain
Remarks:
As of mid 1990, since its release in late 1986, over 500 copies of GLEAMS have been provided to
users worldwide (Leonard et al. 1990). Since its first release it has been constantly updated and
expanded.
The predecessor to GLEAMS, CREAMS, is annotated as IGWMC key # 3540.
References:
Leonard, R.A., W.G. Knisel, and D.A. Still. 1987. GLEAMS: Groundwater Loading Effects of
Agricultural Management Systems. Transactions of ASEA, Vol. 30(5), pp. 1403-1418.
Knisel, W.G. 1990. CREAMS/GLEAMS: A Development Overview. In: Proceed, of the
CREAMS/GLEAMS Symposium, Univ. of Georgia, Athens, Georgia.
Leonard, R.A., W.G. Knisel, P.M. Davis, and A.W. Johnson. 1988. Modeling Pesticide Metabolite
Transport with GLEAMS. In: Proceed. ASCE, Irrigation and Drainage Specialty Conference, Lincoln,
Nebraska, July 11-14, pp. 255-262. Am. Soc. of Civil Eng., Boston, Mass.
Leonard, R.A., W.G. Knisel, P.M. Davis, and A.W. Johnson. 1990. Validating GLEAMS with Field
Data for Fenamiphos and its Metabolites. Journ. Irrigation and Drainage Eng., Vol. 116, pp. 24-35.
Leonard, R.A., W.G. Knisel, and P.M. Davis. 1990. The GLEAMS Model - A Tool for Evaluating
Agrichemical Ground-Water Loading as Affected by Chemistry, Soils, Climate and Management.
In: E.B. Janes and W.R. Hotchkiss (eds.), Transferring Models to Users, Denver, Colorado,
November 4-8, 1990, pp. 187-197. Am. Water Resources Assoc., Bethesda, Maryland.
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IGWMC Key: 6712 Model Name: CHEMFLO
Authors: Nofziger, D.L, K. Rajender, S.K. Nayudu, and P-Y. Su.
Institution of Model Development: Oklahoma State University
Dept. of Agronomy, Stillwater, Oklahoma
Code Custodian: J.R. Williams
R.S. Kerr Environm. Res. Lab., U.S. EPA, Ada, Oklahoma 74820
Abstract:
CHEMFLO is an interactive program for simulating water and chemical movement in unsaturated soils.
Water movement is modeled using the Richards equation. Chemical transport is modeled by means of the
convection-dispersion equation. These equations are solved numerically for one-dimensional flow and
transport using finite differences. Results of the flow model can be displayed in the form of graphs of water
content, matric potential, driving force, conductivity, and flux density of water versus distance or time.
Graphs of concentration, and flux density of chemical as function of distance or time can also be displayed.
CHEMFLO is an expansion and update of the water movement model WATERFLO by Nofziger (1985).
Model developed for: general use (e.g. in field applications), demonstration/education
Documentation includes: model theory, user's instructions, example problems
Peer (independent) review: concepts, theory (math), documentation
Availability: public domain
Remarks:
CHEMFLO is an extension and update of WATERFLO by Nofziger (1985; see IGWMC key # 6630).
Soil and chemical parameters required by the model include: soil bulk density, water-soil partition
coefficient, diffusion coefficient of chemical in water, dispersivity, first-order degradation rates for
contaminant in the water and the solid phases, and a zero order rate constant for the liquid. Other
parameters required for solving the Richards equation are the function relationships for soil-water
retention and unsaturated hydraulic conductivity.
References:
Nofziger, D.L, K. Rajender, S.K. Nayudu, and P-Y Su. 1989. CHEMFLO: One-Dimensional Water
and Chemical Movement in Unsaturated Soils. EPA/600/8-89/076, U.S. Environm. Protection
Agency, R.S. Kerr Environm. Research Lab., Ada, Oklahoma.
IGWMC Key: 6390 Model Name: MOUSE
Authors: Pacenka, S., and T. Steenhuis
Institution of Model Development: Cornell University, Agricultural Eng. Dept., Ithaca, New York
Code Custodian: T. Steenhuis, Cornell University, Agric. Eng. Dept., Ithaca, New York
Abstract:
MOUSE (Method Of Underground Solute Evaluation) is developed for classroom and Cooperative Extension
Service educational purposes. The model tracks soluble chemical movement in both the saturated and the
unsaturated zone by coupling 1D vertical flow and transport in three-layer soils with 2D cross-sectional flow
and transport in an anisotropic, heterogeneous aquifer. Surface runoff is calculated using the USDA Soil
Conservation Service curve number equation. Active evapotranspiration occurs in the top layer of the soil.
The finite difference model includes first-order degradation, dispersion, diffusion and convective mass
movement. Furthermore, the model can handle linear equilibrium adsorption/desorption isotherms.
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Model developed for: general use (e.g. in field applications), demonstration/education
Documentation includes: model theory, user's instructions, example problems, verification/validation
Verification/validation: verification (analyt.solutions)
Availability: public domain
References:
Pacenka, S, and T. Steenhuis. 1984. User's Guide for the MOUSE Computer Program. Agricultural
Engineering Dept., Cornell University, Ithaca, New York.
IGWMC Key: 3411 Model Name: LEACHM
Authors: Wagenet, R.J., and J.L Hutson
Institution of Model Development: Cornell University, Ithaca, New York
Code Custodian: J.L. Hutson
Dept. of Soil, Crop and Atmospheric Sciences, Cornell University, Ithaca, NY 14853
Abstract:
LEACHM (Leaching Estimation And CHemistry Model) refers to five versions of a simulation model which
describes the water regime and the transport and fate of chemicals in the shallow unsaturated zone. The
Richard's equation and the convective-dispersive transport equations are solved for multilayered soil profiles
under transient flow conditions using finite differences. The models handle plant uptake of water and
solutes, and multiple rainfall and surface evaporation cycles. The models are organized on a modular basis
with separate routines for each of the simulated processes.
LEACHN describes nitrogen transport and transformation. It includes the transport of urea, ammonium and
nitrate accounting for (linear) sorption, sources and sinks. The model includes diffusion in the gas phase
if the chemical is volatile. Nitrogen transformations include three mineralization reactions, nitrification, and
denitrification. Plant uptake of nitrogen can be simulated using Watts and Hanks approach or the
Nye/Warncke approach.
LEACHP simulates movement and fate of pesticides and other miscible organic compounds accounting for
linear sorption on the solid phase and diffusion in the gas phase. It can simulate the fate of many chemicals
simultaneously. The various species may be grouped in degradation or transformation pathways. Pesticides
can be applied in wet or dry form to the soil surface. The program allows for oxidation and hydrolysis
reactions.
LEACHC describes the movement of the major inorganic cations an anions in soil. It calculates chemical
equilibrium between solution, exchange and precipitated phases at user-specified intervals. The sink term
in the transport equation is used to represent plant uptake. Because of competiveness of the multi-cation
exchange process special subroutines are included for cation exchange, precipitation-dissolution, and
atmospheric exchange.
LEACHB describes microbial population dynamics in the presence of a single growth-supporting substrate.
Microbial growth and utilization are described by Monod-type equations. Equations for predator-prey
systems in flowing water are included. The model has various options to introduce substrate and allows
for an indigenous supply of substrate.
LEACHW describes the water regime only. A heat flow model producing soil temperature profiles is included
in LEACHN and LEACHP.
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Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications)
Documentation includes: model theory, user's instructions, example problems, verification/validation
Verification/validation: verification (analyt.solutions)
Peer (independent) review: concepts, theory (math)
Availability: public domain
References:
Wagenet, R.J., and J.L. Hutson. 1986. Predicting the Fate of Nonvolatile Pesticides in the
Unsaturated Zone. Journ. of Environmental Quality, Vol. 15, pp. 315-322.
Hutson, J.L, and R.J. Wagenet. 1992. LEACHM Leaching Estimation And Chemistry Model; A
Process-Based Model of Water and Solute Movement, Transformations, Plant Uptake and Chemical
Reactions in the Unsaturated Zone, Version 3. Research Series No. 92-3, Dept. of Soil, Crop and
Atmosph. Sciences, Cornell Univ., Ithaca, New York.
IGWMC Key: 4140 Model Name: MLSOIL/DFSOIL
Authors: Sjoreen, A.L, D.C. Kocher, G.G. Killough, and C.W. Miller.
Institution of Model Development: Oak Ridge National Laboratory, Oak Ridge, Tennessee
Code Custodian: A.L Sjoreen
Oak Ridge National Laboratory, Health and Safety Research Division
Oak Ridge, Tennessee 37831
Abstract:
MLSOIL (Multi-Layer SOIL model) calculates an effective ground surface concentration to be used in
computations of external doses. The program implements a five compartment linear-transfer model to
calculate the concentrations of radionuclides in the soil following deposition on the ground surface from the
atmosphere. The model considers leaching through the soil as well as radioactive decay and buildup.
DFSOIL calculates the dose in air per unit concentration at 1 m above the ground from each of the five soil
layers used in MLSOIL and the dose per unit concentration from an infinite plane source. MLSOIL and
DFSOIL are part of the Computerized Radiological Risk Investigation System (CRRIS).
Model developed for: general use (e.g. in field applications)
Documentation includes: model theory, user's instructions, example problems, program structure
and development, code listing, verification/validation
Verification/validation: verification (analyt.solutions)
Peer (independent) review: concepts, theory (math), documentation
Availability: public domain
References:
Sjoreen, A.L., D.C. Kocher, G.G. Killough, and C.W. Miller. 1984. MLSOIL and DFSOIL - Computer
Code to Estimate Effective Ground Surface Concentrations for Dose Computations. ORNL-5974,
Oak Ridge National Lab., Oak Ridge, Tennessee.
IGWMC Key: 4931 Model Name: TARGET-2DU
Authors: Moreno, J.L, M.I. Asgian, S.D. Lympany, and P-J. Pralong.
Institution of Model Development: Dames & Moore, Denver, Colorado
Code Custodian: Moreno, J.L.
Dames & Moore, 1125 17th Str, #1200, Denver, Colorado 80202
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Abstract:
TARGET-2DU is one of five models of the TARGET series (Transient Analyzer of Reacting Groundwater and
Effluent Transport). It simulates two-dimensional, variably saturated, density coupled, transient groundwater
flow and solute transport using a hybrid finite difference method. The transport is based on the solution
of the advective-dispersive transport equation for a single non-conservative contaminant with linear
equilibrium adsorption (retardation). The solution method used is based on an iterative alternating direction
implicit method.
Model developed for: general use (e.g. in field applications)
Documentation includes: model theory, user's instructions, example problems, program structure
and development, verification/validation
Verification/validation: verification (analyt.solutions)
Availability: proprietary, license
References:
Dames & Moore. 1985. Physical and Mathematical Background of Two-Dimensional and
Three-Dimensional Variably Saturated, Density Coupled Models. Denver, Colorado.
Dames & Moore. 1985. User's Guide to TARGET 2DU, Version 4.0. Denver, Colorado.
IGWMC Key: 4934 Model Name: TARGET-SOU
Authors: Moreno, J.L, M.I. Asgian, S.D. Lympany, and P-J. Pralong
Institution of Model Development: Dames & Moore, Denver, Colorado
Code Custodian: J.L Moreno
Dames & Moore, 1125 17th. Str., #1200, Denver, Colorado 80202
Abstract:
TARGET-SOU is one of five models of the TARGET series (Transient Analyzer of Reacting Groundwater and
Effluent Transport). It simulates three-dimensional, variably-saturated, density-coupled, transient groundwater
flow and solute transport using a hybrid finite difference method. The transport is based on the solution
of the advective-dispersive transport equation for a single non-conservative contaminant with linear
equilibrium adsorption (retardation). The solution method used is based on an iterative alternating direction
implicit method.
Model developed for: general use (e.g. in field applications)
Documentation includes: model theory, user's instructions, example problems, program structure
and development, verification/validation
Verification/validation: verification (analyt.solutions)
Availability: proprietary, license
References:
Dames & Moore. 1985. Physical and Mathematical Background of Two-Dimensional and
Three-Dimensional Variably Saturated, Density Coupled Models. Denver, Colorado.
Dames & Moore. 1985. User's Guide to TARGET-SOU, Version 4.0. Denver, Colorado.
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IGWMC Key: 4693 Model Name: VADOFT
Authors: Huyakorn, P.S., T.D. Wadsworth, H.O. White Jr., and J.E. Buckley
Institution of Model Development: Hydrogeologic, Inc., Herndon, Virginia
Code Custodian: Jan Kool
Hydrogeologic, Inc., 1165 Herndon Parkway, #900, Herndon, VA 22070
Abstract:
VADOFT is a one-dimensional finite element code that solves the Richard's equation for flows in the
unsaturated zone. The user may make use of constitutive relationships between pressure, water content,
and hydraulic conductivity to solve the flow equations. VADOFT also simulates the fate and transport of two
parent and two daughter products.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications)
Availability: public domain
Remarks:
PRZM, VADOFT and SAFTMOD are part of RUSTIC. RUSTIC (IGWMC Key # 4721) links these
models in order to predict the fate and transport of chemicals to drinking water wells. The codes
are linked together with the aid of a flexible execution supervisor (software user interface) that allows
the user to build models that fit site-specific situations.
References:
Huyakorn, P.S., T.D. Wadsworth, H.O. White, Jr., and J.E. Buckley. 1987. VADOFT' Version 3.2,
Project Report for USEPA, Environm. Research Lab., Athens, Georgia. Hydrogeologic, Inc.,
Herndon, Virg.
See also references of RUSTIC (IGWMC # 4721).
IGWMC Key: 5186 Model Name: NITRO
Authors: Kaluarachchi, J.J., and J.C. Parker
Institution of Model Development: Environmental Systems & Technologies, Inc., Blacksburg, Virginia
Code Custodian: J.C. Parker
Environmental Systems & Technologies, Inc.
P.O. Box 10457, Blacksburg, VA 24062-0457
Abstract:
NITRO is a 2-dimensional vertical section or radially symmetric finite element program for simulation of
steady-state and transient uncoupled flow and transport in the unsaturated zone. The nonlinearity is handled
by Picard iteration. Soil hydraulic properties are described by the Brooks-Corey or van Genuchten model
with hysteresis. The model handles transport of up to two species with linear or Freundlich equilibrium
adsorption and zero and first order transformations. It facilitates atmospheric and seepage boundaries as
well as first-type and second-type (flux) boundary conditions.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications)
Documentation includes: user's instructions, example problems
Availability: proprietary, license
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IGWMC Key: 5220 Model Name: VSAFT2 (Variably SAturated Flow and Transport in 2 dimensions)
Authors: Yeh, T-C.J.
Institution of Model Development: The University of Arizona, Dept. of Hydrology and Water Resources
Tuscon, Arizona
Code Custodian: T-C.J. Yeh
Dept. of Hydrology and Water Resources
University of Arizona, College of Engineering and Mines
Building 11, Tuscon, AZ 85721
Abstract:
VSAFT2 is a program for simulating two-dimensional steady or transient, variably saturated flow and
convective-dispersive transport of a conservative solute, using a finite element method with the
Newton-Raphson or Picard iteration scheme. For the linear equation solution a preconditioned conjugate
gradient method is used. Solute transport is handled by an upstream weighing scheme. The model uses
rectangular and/or triangular finite elements and a banded matrix solver. The two-dimensional flow can be
either in a horizontal or in a vertical plane. Furthermore, the model can handle radial symmetric simulations.
The code contains a restart feature for changing boundary conditions.
Model developed for: research (e.g. hypothesis/theory testing)
Documentation includes: model theory, user's instructions, example problems, program structure
and development, code listing, verification/validation
Verification/validation: verification (analyt.solutions), code intercomparison
Availability: public domain
Remarks:
Evapotranspiration is simulated in VSAFT2 by a user specified root zone consisting of one or more
plant species. User supplied information on the root zone includes wilting pressure, maximum
transpiration rate, root effectiveness function, and root zone geometric data. Evaporation \
Infiltration is simulated through user defined maximum evaporation or infiltration rates, minimum soil
surface pressure head, and soil surface geometric data. Analytical functions must be used for
relative hydraulic conductivity relationships and moisture characteristic curve functions. The user
is given the choice of the van Genuchten model, exponential model, Gardener-Russo model, or a
user specified function for which a subroutine must be written.
Documentation includes test problems where results from VSAFT2 are compared to UNSAT2,
FEMWATER/FEMWASTE, VAM2D, and VADOFT.
References:
Yeh, T-C.J., and R. Srivastava. 1990. VSAFT2: Variably Saturated Flow and Transport in
2-Dimensions; a Finite Element Simulation. Technical Report No. HWR 90-010, Dept. of Hydrology
& Water Resources, The University of Arizona, Tuscon, Arizona.
IGWMC Key: 5221 Model Name: VSAFT3 (Variably SAturated Flow and Transport in 3 dimensions)
Authors: Srivastava, R. and T-C.J. Yeh
Institution of Model Development: The University of Arizona, Dept. of Hydrology and Water Resources
Tuscon, Arizona
Code Custodian: T.C.J. Yeh
Dept. of Hydrology and Water Resources, Univ. of Arizona
Building 11, Tuscon, AZ 85721
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Abstract:
VSAFT3 is a three-dimensional finite element model for simulation of transient flow and convective-dispersive
transport in variably saturated porous media. The resulting flow matrix equations are solved using a Picard
iteration scheme and a continuous velocity field is obtained by separate application of the Galerkin technique
to the flux equation. A two-site adsorption-desorption model with first-order loss term is used for the reactive
solute. The advective part of the transport equation is solved with one-step backwards particle tracking
(MMOC), while the dispersive part is solved using the regular Galerkin finite element technique. The
resulting matrix equations are solved with a PGJ method. The code contains a restart feature for changing
boundary conditions.
Model developed for: research (e.g. hypothesis/theory testing)
Documentation includes: model theory, user's instructions, example problems, program structure
and development, code listing, verification/validation
Verification/validation: verification (analyt.solutions), code intercomparison
Availability: public domain
References:
Srivastava, R., and T-C.J. Yen. 1992. A Three-Dimensional Numerical Model for Water Flow and
Transport of Chemically Reactive Solute Through Porous Media under Variably Saturated
Conditions. Submitted to Adv. in Water Resources.
IGWMC Key: 4721 Model Name: RUSTIC
Authors: Dean, J.D., P.S. Huyakorn, A.S. Donigan, Jr., K.A. Voos, R.W. Schanz, Y.J. Meeks, and R.F.
Carsel
Institution of Model Development: Woodward-Clyde Consultants, Oakland, California
Code Custodian: R.F. Carsel
U.S. Environmental Protection Agency
Environmental Research Laboratory, Athens, GA 30613
Abstract:
RUSTIC is a coupled root 2one (PR2M), unsaturated zone (VADOFT), and saturated zone (SAFTMOD)
modeling package. RUSTIC links these models in order to predict the fate and transport of chemicals to
drinking water wells. The codes are linked together with the aid of a flexible execution supervisor (software
interface) that allows the user to build models that fit site-specific situations. For exposure assessments,
the code is equipped with a Monte Carlo pre- and post-processor.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications)
Availability: public domain
Remarks:
PRZM (MARS Key # 4720) is a one-dimensional finite difference model which accounts for pesticide
fate and transport in the crop root zone. The version included in RUSTIC incorporates several
features added to the original code, such as soil temperature effects, volatilization and vapor phase
transport in soils, irrigation simulation and a method of characteristics algorithm to eliminate
numerical dispersion. This PRZM version is capable of simulating fate and transport of the parent
and up to two daughter species.
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VADOFT (MARS Key # 4693) is a one-dimensional finite element code that solves the Richard's
equation for flows in the unsaturated zone. The user may make use of constitutive relationships
between pressure, water content, and hydraulic conductivity to solve the flow equations. VADOFT
also simulates the fate and transport of two parent and two daughter products.
SAFTMOD (MARS Key # 4694) is a two-dimensional finite element model that simulates saturated
solute flow and transport in either X-Y or X-Z configuration.
References:
Dean, J.D., P.S. Huyakorn, A.S. Donigan, Jr., K.A. Voos, R.W. Schanz, Y.J. Meeks, and R.F. Carsel.
1989. Risk of Unsaturated /Saturated Transport and Transformation of Chemical Concentrations
(RUSTIC); Volume 1: Theory and Code Verification. EPA/600/3-89/048a, U.S. EPA, ORD/ERL,
Athens, Georgia.
Dean, J.D., P.S. Huyakorn, A.S. Donigan, Jr., K.A. Voos, R.W. Schanz, Y.J. Meeks, and R.F. Carsel.
1989. Risk of Unsaturated /Saturated Transport and Transformation of Chemical Concentrations
(RUSTIC); Volume 2: User's Guide. EPA/600/3-89/048b, U.S. EPA, ORD/ERL, Athens, Georgia.
IGWMC Key: 5630 Model Name: MULTIMED
Authors: Salhotra, A.M., P. Mineart, S. Sharp-Hansen, and T. Allison
Institution of Model Development: U.S. EPA, Environmental Res. Lab., Athens, Georgia
Code Custodian: Center for Exposure Assessment Modeling
U.S. Environmental Protection Agency
Environmental Research Lab., College Station Road,
Athens, GA30613
Abstract:
MULTIMED is a multimedia transport model that simulates the movement of contaminants leaching from a
waste disposal facility. The model includes two options or simulating leachate flux. Either the infiltration rate
to the unsaturated or saturated zone can be specified directly or a landfill module can be used to estimate
the infiltration rate. The landfill module is one-dimensional and steady-state, and simulates the effect of
precipitation, runoff, infiltration, evapotranspiration, barrier layers (which can include flexible membrane
liners), and lateral drainage. A steady-state, one-dimensional, semi-analytical module simulates flow in the
unsaturated zone. The output from this module, water saturation as function of depth, is used as input to
the unsaturated transport module. The unsaturated transport module simulates transient, one-dimensional
(vertical) transport and includes the effects of longitudinal dispersion, linear adsorption, and first-order decay.
Output from this module -i.e. steady-state or time-varying concentrations at the water table- is used to
couple the unsaturated zone transport module with a steady-state or transient, semi-analytical saturated zone
transport module. The saturated zone transport model of MULTIMED includes one-dimensional uniform flow,
three-dimensional dispersion, linear adsorption (retardation), first-order decay, and dilution due to direct
infiltration into the ground water plume. Contamination of a surface stream due to the complete interception
of a steady-state saturated zone plume is simulated by the surface water module. Finally, the air emissions
and the atmosphere dispersion modules simulate the movement of chemicals into the atmosphere. The
module includes option for Monte Carlo simulations.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications)
Availability: public domain
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References:
Salhotra, A.M., P. Mineart, S. Sharp-Hansen, and T. Allison. 1990. Multimedia Exposure
Assessment Model (MULTIMED) for Evaluating the Land Disposal of Wastes - Model Theory.
Report Contract # 68-03-3513 and 68-03-6304, U.S. EPA, Env. Res. Lab., Athens, Georgia.
Sharp-Hansen, S., C. Traverse, P. Hummel, and T. Allison. 1990. A Subtitle D Landfill Application
Manual for the Multimedia Exposure Assessment Model (MULTIMED). Report Contract # 68-03-
3513, U.S. EPA, Env. Res. Lab., Athens, Georgia.
IGWMC Key: 5310 Model Name: PRZMAL
Authors: Wagner, J., and C. Ruiz-Calzada
Institution of Model Development: Oklahoma State University
School of Chemical Engineering, Stillwater, Oklahoma
Code Custodian: J. Wagner
Oklahoma State University, School of Chemical Engineering, Stillwater, OK 74074
Abstract:
PRZMAL is an aquifer linkage model for US EPA's Pesticide Root Zone Model (PRZM). It connects PRZM
with the analytical three-dimensional transport model PLUME 3D developed at Oklahoma State University.
This linkage allows the user to predict contaminant movement from the point of application, in a continuous
manner, into and within the aquifer.
Model developed for: general use (e.g. in field applications)
Documentation includes: model theory, user's instructions
Availability: public domain
Remarks:
PRZM (MARS Key # 4720) is a one-dimensional finite difference model which accounts for pesticide
fate and transport in the crop root zone. It includes soil temperature effects, volatilization and vapor
phase transport in soils, irrigation simulation and a method of characteristics algorithm to eliminate
numerical dispersion. PRZM is capable of simulating fate and transport of the parent and up to two
daughter species.
Wagner and Ruiz designed an aquifer linkage model PRZMAL to connect PRZM with the analytical
three-dimensional model PLUME 3D.
References:
Wagner, J., and C. Ruiz-Calzada. 1986. User's Manual for PRZM-Aqurfer (PRZMAL). Oklahoma
State University, School of Chemical Engineering, Stillwater, Oklahoma.
IGWMC Key: 5681 Model Name: VIP (Vadose zone Interactive Processes model)
Authors: Stevens, O.K., W.J. Grenney, and Z. Van
Institution of Model Development: Civil and Environm. Eng., Utah State Univ., Logan, Utah
Code Custodian: D.K. Stevens
Civil and Environm. Eng. Dept., Utah State Univ., UMC 4110, Logan, Utah 84321
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Abstract:
VIP is an one-dimensional finite-difference solute transport and fate model for simulating the behavior of
organic (oily) compounds in the vadose zone as part of a land treatment system. The model uses advection
and dispersion in the water and air phases as the dominant transport mechanism for contaminant and
oxygen. Monthly values for recharge rate and soil moisture conditions are used to calculate an effective
water velocity. The model includes first-order degradation of a contaminant in water, air and soil, and of
oxygen. It uses an implicit technique to calculate the degradation of the contaminant in the oil phase as
well as the oil phase itself, and related oxygen changes, (see also remarks).
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications)
Documentation includes: model theory, user's instructions, example problems, program structure
and development, and verification/validation
Verification/validation: laboratory data sets, field datasets (validation)
Peer (independent) review: concepts, theory
Availability: public domain
Remarks:
VIP uses partition coefficients and rate constants to calculate contaminant concentration in each
medium. The model has various output options including echo of input data, (graphic) profile of
initial condition (constituent concentration in water, oil, air, and soil phases), and the initial fractions
as well as initial oxygen concentration. Other output options include (graphic) depth-concentration
profiles and data versus time tables. Input preparation facilitates exchange of Lotus 123 and
word processed ASCII files.
This software is available from: Center for Subsurface Modeling Support (CSMOS), R.S. Kerr
Environmental Research Laboratory, U.S. Environmental Protection Agency, P.O. Box 1198, Ada,
OK 74820, Phone: 405/332-8800.
References:
Stevens, O.K. W.J. Grenney, and Z. Van. 1991. A Model for the Evaluation of Hazardous
Substances in the Soil. Version 3.0. Civil and Environm. Eng. Dept., Utah State Univ., Logan, Utah.
Grenney, W.J., G.L Caupp, R.C. Sims, and T.E. Short. 1987. A Mathematical Model for the fate
of Hazardous Substances in Soil: Model Description and Experimental Results. Haz. Waste & Haz.
Mat., Vol. $(3), pp. 223-239
IGWMC Key: 5850 Model Name: RZWQM (Root Zone Water Quality Model)
Authors: DeCoursey, D.G., K.W. Rojas, and LR. Ahuja
Institution of Model Development: USDA-ARS, Fort Collins, Colorado
Code Custodian: Lajpat R. Ahuja
Agricultural Research Service, U.S. Dept. of Agric., Hydro-Ecosystems Research
Group, P.O. Box E, Fort Collins, CO 80522
Abstract:
RZWQM is a physically based model simulating the movement of water, nutrients, and pesticides over and
through the root zone at a representative point in a field. The physical processes included are soil matrix
infiltration, macropore flow, surface runoff, heat flow, potential evaporation, and transpiration, soil-water
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redistribution and chemical transport. Root water uptake, actual evaporation and transpiration, are
calculated in the crop growth section in conjunction with water redistribution and plant growth. Soil
chemical processes include bicarbonate buffering, dissolution and precipitation of calcium carbonate,
gypsum, and aluminum hydroxide, ion exchange involving bases and aluminum, and solution chemistry of
aluminum hydroxide, (see also remarks).
Model developed for: general use (e.g. in field applications), demonstration/education
Documentation includes: user's instructions
Verification/validation: under development (as of 7/'92)
Peer (independent) review: under development
Availability: public domain; test version only
Remarks:
RZWQM also includes various nutrient processes such as decomposition of organic matter,
mineralization, immobilization and demineralization of appropriate nitrogen and phosphorus species,
and adsorption/desorption of both species. Pesticide processes the model can handle include
computation of the amount of pesticides reaching the soil surface, and the amounts absorbed and
moving through each soil layer. Dissipation via volatilization, photolysis, hydrolysis, biodegradation,
oxidation, and complexation are simulated. These processes may be lumped in a single process.
Other pesticide related processes simulated in RZWQM are dissipation by formulation of metabolites
(tracked throughout their life time). Either equilibrium isotherms or kinetic adsorption/desorption
processes may be simulated. The model allows to include certain management practices such as
effects of tillage practices on chemical distribution, soil density, and macro- and microporosity;
fertilizer and pesticide applications; planting densities; and irrigation and drainage practices.
References:
Hebson, C.S., and D.G. DeCoursey. 1987. A Model for Assessing Management Impact on
Root-Zone Water Quality. In: Proceed. Am. Chem. Soc. 193rd. Nat. Meeting, Agro Chemicals Div.,
Denver, Colorado, April 5-10, 1987.
Hebson, C.S., and D.G. DeCoursey. 1987. A Model for Ranking Land-Use Management Strategies
to Minimize Unsaturated Zone Contamination. In: Proceed. ASCE Eng. Hydrology Symposium,
Williamsburg, Virginia, August 3-5, 1987.
IGWMC Key : 6221 Model Name: SWMS-2D
Authors: Simunek, J., T. Vogel and M.Th. van Genuchten
Institution of Model Development: U.S. Salinity Laboratory, Agricultural Research Service
Dept. of Agriculture, Riverside, Calif.
Code Custodian: M.Th. van Genuchten
Institution: U.S. Salinity Laboratory, Agricultural Research Service
U.S. Dept. of Agriculture, 4500 Glenwood Drive, Riverside, CA 92501
Abstract:
The program 'SWMS_2D' is a numerical model for simulating water and solute movement in two-dimensional
variably saturated media. The program numerically solves the Richards' equation for saturated-unsaturated
water flow and the advection-dispersion equation for solute transport. The flow equation incorporates a sink
term to account for water uptake by plant roots. The transport equation includes provisions for linear
equilibrium adsorption, zero-order production and first-order degradation. The program may be used to
analyze water and solute movement in unsaturated, partially saturated, or fully saturated porous media.
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SWMS_2D can handle flow regions delineated by irregular boundaries. The flow region itself 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, or in a three-dimensional region exhibiting radial symmetry about
the vertical axis. The water flow part of the model can deal with (constant or varying) prescribed head and
flux boundaries, as well as boundaries controlled by atmospheric conditions. Soil surface boundary
conditions may change from prescribed flux to prescribed head type conditions (and vice-versa). The code
can also handle a seepage face boundary through which water leaves the saturated part of the flow domain.
For solute transport the code supports both (constant and varying) prescribed concentration (Dirichlet or
first-type) and concentration flux (Cauchy or third-type) boundaries. The dispersion tensor includes a term
reflecting the effects of molecular diffusion and tortuosity.
The unsaturated soil hydraulic properties are described by a set of closed-form equations resembling the
1980 van Genuchten equations. Modifications were made to improve the description of hydraulic properties
near saturation. SWMS_2D implements a scaling procedure to approximate the hydraulic variability in a
given area by means of a set of linear scaling transformations which relate the individual soil hydraulic
characteristics to reference characteristics.
The governing equations are solved using a Galerkin type linear finite element method applied to a network
of triangular elements. Integration in time is achieved using an implicit (backwards) finite difference scheme
for both saturated and unsaturated conditions. The resulting equations are solved in an iterative fashion,
by linearization and subsequent Gaussian elimination. Additional measures are taken to improve solution
efficiency in transient problems, including automatic time step adjustment and checking if the Courant and
Peclet numbers do not exceed a preset level. The water content term is evaluated using the
mass-conservative method proposed by Celia et al. (1990). To minimize numerical oscillations upstream
weighing is included as an option for solving the transport equation.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications), demonstration/education
Documentation includes: model theory, user's instructions, example problems, program structure
and development, code listing, and verification/validation
Verification/validation: verification (analyt.solutions), laboratory data sets, code intercompariosn
Peer (independent) review: concepts, theory (math), documentation
References
Simunek, J., T. Vogel and M.Th. van Genuchten. 1992. The SWMS_2D Code for Simulating Water
Row and Solute Transport in Two-Dimensional Variably Saturated Media; Version 1.1. Research
Report 126, U.S. Salinity Laboratory, USDA/ARS, Riverside, California.
IGWMC Key : 6229 Model Name: HYDRUS/WORM
Authors: Kool, J.B., M.Th. van Genuchten
Institution of Model Development: U.S. Salinity Laboratory, Agricultural Research Service
Dept. of Agriculture, Riverside, Calif.
Code Custodian: M.Th. van Genuchten
Institution: U.S. Salinity Laboratory, Agricultural Research Service
U.S. Dept. of Agriculture, 4500 Glenwood Drive, Riverside, CA 92501
Abstract:
HYDRUS is a Galerkin linear finite element program for simulation of transient one-dimensional flow and
solute transport in variably saturated porous media. The solution of the flow problem considers the effects
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of root uptake and hysteresis in the soil hydraulic properties. The solute transport equation incorporates
the processes of ionic or molecular diffusion, hydrodynamic dispersion, linear or nonlinear equilibrium
adsorption, and first-order decay. Boundary conditions for the flow and transport may be constant or
time-varying. For flow boundary conditions, HYDRUS can solve the steady-state flow equation in a single
step without the need of performing time-marching.
The solution of the flow equation in HYDRUS requires specification of the initial condition in terms of
pressure head or water content. Either first- or second-type boundary conditions can be imposed at the
soil surface. Alternatively, the upper boundary condition may be specified in terms of total amount of
surface applied water, combining both types of boundary conditions. The auxiliary condition at the lower
boundary is given in terms of imposed pressure head, zero head gradient, or imposed net drainage flux.
Type of boundary condition might change in time.
Soil hydraulic properties in HYDRUS can be described by the parametric functions of Van Genuchten (1978).
Uptake of water by plant roots includes evapotranspiration, a normalized root uptake distribution function,
and a pressure-salinity stress response function. HYDRUS uses the fully-implicit scheme to solve the set
of matrix equations for flow and transport. Nonlinearities in the flow equations are treated using Picard
iteration with under-relaxation. For solute transport, corrections are applied to the dispersion coefficient to
reduce numerical problems.
The HYDRUS program is a modification of the WORM program developed at the U.S. Salinity Laboratory.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications), demonstration/education
Documentation includes: model theory, user's instructions, example problems, program structure
and development, code listing, and verification/validation
Verification/validation: verification (analyt.solutions), laboratory data sets
Peer (independent) review: concepts, theory (math), documentation
References
Kool, J.B., and M.Th. van Genuchten. 1991. HYDRUS. One-Dimensional Variably Saturated Flow
and Transport Model Including Hysteresis and Root Water Uptake. U.S. Salinity Lab., U.S. Dept.
of Agric., Agric. Res. Service, Riverside, Calif.
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Appendix 4: Solute Transport in the Unsaturated Zone (requiring given head distribution)
IGWMC Key: 4350 Model Name: FEMTRAN
Author: Martinez, M.J.
Institution of Model Development: Sandia National Laboratories
Albuquerque, New Mexico
Code Custodian: Mario Martinez
Sandia National Laboratories, Fluid Mechanics and Heat Transfer Div.
Albuquerque, NM 87185
Abstract:
FEMTRAN is a two-dimensional finite element model to simulate cross-sectional advective radionuclide
transport in saturated/unsaturated porous media. The model considers chain-decay of the radionuclides.
It requires user prescribed heads.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications)
Documentation includes: model theory, user's instructions, example problems, program structure
and development, verification/validation
Verification/validation: verification (analyt.solutions)
Peer (independent) review: concepts, theory (math)
Availability: public domain
Remarks:
This model is based on a code developed by Duguid and Reeves (1976) and later updated by Yen
and Ward at Oak Ridge National Laboratory (FEMWASTE; IGWMC Key # 3371).
References:
Martinez, M.J. 1985. FEMTRAN - A Finite Element Computer Program for Simulating Radionuclide
Transport through Porous Media. SAND84-0747, Sandia National Lab., Albuquerque, New Mexico.
IGWMC Key: 3371 Model Name: FEMWASTE/FECWASTE
Authors: Yeh, G.T., and D.S. Ward
Institution of Model Development: Oak Ridge National Laboratory
Oak Ridge, Tennessee
Code Custodian: G.T. Yeh
Penn State University, Dept. of Civil Eng.
225 Sackett Bldg, University Park, PA 16802
Abstract:
FEMWASTE/FECWASTE are two-dimensional finite element models for transient simulation of areal or
cross-sectional transport of dissolved non-conservative constituents for a given velocity field in an
anisotropic, heterogeneous saturated or unsaturated porous medium. The velocity field is generated by
the accompanying FEMWATER/FECWATER two-dimensional flow models.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications)
Documentation includes: model theory, user's instructions, example problems, verification/validation
Verification/validation: verification (analyt.solutions)
A-4-1
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Peer (independent) review: concepts, theory (math)
Availability: public domain
Remarks:
FEMWASTE is a modified and updated version of a model published by Duguid and Reeves in 1976.
FECWASTE is a slightly modified and updated version of FEMWASTE. FEMWASTE and FECWASTE
use the velocity field generated by the models FEMWATER and FECWATER, respectively (IGWMC
key # 3370).
References:
Yeh, G.T. and D.S. Ward. 1981. FEMWASTE: A Finite-Element Model of a Waste Transport through
Porous Media. ORNL-5601. Oak Ridge Nat. Lab., Oak Ridge, Tenn.
Yeh, G.T. and R.H. Strand. 1982. FECWASTE: Users' Manual of a Finite-Element Computer Code
for Simulating Waste Transport through Saturated-Unsaturated Porous Media. ORNL/TM-7316. Oak
Ridge Nat. Lab., Oak Ridge, Tenn.
Duguid J. and M. Reeves. 1976. Material Transport through Saturated-Unsaturated Porous Media:
A Galerkin Finite Element Model. ORNL-4928. Oak Ridge Nat. Lab., Oak Ridge, Tenn.
Yeh, G.T. 1982. Training Course No.2: The Implementation of FEMWASTE (ORNL-5601) Computer
Program. Oak Ridge Nat Lab., Oak Ridge, Tenn.
Yeh, G.T. 1982. Training Course No.2: The Implementation of FEMWASTE (ORNL-5601) Computer
Program. NUREG/CR-2706, U.S. Nuclear Regulatory Commission, Washington, D.C.
IGWMC Key: 6130 Model Name: PESTAN
Authors: Enfield, C.G., R.F. Carsel, S.Z. Cohen, and T. Phan
Institution of Model Development: R.S. Kerr Environm. Res. Lab., U.S. EPA
Ada, Oklahoma.
Code Custodian: Center for Subsurface Modeling Support (CSMOS)
R.S. Kerr Environm. Res. Lab., U.S. EPA
P.O. Box 1198, Ada, Oklahoma 74820
Abstract:
PESTAN (PESticide Analytical Model) is an interactive analytical model, used for estimating organic chemical
movement in the unsaturated zone. The model is based on an analytical solution of the convective dispersive
solute transport equation for single layer homogeneous soils. It calculates vertical convective movement of
chemicals with linear equilibrium sorption and first-order (bio-) chemical decay. Hydrologic loading is based
on annual water balance. The primary application has been for pesticide screening.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications)
Documentation includes: model theory, user's instructions, example problems, verification/validation
Verification/validation: verification (analyt.solutions)
Peer (independent) review: concepts, theory (math)
Availability: public domain
A-4-2
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Remarks:
This model Is available from the International Ground Water Modeling Center, Colorado School of
Mines, Golden, CO 80401, USA.
References:
Enfield, D.G., R.F. Carsel, S.Z. Cohen, T. Phan, and D.M. Walters. 1982. Approximating Pollutant
Transport to Ground Water. Ground Water, Vol. 20(6), pp. 711-722.
Donigian, Jr., A.S., and P.S.C. Rao. 1986. Overview of Terrestrial Processes and Modeling. In: S.C.
Hern and S.M. Melancon (eds.), Vadose Zone Modeling of Organic Polllutants. Lewis Publishers,
Chelsea, Michigan.
IGWMC Key: 6225 Model Name: CHAIN
Authors: van Genuchten, M. A.
Institution of Model Development: USDA Salinity Lab., Riverside, Calif.
Code Custodian: M.Th. van Genuchten
USDA Salinity Laboratory, 4500 Glenwood Drive, Riverside, CA 92501
Abstract:
The CHAIN model simulates multi-ion transport across the unsaturated zone using an analytical procedure.
The model includes longitudinal dispersion and first-order decay. It calculates the time history of chemical
concentration exiting the unsaturated zone.
Model developed for: research (e.g. hypothesis/theory testing)
Documentation includes: model theory, user's instructions, example problems, program structure
and development, verification/validation
Verification/validation: laboratory data sets
Peer (independent) review: concepts, theory (math)
Availability: public domain
IGWMC Key: 5620 Model Name: SUMMERS
Authors: Summers, K., S. Gherini, and C. Chen
Institution of Model Development: Tetra Tech, Inc., Lafayette, Calif.
Code Custodian: U.S. Environmental Protection Agency
Environmental Research Laboratory, Athens, GA 30613
Abstract:
The SUMMERS model refers to a combination of an analytical solution for one-dimensional, non-dispersive
transport in soil due the continuous release at the surface, and a mass-balance evaluation of the subsequent
mixing in an underlying aquifer. This model can be used to estimate the contaminant concentrations in the
soil which will produce ground-water contaminant concentrations above acceptable levels. The resultant
soil concentrations can then be used as guidelines in estimating boundaries or extent of soil contamination
and specifying soil cleanup goals for remediation. The model utilizes steady-state water movement and
equilibrium partitioning of the contaminant in the unsaturated zone. For assessment of the concentration
in the aquifer, the model assumes a constant flux from the surface source to the aquifer and instantaneous,
complete mixing in the aquifer. The model does not account for volatilization, and should not be used for
volatile compounds.
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Model developed for: general use (e.g. in field applications)
Availability: can be coded by user
References:
Summers, K., S. Gherini, and C. Chen. 1980. Methodology to Evaluate the Potential for Ground
Water Contamination from Geothermal Fluid Releases; pp. 67-73. EPA-600/7-80-117, U.S. EPA,
ORD/IERL, Cincinnati, Ohio.
IGWMC Key: 5661 Model Name: FLAME
Authors: Baca, R.G., and S.O. Magnuson
Institution of Model Development: Idaho Nat. Eng. Lab., EG&G, Idaho Falls, Idaho
Code Custodian: Baca, R.G.
Idaho Nat. Eng. Lab., EG&G Idaho, Inc., P.O. Box 1625, Idaho Falls, Idaho 83415
Abstract:
FLAME is a finite element code designed to simulate two-dimensional, cross-sectional subsurface transport
of low-concentration contaminants in either time-dependent or steady-state, known flow field in a highly
heterogeneous variably-saturated porous media with complex stratigraphy. The code can be applied to
two-dimensional transport in an arid vadose zone or in an unconfined aquifer. FLAME handles
advective-dispersive transport, equilibrium sorption using a linear isotherm, first-order decay, and a complex
source/sink term. It accommodates advection-dominated mass transport. In addition, the code has the
capability to describe transport processes in a porous media with discrete fractures. It describes the mass
transfer between the porous media and discrete fractures.
Model developed for: general use (e.g. in field applications)
Documentation includes: model theory, user's instructions, example problems, verification/validation
Verification/validation: verification (analyt.solutions), code intercomparison
Peer (independent) review: concepts, theory (math)
Remarks:
FLAME can handle both Dirichlet and Neumann transport boundary conditions. The code can
model transport of contaminants in a single phase, being either liquid, gaseous (e.g. organic
vapors), or colloidal. The modified equation approach of Fletcher with a build-in dissipation
mechanism is used to dampen oscillations in a convection dominated transport system. The
resulting finite element matrix equations are solved by a Gaussian elimination procedure without
pivoting. Two solvers are used: 1) standard band solver utilizing a skyline storage scheme, and 2)
frontal method.
References:
Baca. R.G., and S.O. Magnuson. 1988. FLAME - A Finite Element Computer Code for Contaminant
Transport in Variably-Saturated Media. EGG-GEO-10329, Idaho Nat. Eng. Lab., EG&G, Idaho Falls,
Idaho.
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IGWMC Key: 5690 Model Name: VLEACH (Vadose Zone LEACHing Model)
Author: J. Turin
Institution of Model Development: CH2M-HHI, Reading, Calif.
Code Custodian: see remarks
Abstract:
VLEACH is a relatively simple one-dimensional finite difference model designed to simulate leaching of a
volatile, adsorbed contaminant through the vadose zone. It can be used to simulate the transport of any
non-reactive chemical that displays linear partitioning behavior. In particular, VLEACH simulates downward
liquid-phase advection, solid-phase sorption, gas diffusion in the vapor phase, and three-phase equilibrium.
The contaminant mass within each model cell is partitioned among liquid (dissolved in water), vapor, and
solid phases. The model assumes a homogeneous porous medium with steady flow and no dispersion.
There is no in-situ degradation or production, and free product is not present.
Model developed for: general use (e.g. in field applications)
Documentation includes: model theory, user's instructions, example problems, and program
structure and development.
Availability: public domain
Remarks:
Input data for VLEACH consists of: organic carbon coefficient (Koc), Henry's Law constant (Kh), the
aqueous solubility and the free air diffusion coefficient. The input soil properties are dry bulk
density, total porosity, volumetric water content and organic carbon fraction, and site-specific input
parameters such as recharge rate and depth to groundwater.
This software is available from: Center for Subsurface Modeling Support (CSMOS), R.S. Kerr
Environmental Research Laboratory, U.S. Environmental Protection Agency, P.O. Box 1198, Ada,
OK 74820, Phone: 405/332-8800.
References:
Turin, J. August 1990. VLEACH: A One-Dimensional Finite Difference Vadose Zone Leach Model.
Report prepared for U.S. EPA, Region 9., CH2M Hill, Reading, Calif.
A-4-5
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Appendix 5: Flow and Heat Transport in the Unsaturated Zone
IGWMC Key: 2582 Model Name: TOUGH (Transport of Unsaturated Groundwater and Heat)
Authors: Pruess, K., Y.W. Tsang, and J.S.Y. Wang
Institution of Model Development: Lawrence Berkeley Laboratory
Berkeley, California
Code Custodian: Pruess, K.
Lawrence Berkeley Laboratory, Earth Science Division
Mailstop 50E LBL, University of California
Berkeley, CA 94720
Abstract:
TOUGH is a multi-dimensional integrated finite difference model for transient simulation of the coupled
transport of water, air, vapor and heat transport in fractured Unsaturated porous media. The model includes
convection, condensation, capillary forces, evapotranspiration, heat conduction and diffusion, change of
phase, adsorption, fluid compression, dissolution of air in liquid, and buoyancy. The gas and liquid phase
flow of air and water, and heat transport are solved in a fully coupled manner.
Model developed for: research (e.g. hypothesis/theory testing)
Documentation includes: model theory, user's instructions, example problems, program structure
and development, code listing, verification/validation
Verification/validation: verification (analyt.solutions), laboratory data sets, code intercomparison
Peer (independent) review: concepts, theory (math), documentation
Availability: public domain
Remarks:
The TOUGH code is available with full documentation from:
National Energy Software Center (NESC)
Argonne National Lab.
9700 South Cass Ave., Argonne, IL 60439
To evaluate how hysteretic capillary pressure-liquid saturation relation may effect the flow and liquid
saturation distribution in a fractured rock system, Niemi and Bodvarsson (1988; see references)
included capillary hysteresis in the numerical flow simulator TOUGH. Material properties used for
these evaluations represent the densely welded tuff of the Yucca Mountain site in Nevada.
A fracture network generator based on the MINC concept is available for TOUGH (see Pruess,
1983).
TOUGH was tested by Sandia National Laboratories and results were compared to analytical
solutions, laboratory data sets, and the programs NORIA and PETROS. TOUGH was capable of
solving most of the problems and out-performed the other codes. However, it had the most
difficulty with numerical dispersion. TOUGH'S greatest weakness is the way it handles boundary
conditions especially when boundary conditions are mixed in the form of prescribed mass flux and
constant temperature (or similar conditions).
Relative permeability must be input as an analytical function. The user is given the choice of a linear
function, "Corey's curves", "Grant's curves", Fatt and Kilikoff functions, Sandia functions, or Verma
functions. Capillary pressure functions must also be input as analytical functions. The user may
specify a linear function, Milly's function, Leverett's function, or the Sandia function.
A-5-1
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References:
Pruess, K., '1984. TOUGH - A Numerical Model for Strongly Heat Driven Flow in Partially Saturated
Media. LF4L Earth Sciences Div. Annual Rept., Lawrence Berkeley Laboratory, Univ. of Calif.,
Berkeley, Calif., pp. 39-41.
Pruess, K., Y.W. Tsang, and J.S.Y. Wang. 1984. Modeling of Strongly Heat Driven Flow in Partially
Saturated Fractured Porous Media. LBL-18552, Lawrence Berkeley Laboratory, Univ. of Calif.,
Berkeley, Calif.
Pruess, K. and J.S.Y. Wang, 1984. TOUGH - A Numerical Model for Nonisothermal Unsaturated
Flow to Study Waste Canister Heating Effects. In: G.L. McVay (ed.) Mat. Res. Soc. Symp. Proc.,
Scientific Basis for Nuclear Waste Management, North Holland, New York, Vol. 26, pp. 1031-1038.
Pruess, K, Y.W. Tsang, and J.S.Y. Wang. 1984. Modeling of Strongly Heat-Driven Flow in Partially
Saturated Fractured Porous Media. LBL-17490, Lawrence Berkeley Laboratory, Univ. of Calif.,
Berkeley, Calif.
Pruess, K. 1987. TOUGH User's Guide. NUREG/CR-4645, U.S. Nuclear Regulatory Commission,
Washington, D.C.
Pruess, K. 1986. TOUGH-Users Guide. LBL-20700, Lawrence Berkeley Laboratory, Univ. of Calif.,
Berkeley, Calif.
Pruess, K. 1983. GMINC-- A Mesh Generator for Flow Simulations in Fractured Reservoirs.
LBL-15227, Lawrence Berkeley Laboratory, Univ. of Calif., Berkeley, Calif.
Niemi, A., and G.S. Bodvarsson. 1988. Preliminary Capillary Hysteresis Simulations in Fractured
Rocks, Yucca Mountain, Nevada. Journ. of Contaminant Hydrol., Vol. 3, pp. 277-291.
IGWMC Key: 2950 Model Name: TRANS
Authors: Walker, W.R., J.D. Sabey, and D.R. Hampton
Institution of Model Development: Colorado State University
Fort Collins, Colorado
Code Custodian: Hampton, D.R., Western Michigan University
Geology Department, Kalamazoo, Ml 49008
Abstract:
TRANS is a finite element model for transient simulation of two-dimensional, horizontal, cross-sectional,or
axial symmetric, coupled flow of heat and moisture in partially or fully saturated porous media, especially
for assessment of buried thermal reservoirs and the heat exchange piping internal to the reservoirs.
Model developed for: research (e.g. hypothesis/theory testing)
Documentation includes: model theory, user's instructions
Availability: public domain
References:
Walker, W.R., J.D. Sabey and D.R. Hampton. 1981. Studies of Heat Transfer and Water Migration
in Soils. Rept. Solar Energy Lab., Dept of Agri. and Chem. Eng., Colorado State University, Fort
Collins, Colorado.
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IGWMC Key: 3375 Model Name: MATTUM
Authors: Yeh, G.T. and R.J. Luxmoore
Institution of Model Development: Oak Ridge National Laboratory
Oak Ridge, Tennessee
Code Custodian: Yeh, G.T.
Penn State University, Dept. of Civil Eng.
225 Sackett Bldg, University Park, PA 16802
Abstract:
MATTUM is a three-dimensional model for simulating moisture and thermal transport in unsaturated porous
media. The model solves both the flow equation and the heat transport equation under unsaturated water
conditions using the integrated compartment method. The entire unsaturated zone is divided in a number
of compartment of different sizes and shapes. The Philip-de Vries equations governing moisture movement
and heat transfer are integrated over each of the compartments to yield a system of nonlinear ordinary
differential equations. There three optional time integration schemes: split explicit, implicit pointwise iteration,
and matrix inversion iteration.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications)
Documentation includes: model theory, user's instructions, example problems, code listing,
verification/validation
Verification/validation: verification (analyt.solutions)
Peer (independent) review: concepts, theory (math)
References:
Yeh, G.T. and R.J. Luxmoore. 1983. MATTUM: A Multidimensional Model for Simulating Moisture
and Thermal Transport in Unsaturated Porous Media. ORNL-5888, Oak Ridge National Laboratory,
Oak Ridge, Tennessee.
IGWMC Key: 3590 Model Name: SPLASHWATER
Author: Milly, P.
Institution of Model Development: Princeton University, Water Resources Program
Dept. of Civil Engineering, Princeton, NJ 08544
Code Custodian: Milly, P.C.D.
Princeton University, Dept. of Civil Engineering
Princeton, NJ 08544
Abstract:
SPLASHWATER is a finite element model for simulation of coupled heat and moisture fields in the
unsaturated zone. The model includes evapotranspiration, hysteresis, and heat convection and conduction.
Model developed for: research (e.g. hypothesis/theory testing)
Documentation includes: model theory, user's instructions, example problems, code listing,
verification/validation
Verification/validation: verification (analytsolutions)
Availability: restricted public domain
A-5-3
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References:
Milly, P.C.D. 1982. Moisture and Heat Transport in Hysteretic, Inhomogeneous Porous Media: A
Matric Head-Based Formulation and Numerical Model. Water Resourc. Res., Vol. 18(3), pp. 489-498.
Milly, P.C.D. and P.S. Eagleson. 1980. The Coupled Transport of Water and Heat in a Vertical Soil
Column Under Atmospheric Excitation. MIT Report No. 258, Massachusetts Inst. of Technology,
Cambridge, Mass.
IGWMC Key: 5660 Model Name: FLASH
Authors: Baca, R.G., and S.O. Magnuson
Institution of Model Development: Idaho National Engineering Laboratory
EG&G, Inc., P.O. Box 1625, Idaho Falls, Idaho 83415
Code Custodian: Baca, R.G.
Idaho National Engineering Laboratory
Subsurface and Environm. Modeling Unit, Geoscience Group,
EG&G, Inc, P.O. Box 1625, Idaho Falls, Idaho 83415.
Abstract:
FLASH is a finite element model for simulation of two-dimensional, cross-sectional, variably saturated fluid
flow in fractured porous media at an arid site, together with two-dimensional, horizontal, saturated flow in
an underlying unconfined aquifer. In addition, the code has the capability to simulate heat conduction in
the vadose zone. The Richard's equation for variably saturated flow is solved iteratively using a Picard or
Newton iteration technique, the unconfined flow equation is solved using Newton-Raphson iteration. The
variably saturated module handles 1st, 2nd and 3rd type b.c.'s, the saturated module only 1st and 2nd type
b.c.'s. The FLASH code can be interfaced with the FLAME code to simulate contaminant transport in the
subsurface.
Model developed for: general use (e.g. in field applications)
Documentation includes: model theory, user's instructions, example problems, program structure
and development, verification/validation
Verification/validation: verification (analyt.solutions), code intercomparison
Peer (independent) review: concepts, theory (math)
Availability: public domain
Remarks:
The FLASH and FLAME codes are extensions and refinements of the MAGNUM fluid flow code and
the CHAINT contaminant transport code, respectively.
References:
Baca, R.G., and S.O. Magnuson. 1992. FLASH - A Finite Element Computer Code for Variably
Saturated Flow. EGG-GEO-10274, Idaho National Engineering Laboratory, Idaho Falls, Idaho.
A-5-4
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Appendix 6: Flow, Solute Transport and Heat Transport in the Unsaturated Zone
IGWMC Key: 3234 Model Name: VADOSE
Authors: Sagar, B.
Institution of Model Development: Analytic & Computational Research.lnc.
Los Angeles, California
Code Custodian: B. Sagar
Southwest Research Inst., Div. 20
6220 Culebra Road, P.O. Drawer 0510
San Antonio, TX 38510
Abstract:
VADOSE is an integrated finite difference model for analysis of steady or transient, two-dimensional area),
cross-sectional or radial simulation of coupled density-dependent transport of moisture, heat and solutes
in variably-saturated, heterogeneous, anisotropic porous media.
Model developed for: research (e.g. hypothesis/theory testing)
Documentation includes: model theory, user's instructions, example problems
Availability: proprietary, license
IGWMC Key: 3235 Model Name: FLOTRA
Authors: Sagar, B.
Institution of Model Development: Analytic & Computational Research, Inc.
Los Angeles, California
Code Custodian: B. Sagar
Southwest Research Inst., Div. 20
6220 Culebra Road, P.O. Drawer 0510
San Antonio, TX 38510
Abstract:
FLOTRA is an integrated finite difference model for simulation of steady or transient, two-dimensional areal,
cross-sectional or radial, density- dependent flow, heat and mass transport in variably saturated, anisotropic,
heterogeneous, deformable porous media.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications)
Documentation includes: model theory, user's instructions, example problems
Availability: proprietary, license
IGWMC Key: 3830 Model Name: SUTRA
Authors: Voss, C.I.
Institution of Model Development: U.S. Geological Survey
Water Resources Div., National Center
Reston, Virginia
Code Custodian: Voss, C.I.
U.S. Geological Survey, 431 National Center, Reston, VA 22092
Abstract:
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SUTRA (Saturated-Unsaturated TRAnsport) simulates transient or steady-state, two-dimensional, variably
saturated, fluid density dependent ground water flow with transport of energy or chemically reactive species
solute transport. The model employs a hybrid finite-element and integrated-finite-difference method to
approximate the coupled equations. Solute transport include advection, dispersion, diffusion, equilibrium
adsorption on the porous matrix, and both first-order and zero-order decay or production. Energy transport
may take place in both the solid matrix and the liquid phase. SUTRA may be employed in both areal
(horizontal) and cross-sectional mode for saturated systems or in cross-sectional mode only for unsaturated
systems, (see remarks).
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications), demonstration/education
Documentation includes: model theory, user's instructions, example problems, program structure
and development, code listing, verification/validation
Verification/validation: verification (analyt.solutions), laboratory data sets
Peer (independent) review: concepts, theory (math), documentation
Availability: public domain, proprietary, purchase
Remarks:
SUTRA provides, as preliminary calculated results, fluid pressures and either solute concentrations
or temperatures. Mesh construction is flexible for arbitrary geometries employing quadrilateral finite
elements in Cartesian or radial-cylindrical coordinates. The mesh might be coarsened through the
use of pinch nodes. Boundary conditions, sources and sinks may be time dependent. The model
has a rest art option. Options are also available to print fluid velocities, and fluid mass, and solute
mass or energy budgets for the system. SUTRA's numerical algorithms are not specifically
applicable to non-linearities of unsaturated flow. Therefor SUTRA, as distributed by the USGS,
requires fine spatial and temporal discretization for unsaturated flow. The user can replace the
included function for unsaturated flow by others, and recompile the code.
An extension of the code SUTRA is the code SATRA-CHEM by Lewis (1984; 1986; see IGWMC Key
# 3831). It includes sorption, ion exchange and equilibrium chemistry. The nonlinear components
resulting from these chemical processes are reduced into two time-dependent variables that
essentially plug into a general form of the classic advection-dispersion equation.
A main-frame version of SUTRA and an extended memory IBM PC-386 version is available from the
International Ground Water Modeling Center, Colorado School of Mines, Golden, CO 80401.
An IBM PC/386 extended memory version of this model is also available from Geraghty & Miller,
Inc., Modeling Group, 10700 Parkridge Blvd, # 600, Reston, VA 22091.
The new version of SUTRA (USGS, June 1990) includes a post-processor SUTRAPLOT, based on
an contouring algorithm developed by Aden Harbough.
References:
Voss, C.I. 1984. SUTRA: A Finite Element Simulation Model for Saturated-Unsaturated Fluid
Density-Dependent Ground Water Flow with Energy Transport or Chemically Reactive Single Species
Solute Transport. Water-Resources Investigations Report 84-4369, U.S. Geological Survey, Reston,
Virginia.
Souza, W.R. 1987. Documentation of a Graphical Display Program for SUTRA Finite-Element
Simulation Model. Water-Resources Investigations Report 87-4245, U.S. Geological Survey,
Washington, D.C.
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Wagner, J., and Ruiz-Calzada, C.E., (Date Unknown). Evaluation of Models for Unsaturated -
Saturated Flow and Solute Transport. Cooperative agreement CR 81114-01-2 with Robert S. Kerr
Environmental Research Laboratory and the School of Chemical Engineering, Oklahoma State
University, Sillwater, OK.
IGWMC Key: 4550 Model Name: MOTIF (Model of Transport in Fractured/Porous Media)
Authors: Guvanasen, V.
Institution of Model Development: Atomic Energy of Canada, Ltd.
Whiteshell Nuclear Research Establishment
Pinawa, Manitoba, Canada
Code Custodian: Tin Chan
Atomic Energy of Canada, Ltd.
Whiteshell Nuclear Research Estb.
Pinawa, Manitoba, Canada ROE110
Abstract:
MOTIF is a finite element model to simulate one-, two-, and three-dimensional coupled processes of
saturated or unsaturated fluid flow, conductive and convective heat transport, brine transport and single
species radionuclide transport in a compressible rock of low permeability intersected with a few major
fractures. The model includes diffusion into the rock matrix.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications)
Documentation includes: model theory, user's instructions, verification/validation
Verification/validation: verification (analyt.solutions), code intercomparison
Availability: proprietary, license
Remarks:
MOTIF is especially suitable for modeling fractured rock mass since the 4-noded planar elements
can be used to simulate flow in arbitrarily oriented planar fractures or fracture zones in a 3D model.
The code has been verified among others by comparison with closed-form solutions in the
HYDROCOIN project, (see Chanel Al. 1986). It has been subject to AECL's internal quality
assurance.
References:
Chan, T., V. Guvanasen and J.A. Reid. 1985. Numerical Modelling of Coupled Fluid, Heat and
Solute Transport in Deformable Fractured Rock. International Symposium on Coupled Processes
Affecting the Performance of a Nuclear Waste Repository, Berkeley, September, 18-20, 1985.
Lawrence Berkeley Laboratory, Univ. of Calif., Berkeley, Calif.
Chan, T., N.W. Scheierand J.A.K. Reid. 1986. Finite Element Thermohydrogeological Modeling for
Canadian Nuclear Fuel Waste Management. Second International Conference on Radioactive Waste
Management, Winnipeg, September 1986.
Davison, C.C. and V. Guvanasen, 1985. Hydrogeological Characterization Modelling and Monitoring
of the Site of Canada's Underground Research Laboratory. In: Proceed. Hydrogeology of Rocks
of Low Permeability, IAH 17th Internat. Congress, Tuscon, Arizona, January 7-11, 1985. Internat.
Assoc. of Hydrogeologists.
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Chan, T., V. Guvanasen and B. Nakka. 1986. Verification of the MOTIF Finite Element Code Using
HYDROCOIN Level 1 Cases 1,2, and 4. Atomic Energy of Canada, Ltd., Pinawa, Manitoba.
Guvanasen, V. 1984. Development of a Finite Element Code and its Application to Geoscience
Research. In: Proceedings 17th Information Meeting of the Nuclear Waste Management Program.
Atomic Energy of Canada, Ltd., Technical Record TR-199, pp. 554-566.
Chan, T., V. Guvanasen, and J.A.V. Rein. 1987. Numerical Modeling of Coupled Fluid, Heat and
Solute Transport in Deformable Fractured Rock. In: C.F. Tsang (ed.), Coupled Processes
Associated with Nuclear Waste Repositories, pp. 605-625. Academic Press, Orlando, Florida.
Chan, T. 1989. An Overview of Groundwater Flow and Radionuclide Transport Modeling in the
Canadian Nuclear Fuel Waste Management Program. In: B.E. Buxton (ed.), Geostatistical
Sensitivity and Uncertainty Methods for Groundwater Flow and Radionuclide Transport Modeling,
pp.39-62. Battelle Press, Battelle Memorial Institute, Columbus, Ohio.
IGWMC Key: 5031 Model Name: CTSPAC
Authors: Lindstrom, FT., D.E. Cawlfield, and L. Boersma
Institution of Model Development: Oregon State University, Dept. of Soil Science
Corvallis, Oregon
Code Custodian: L. Boersma
Dept. of Soil Science, Oregon State University
Corvallis, OR 97331
Abstract:
CTSPAC is an one-dimensional numerical model that couples the flow of water and the transport of heat and
solutes in layered soils with the uptake and transport of water and solutes in plants. Initial root distribution
is specified. The rate of uptake is a function of the environmental conditions that determine the plant's
transpiration rate. Water transport in the plant is based on water potential and pressure gradients according
to Munch pressure flow hypothesis. The model was developed for assessing risks involved in the use of
xenobiotic chemicals. It allows an evaluation of the rate of uptake of such chemicals from the soil solution
and the accumulation in the various plant parts.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications)
Documentation includes: model theory, user's instructions, example problems
Peer (independent) review: concepts, theory (math)
Availability: public domain
References:
Lindstrom, FT., D.E. Cawlfield, and L. Boersma. 1988. CTSPAC: Mathematical Model for Coupled
Transport of Water, Solutes, and Heat in the Soil-Plant-Atmosphere Continuum. EPA/600/3-88/030,
U.S. Environmental Protection Agency, Environm. Research. Lab., Corvallis, Oregon.
Boersma, L, FT. Lindstrom, C. McFarlane and E.L. McCoy. 1988. Model of Coupled Transport of
Water and Solutes in Plants. Spec. Report No. 818. Agric. Experim. Station, Oregon State Univ.,
Corvallis, Oregon.
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IGWMC Key: 3238 Model Name: PORFLOW-3D
Author: Runchal, A.K.
Institution of Model Development: Analytic and Computational Research, Inc., Bel Air, Calif.
Code Custodian: Akshai Runchal
1931 Stradella Road, Bel Air, CA 90077
Abstract:
PORFLOW-3D is an integrated finite difference model to simulate coupled transient or steady-state,
multiphase, fluid flow, and heat, salinity, or chemical species transport in variably saturated porous or
fractured, anisotropic and heterogeneous media. The program facilitates arbitrary sources or sinks in
three-dimensional cartesian or axisymmetric (cylindrical) geometry. The user interface is based on the
FREEFORM language using simple English-like commands. The software includes the ARCPLOT graphic
post processor.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications), demonstration/education
Documentation includes: model theory, user's instructions, example problems, verification/validation
Verification/validation: verification (analyt.solutions)
Availability: proprietary, license
Remarks:
PORFLOW II and PORFLOW III have been used extensively in real life problem solving. A version
of this model is being used to simulate the near-field behavior of high level nuclear waste repository
in basalt.
PORFLOW II and PORFLOW III provide optional coupling with thermo-mechanical stress model,
developed by the same author. A version of the PORFLOW series, PORFLOW-R, provides special
features for simulation of transport processes around high-level waste repositories. These include,
for example, an option to calculate the instantaneous or cumulative nuclide flux crossing a given
boundary.
See also PORFLO (IGWMC Key # 3790), PORFLOW-2D (IGWMC Key # 3233), and PORFLOW-3D
(IGWMC Key # 3238).
References:
Runchal, A.K. 1982. PORFLOW-R: A Mathematical Model for Coupled Ground Water Flow, Heat
Transfer and Radionuclide Transport in Porous Media. Techn. Rept. Rep-014, Analytic &
Computational Research, Inc., West Los Angeles, California.
Runchal, A.K. 1981. PORFLOW-F: A Mathematical Model for Ground Water Flow with Heat
Transfer, Freezing, Thawing and Atmospheric Heat Exchange, Volume I - Theory. Techn Report
REP-006a, Analytic & Computational Research, Inc., West Los Angeles, California.
Runchal, A.K., and G. Hocking. 1981. An Equivalent Continuum Model for Fluid Flow, Heat and
Mass Transport in Geological Materials. Paper 81-HT-54, ASME, 20th Joint ASME/AIChE National
Heat Transfer Conference, Milwaukee, Wisconsin, August 2-5.
Runchal, A.K. 1982. Mathematical Basis of Porous Media Flow, Heat and Mass Transfer. Techn.
Report REP-008, Analytic & Computational Research, Inc., West Los Angeles, Calif.
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Runchal, A.K. 1982. The Density and Viscosity Relations for Water. Techn. Report REP-009,
Analytic & Computational Research, Inc., West Los Angeles, Calif.
Runchal, A.K. 1987. Theory and Application of the PORFLOW Model for Analysis of Coupled Fluid
Flow, Heat and Radionuclide Transport in Porous Media. In: C.-F. Tsang (ed.), Coupled Processes
Associated with Nuclear Waste Repositories, Academic Press, New York, New York, pp. 495-516.
IGWMC Key: 5213 Model Name: TDFD10 (Two-Dimensional Finite Difference 1st Order sorption)
Authors: Slotta, LS.
Institution of Model Development: Slotta Engineering Associates, Inc, Corvallis, Oregon
Code Custodian: Jala) Heydarpour
Slotta Engineering Associates, Inc.
P.O. Box 1376, Corvallis, OR 97339
Abstract:
TDFD10 is a two-dimensional model for simultaneous simulation of movement of moisture, transport of heat,
and transport and fate of a contaminant in a shallow unconfined aquifer. The porous medium may be
heterogeneous. The coupled system of non-linear unsaturated/saturated moisture flow and heat and
chemical transport are solved using a finite difference approximation. The porous medium is partitioned in
three fractions: sand, clay, and organic material, with for each fraction first-order sorption kinetics included.
Time integration is performed using the backward Euler method. Dynamic boundary conditions at the
air-porous medium interface are included. A variety of first- and second-type boundary conditions are
included.
Model developed for: general use (e.g. in field applications)
Documentation includes: user's instructions, example problems
IGWMC Key: 5860 Model Name: NEWTMC
Authors: Lindstrom, FT. (1), and FT. Piver, FT.
Institution of Model Development: 1) Dept. of Math., Oregon State Univ., Corvallis;
2) Nat. Inst. of Health, Research Triangle Park, NC.
Code Custodian: Lindstrom, FT.
Dept. of Mathematics, Oregon State Univ., Corvallis, OR 97331
Abstract:
NEWTMC is an one-dimensional mass balance model for simulating the transport and fate of nonionizable
organic compounds in unsaturated/saturated porous media. Using the principles of water mass,
momentum, neat energy and chemical mass balance, the model solves simultaneously for moisture,
temperature and liquid phase chemical concentration. The model uses a dynamic free boundary to
represent the air-soil interface and a prescribed water table height as lower boundary. The model allows
for elaborate simulation of air conditions at the air-soil interface, allowing the boundary conditions to be
dependent on the air conditions. Chemicals may be introduced via incoming air (vapor phase), rain water,
inflow from the water table, or initially distributed within the soil column.
Model developed for: research (e.g. hypothesis/theory testing)
Documentation includes: model theory, user's instructions, example problems, verification/validation
Verification/validation: laboratory data sets
Peer (independent) review: concepts, theory (math)
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Availability: public domain
References:
Lindstrom, FT., and W.T. Piver. 1985. A Mathematical Model for the Transport and Fate of Organic
Chemicals in Unsaturated/Saturated Soils. Environm. Health Perspectives, Vol. 60, pp. 11-28.
Lindstrom, FT., and WT. Piver. 1984. A Mathematical Model for Simulating the Fate of Toxic
Chemicals in a Simple Terrestrial Microcosm. Techn. Rept. 51, Dept. of Math, and Stat., Oregon
State Univ., Corvallis, Oregon.
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Appendix 7: Parameter Estimation for Flow and Transport in the Unsaturated Zone
IGWMC Key: 3433 Model Name: ONESTEP
Authors: Kool, J.B., J.C. Parker, and M.Th. Van Genuchten.
Institution of Model Development: Virginia Polytechn. Inst.
Blacksburg, Virginia
Code Custodian: J.C. Parker
Virginia Polytechn. Inst.
245 Smyth Hall, Blacksburg, VA 24061
Abstract:
ONESTEP is a nonlinear parameter estimation model for evaluating soil hydraulic properties from one-step
outflow experiments in the one-dimensional flow. The program estimates parameters in the van Genuchten
soil hydraulic property model from measurements of cumulative outflow with time during one-step
experiments. The program combines non-linear optimization with a Galerkin finite element model.
Model developed for: research (e.g. hypothesis/theory testing), demonstration/education
Documentation includes: model theory, user's instructions, example problems, verification/validation
Verification/validation: verification (analyt.solutions), laboratory data sets
Peer (independent) review: concepts, theory (math)
Availability: proprietary, purchase
Remarks:
An IBM-PC version is available from the International Ground Water Modeling Center, Colorado
School of Mines, Golden, CO 80401.
References:
Kool, J.B., J.C. Parker, and M.Th. Van Genuchten. 1985. ONESTEP: A Nonlinear Parameter
Estimation Program for Evaluating Soil Hydraulic Properties from One-Step Outflow Experiments.
Bulletin 85-3, Virginia Polytechn. Inst., Blacksburg, Virginia.
IGWMC Key: 6330 Model Name: SOIL
Authors: El-Kadi, A.I.
Institution of Model Development: International Ground Water Modeling Center
Holcomb Research Institute, Indianapolis, Indiana
Code Custodian: International Ground Water Modeling Center
Colorado School of Mines, Golden, CO 80401
Abstract:
SOIL estimates the parameters of the soil hydraulic functions. For the soil-water characteristic function the
user can choose from the methods of Brooks and Corey (1964), Brutsaert (1966), Vauclin et al. (1979), and
van Genuchten (1978). The parameters for the chosen function are obtained using non-linear least-squares
analysis. The unsaturated hydraulic conductivity function is estimated by the series-parallel model of Childs
and Collis-George (1950) and is obtained by straight-line fitting on a log-log curve. With the derived
parameters, the program computes for selected pressures the observed and fitted moisture contents and
the soil hydraulic properties. The results are plotted graphically on screen. If saturated hydraulic
conductivity is unknown the program provides an estimated value. The menu-driven, user-interactive code
requires as input pairs of measured water content and suction, and the saturated water content that
corresponds with zero suction.
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Model developed for: general use (e.g. in field applications)
Documentation includes: model theory, user's instructions, example problems, code listing
Availability: public domain
References:
El-Kadi, A.I. 1987. Estimating the Parameters of Soil Hydraulic Properties SOIL, Microcomputer
Interactive Version. BAS-14, Internal. Ground Water Modeling Center, Holcomb Research Inst.,
Indianapolis, Indiana.
El-Kadi, A.I. 1984. Automated Estimation of the Parameters of Soil Hydraulic Properties. GWMI
84-12, Internat. Ground Water Modeling Center, Holcomb Research Inst., Indianapolis, Indiana.
IGWMC Key: 6170 Model Name: FP
Authors: Su, C., and R.H. Brooks
Institution of Model Development: Oregon State University, Dept. of Agricultural Eng.,
Corvallis, Oregon
Code Custodian: Dept. of Agricultural Eng., Oregon State University
Corvallis, OR 97331
Abstract:
FP is a program to determine the parameters of the retention function (the soil-water characteristic function)
from experimental data. Based upon the Pearson Type VIII distribution function, a general retention function
which relates the saturation to the capillary pressure in distributed soils has been formulated. This simple,
yet complete function has been shown to describe the imbibition as well as the drainage branch of the
retention curve. It is defined by four readily assessed parameters that either have physical significance
themselves or may be used to determine some hydraulic properties of the soil. Please see "Remarks" for
more information.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications)
Documentation includes: model theory, user's instructions, example problems
Availability: public domain
Remarks:
With the assumption that the Burdine integrals are adequate, a relative permeability function has
been derived through the substitution of the retention function for the integrands in the Burdine
Integrals. The permeability function is expressed in terms of the incomplete Beta function ration
whose value may be conveniently found in some mathematical tables.
A general pore-sized distribution function of soils has been obtained from the retention function.
The derivation of the pore-size distribution function enables more rigorous examination and further
exploration of the theories concerning water movement in partially saturated soils. In this respect,
an explanation of the phenomenon of air entrapment during imbibition has been offered through an
energy concept based upon the pore-size distribution function along with the retention function.
Two criteria of affinity have been established for porous media. Media are said to be affine if their
corresponding pore-size distribution parameters are identical. The scaling factor for the external
dimension of the model has been chosen to be the capillary pressure head at the inflection point
of the retention curve, whose value is always finite. The analysis of the effect of the pore-size
distribution parameters upon the retention, permeability, and diffusivity curves shows that the
parameter governing the downward concavity of the retention curve is as important as that
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governing the upward concavity when it comes to computing the permeability values from the
retention data.
This model is available from the International Ground Water Modeling Center, Colorado School of
Mines, Golden, CO 80401.
References:
Su, C., and R.H. Brooks. 1976. Hydraulic Functions of Soils from Physical Experiments. WRRI-41,
Dept. of Agricultural Eng., Oregon State Univ., Corvallis, Oregon.
IGWMC Key: 6226 Model Name: SOHYP
Authors: Van Genuchten, M. Th.
Institution of Model Development: Princeton University, Dept. of Civil Eng.
Princeton, New Jersey
Code Custodian: M.Th. van Genuchten
USDA Salinity Laboratory, 4500 Glenwood Drive, Riverside, CA 92501
Abstract:
SOHYP is an analytical model for calculation of the unsaturated hydraulic conductivity function using soil
moisture retention data. The basis of SOHYP is a relatively simple equation for soil moisture
content-pressure head curve. The particular form of the equation enables one to derive closed-form
analytical expressions for the relative hydraulic conductivity, when substituted in the predictive conductivity
models of Burdine or Mualem. The resulting expressions for the hydraulic conductivity as function of the
pressure head contain three independent parameters which may be obtained by fitting the described soil
moisture retention model to experimental soil moisture retention data. The solution is based on automatic
curve-fitting using a nonlinear least squares method.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications)
Documentation includes: model theory, user's instructions
Availability: public domain
Remarks:
This model is available from the International Ground Water Modeling Center, Colorado School of
Mines, Golden, CO 80401.
References:
Van Genuchten, M.Th. 1978. Calculating the Unsaturated Hydraulic Conductivity with a New
Closed-form Analytical Model. 78-WR-08, Water Resources Program, Princeton University,
Princeton, New Jersey.
IGWMC Key: 5183 Model Name: SOILPROP
Authors: Mishra, S., J.C. Parker, and N. Singhal
Institution of Model Development: Environmental Systems & Technologies, Inc.
Blacksburg, Virginia
Code Custodian: J.C. Parker
Environmental Systems & Technologies, Inc.
P.O. Box 10547, Blacksburg, VA 24062-0457
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Abstract:
SOILPROP is an interactive program to estimate soil hydraulic properties and their uncertainty from particle
size distribution data. Properties estimated by the program are the saturated hydraulic conductivity and
parameters in the van Genuchten and Brooks-Corey models which describe the relationship between soil
water content, capillary pressure and relative permeability. SOILPROP is based on the premise that the
soil-water retention function reflects a pore size distribution which in turn can be inferred from the grain size
distribution. The Arya-Paris procedure is used to compute theoretical water content versus capillary
pressure curve, which is then fitted to the two models. Covariances are estimated using a first-order error
analysis procedure.
Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications), demonstration/education
Documentation includes: model theory, user's instructions, example problems, verification/validation
Verification/validation: verification (analyt.solutions)
Peer (independent) review: concepts, theory (math)
Availability: proprietary, license
Remarks:
The saturated hydraulic conductivity in SOILPROP is estimated from the user-specified porosity and
grain-size distribution data using a Kozeny-Carmen type equation.
References:
Arya, L.M., and J.F. Paris. 1981. A Physico-Empirical Model to Predict Soil Moisture Characteristics
from Particle Size Distribution and Bulk Density Data. Soil Sci. Soc. Amer. Journ., Vol. 45, pp.
1023-1030.
Mishra, S.J., J.C. Parker, and N. Singhal. 1989. Estimation of Soil Hydraulic Properties and their
Uncertainty from Particle Size Distribution Data. Journ. of Hydrology, Vol. 108, pp. 1-18.
Mishra, S., and J.C. Parker. 1989. Effects of Parameter Uncertainty on Prediction of Unsaturated
Flow. Journ. of Hydrology, Vol. 108, pp. 19-33.
IGWMC Key: 5187 Model Name: FLOFIT
Authors: Kool, J.B., S. Mishra, and J.C. Parker
Institution of Model Development: Environmental Systems & Technologies, Inc., Blacksburg, Virginia
Code Custodian: J.C. Parker
Environmental Systems & Technologies, Inc.
P.O. Box 10457, Blacksburg, VA 24062-0457
Abstract:
FLOFIT is a program to estimate unsaturated soil hydraulic properties and/or transport parameters from
1 -dimensional vertical flow/transport experiments. Three modes of operation are possible: 1) flow properties
may be estimated from transient flow data; 2) solute dispersion and linear adsorption parameters may be
estimated from steady flow transport data; or 3) flow and transport parameters may be estimated
simultaneousiy from transient unsaturated flow and tracer experiments. Hydraulic properties are described
by a hysteric van Genuchten model and dispersion by a scale-dependent function. Hydraulic and/or
transport parameters may differ between layers. Numerical inversion of governing equations is performed
using an efficient Levensberg-Marquardt algorithm.
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Model developed for: research (e.g. hypothesis/theory testing), general use (e.g. in field
applications)
Documentation includes: user's instructions
Availability: proprietary, license
IGWMC Key: 6228 Model Name: RETC (Retention Curve Computer Code)
Authors: Van Genuchten, M.Th., F.J. Leij, and S.R. Yates
Institution of Model Development: USDA Salinity Lab., Riverside, California
Code Custodian: M.Th. van Genuchten
U.S. Dept. of Agriculture, U.S. Salinity Lab., Agric. Res. Service, 4500 Glenwood
Drive, Riverside, Calif. 92501
Abstract:
RETC uses theoretical methods to predict the soil water retention curve and the hydraulic conductivity curve
from measured soil water retention data. It uses several analytical models to estimate water retention,
unsaturated hydraulic conductivity or soil water diffusivity for a given soil. It includes the parametric
equations of Brooks-Corey and van Genuchten, which are used in conjunction with the theoretical pore-size
distribution models of Mualem and Burdine to predict unsaturated hydraulic conductivity from observed soil
water retention data. RTC can be used in a forward mode and in a parameter fitting mode. In the forward
mode it estimates the soil-water retention curve and hydraulic conductivity; in the parameter fitting mode
it determines the analytical model parameters.
Model developed for: general use (e.g. in field applications), demonstration/education
Documentation includes: model theory, user's instructions, example problems, program structure
and development, code listing, verification/validation
Verification/validation: verification (analyt.solutions), laboratory data sets, field datasets (validation)
Peer (independent) review: concepts, theory (math), documentation
Availability: public domain
Remarks:
This software is available from the Center for Subsurface Modeling Support (CSMOS), R.S. Kerr
Environmental Research Laboratory, U.S. Environmental Protection Agency, P.O. Box 1198, Ada,
OK 74820
References:
van Genuchten, M.Th., F.J. Leij and S.R. Yates. 1991. The RETC Code for Quantifying the
Hydraulic Functions of Unsaturated Soils. EPA/600/2-91/065, U.S. Environm. Protection Agency,
R.S. Kerr Environm. Res. Lab., Ada, Oklahoma.
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Appendix 8: List of Input Requirements for Selected Unsaturated Zone Models
RITZ
Fractional organic carbon content
Soil bulk density
Saturated water content of soil
Saturated hydraulic conductivity
Clapp and Hornberger constant
Concentration of pollutant in sludge
Organic carbon partition coefficient
Oil-water partition coefficient
Henry's law constant
Diffusion constant of pollutant in air
Half life of pollutant
Concentration of oil in sludge
Density of oil
Half life of oil
Sludge application rate
Plow zone depth
Treatment zone depth
Recharge rate
Evaporation rate
Air temperature
Relative humidity
Diffusion coefficient of water vapor in air
FLAME
Control
Type of transport simulation (time-varying
or steady-state)
Characteristics of boundary value
problem (uniform or non-uniform
initial condition; specified
boundary conditions; point
sources)
Computational solution procedures (band
or frontal solver; linear or
quadratic finite element shape
functions)
Coordinate system to be used (cartesian
or radial; vertical, horizontal or
planar)
Output print control (echo all; minimum
echo; full echo)
File input control (files for mesh, initial
conditions, soil properties, head,
velocity, restart, and/or) results
Planes for which mass flux across is to
be calculated
Time integration factor
Minimum change in concentration
Maximum change in concentration
Grid scale factor in x- and y-direction
Time dependent data (number of
subintervals; output time plane
for each subinterval)
Nodal and element data
Grid information (element number,
corresponding node numbers,
element material number,
element ordering index; node
number, x-coordinate and z-
coordinate)
Initial conditions (location and value)
Boundary conditions (location type and
value: fixed concentration for 1st
type; time of application/duration
and mass source rate for 2nd
type)
Material data
Element data (material number,
longitudinal and transverse
dispersivity, saturated hydraulic
conductivity in x- and z-direction,
saturated moisture content or
porosity, line element width,
retardation factor, half-life,
molecular diffusion coefficient,
tortuosity in x- and z-direction)
Characteristic and relative hydraulic
conductivity curve data (tabular
data including pressure heads,
volumetric moisture content,
relative hydraulic conductivity)
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FLASH
Control
Processes to be modelled (heat
transport, unsaturated flow,
Dupuit-Forcheimer flow,
horizontal flow)
Type of simulation (time-varying or
steady-state)
Characteristics of boundary value
problem (uniform or non-uniform
initial condition; specified
boundary conditions, constant or
time-varying flux, or mixed
boundary condition)
Computational solution procedures
(Picard or Newton iteration; band
or frontal solver; linear or
quadratic finite element shape
functions)
Coordinate system to be used (cartesian
or radial; vertical, horizontal or
planar)
Output print control (echo all; minimum
echo; full echo)
File input control (files for mesh, initial
conditions, soil properties, head,
velocity, restart, and/or) results
Planes for which mass flux across is to
be calculated
Time integration factor
Relative error criteria
Maximum change in pressure head
Maximum change in temperature
Grid scale factor in x- and y-direction
Time dependent data (number of
subintervals; output time plane
for each subinterval)
Nodal and element data
Grid information (element number,
corresponding node numbers,
element material number,
element ordering index; node
number, x-coordinate and z-
coordinate)
Initial conditions (location and value for
pressure head or temperature)
Boundary conditions (location type and
value: transient fixed pressure
head for unsaturated flow or total
head for saturated flow for 1st
type; transient volumetric heat or
fluid flux for 2nd type)
Material data
Element data (material number,
volumetric heat capacity, thermal
conductivity, specific storage,
saturated conductivity in x- and
z-direction, saturated moisture
content or porosity, line element
width)
Characteristic and relative hydraulic
conductivity curve data (tabular
data including pressure heads,
volumetric moisture content,
relative hydraulic conductivity)
Relationship of thermal conductivity and
moisture content or pressure
head (tabular data)
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MULTIMED
Unsaturated zone
Saturated hydraulic conductivity
Unsaturated zone porosity
Air entry pressure head
Depth of unsaturated zone
Number of nodal points residual water content
Number of porous materials
Number of layers
Alfa coefficient
Van Genuchten exponent
Thickness of each layer
Longitudinal dispersivity of each layer
Percent organic matter
Bulk density of soil for each layer
Biological decay coefficient for unsaturated zone
Acid catalyzed hydrolysis rate
Neutral hydrolysis rate constant
Base catalyzed hydrolysis rate
Reference temperature
Normalized distribution coefficient
Air diffusion coefficient
Reference temperature for air diffusion
Molecular weight
Infiltration rate
Area of waste disposal unit
Duration of pulse
Source decay constant
Initial concentration at landfill
Particle diameter
Saturated zone
Recharge rate
Overall 1st order decay for saturated zone
Biodegradation coefficient for saturated zone
Aquifer thickness
Hydraulic gradient
Longitudinal dispersivity
Transverse dispersivity
Vertical dispersivity
Temperature of aquifer
pH
Organic carbon content
Well distance from site
Angle off center
Well vertical distance
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VS2DT
Variable
Definition
DXl(NN)
DX2(NN)
DZl(NN)
DZ2(NN)
VX(NN)
VZ(NN)
CC(NN)
COLD(NN)
CS(NN)
QT(NN)
NCTYP(NN)
RET(NN)
ANG
TRANS
TRANS1
SSTATE
CIS
CIT
EPS1
VPNT
SORP
XX Component of hydrodynamic dispersion tensor at left side
of cell times Ax/Az, L2T~1.
XZ Component of hydrodynamic dispersion tensor at left side
of cell times Ax/2Az, L2T~1.
ZZ Component of hydrodynamic dispersion tensor at top of cell
times Az/Ax, L2T~1.
ZX Component of hydrodynamic dispersion tensor at top of cell
times Az/2Ax, L2T~1.
X Velocity at left side of cell, LT"1.
Z Velocity at top of cell, LT'1.
Concentration, ML"3.
Concentration at previous time step, ML"3.
Concentration of specified fluid sources, ML"3.
Fluid flux through constant head nodes, L3T-1.
Boundary condition or cell type indicator:
0 = internal node,
1 = specified concentration node, and
2 = specified solute flux node.
Slope of adsorption isotherm times bulk density,
dimensionless.
Angle at which grid is to be tilted, degrees.
If = T, solute transport and flow are to be simulated; if = F,
only flow is simulated.
If = T, matrix solver solves for head; if = F, matrix solver
solves for concentration.
If = T, steady-state flow has been achieved.
If = T, centered-in-space differencing is used for transport
equation; if = F, backward-in-space differencing is used.
If = T, centered-in-time differencing is used for transport
equation; if = F, backward-in-time differencing is used.
Convergence criteria for transport equation, ML"3.
If = T, velocities are written to file 6.
If = T, nonlinear sorption is to be simulated.
Note: NN = number of nodes
A-8-4
-------
VS2DT (continued)
Card Variable Description
[Line group A read by VSEXEC]
A-l TITL 80-character problem description
(formatted read, 20A4).
A-2 TMAX Maximum simulation time, T.
STIM Initial time (usually set to 0), T.
ANG Angle by which grid is to be tilted
(Must be between -90 and +90
degrees, ANG = 0 for no tilting, see
Supplemental.Information for further
discussion), degrees.
A-3 ZUNIT Units used for length (A4).
TUNIT Units used for time (A4).
CUNX Units used for mass (A4).
Note: Line A-3 is read in 3A4 format, so the unit designations must occur
in columns 1-4, 5-8, 9-12, respectively.
A-4 NXR Number of cells in horizontal or
radial direction.
NLY Number of cells in vertical direction.
A-5 NRECH Number of recharge periods.
NUMT Maximum number of time steps.
A-6 RAD Logical variable = T if radial
coordinates are used; otherwise = F.
ITSTOP Logical variable = T if simulation is
to terminate after ITMAX iterations
in one time step; otherwise = F.
TRANS Logical variable = T if solute
transport is to be simulated.
Line A-6A is present only if TRANS = T.
A-6A CIS Logical variable = T if centered-in-
space differencing is to be used; = F
if backward-in-space differencing
is to be Used for transport
equation.
CIT Logical variable = T if centered-in-
time differencing is to be used; = F
if backward-in-time or fully
implicit differencing is to be used.
SORP Logical variable = T if nonlinear
sorption or ion exchange is to be
simulated. Nonlinear sorption
occurs when ion exchange, Langmuir
isotherms, or Freundlich isotherms
with n not equal to 1 are used.
A-7 F11P Logical variable = T if head, moisture
content, and saturation at selected
observation points are to be written
to file 11 at end of each time step;
otherwise = F.
A-8-5
-------
VS2DT (continued)
Card
Variable
Description
A-?--Continued F7P
F8P
F9P
F6P
A-8
A-9
THPT
SPNT
PPNT
HPNT
VPNT
IFAC
Logical variable = T if head changes
for each iteration in every time
step are to be written in file 7;
otherwise = F.
Logical variable = T if output of
pressure heads (and concentrations
if TRANS = T) to file 8 is desired
at selected observation times;
otherwise = F.
Logical variable = T if one-line mass
balance summary for each time step
to be written to file 9; otherwise
= F.
Logical variable = T if mass balance
is to be written to file 6 for each
time step; = F if mass balance is to
be written to file 6 only at
observation times and ends of
recharge periods.
Logical variable = T if volumetric
moisture contents are to be written
to file 6; otherwise = F.
Logical variable = T if saturations
are to be written to file 6;
otherwise = F.
Logical variable = T if pressure heads
are to be written to file 6;
otherwise = F.
Logical variable = T if total heads
are to be written to file 6;
otherwise = F.
Logical variable ~ T if velocities are
to be written to file 6; requires
TRANS = T.
= 0 if grid spacing in horizontal (or
radial) direction is to be read in
for each column and multiplied by
FACX.
= 1 if all horizontal grid spacing is
to be constant and equal to FACX.
= 2 if horizontal grid spacing is
variable, with spacing for the first
two columns equal to FACX and the
spacing for each subsequent column
equal to XMULT times the spacing of
the previous column, until the
spacing equals XMAX, whereupon
spacing becomes constant at XMAX.
A-8-6
-------
VS2DT (continued)
2™* Variable Description
A-9—Continued FACX Constant grid spacing in horizontal
(or radial) direction (if IFAC=1);
constant multiplier for all spacing
(if IFAC=0); or initial spacing (if
IFAC=2), L.
Line set A-10 is present if IFAC = 0 or 2.
If IFAC = 0,
A-10 DXR Grid spacing in horizontal or radial
direction. Number of entries must
equal NXR, L.
If IFAC = 2,
A-10 XMULT Multiplier by which the width of each
node is increased from that of the
previous node.
XMAX Maximum allowed horizontal or radial
spacing, L.
A-11 JFAC = 0 if grid spacing in vertical
direction is to be read in for each
row and multiplied by FACZ.
= 1 if all vertical grid spacing is to
be constant and equal to FACZ.
= 2 if vertical grid spacing is
variable, with spacing for the first
two rows equal to FACZ and the
spacing for each subsequent row
equal to ZMULT times the spacing at
the previous row, until spacing
equals ZMAX, whereupon spacing
becomes constant at ZMAX.
FACZ Constant grid spacing in vertical
direction (if JFAC=1); constant
multiplier for all spacing (if JFAC
=0); or initial vertical spacing (if
JFAC=2), L.
Line set A-12 is present only if JFAC = 0 or 2.
If JFAC = 0,
A-12 DELZ Grid spacing in vertical direction;
number of entries must equal NLY, L.
If JFAC = 2,
A-12 ZMULT Multiplier by which each node is
increased from that of previous node.
ZMAX Maximum allowed vertical spacing, L.
Line sets A-13 to A-14 are present only if F8P = T,
A-13 NPLT Number of time steps to write heads and
concentrations to file 8 and heads,
concentrations, saturations, and/or
moisture contents to file 6.
A-8-7
-------
VS2DT (continued)
Card
Variable
Description
A-14
PLTIM
Elapsed times at which pressure heads
and concentrations are to be written
to file 8, and heads, concentrations,
saturations, and/or moisture contents
to file 6, T.
Line sets A-15 to A-16 are present only if F11P = T,
A-15 NOBS Number of observation points for which
heads, concentrations, moisture
contents, and saturations are to be
written to file 11.
A-16 J,N Row and column of observation points.
A double entry is required for each
observation point, resulting in
2xNOBS values.
Lines A-17 and A-18 are present only if F9P = T.
A-17 NMB9 Total number of mass balance
components to be written to File 9.
A-18 MB9 The index number of each mass balance
component to be written to file 9.
(See table 7 in Supplemental
Information for index key)
[Line group B read by subroutine VSREAD]
B-l
EPS
HMAX
WUS
B-3
B-4
EPS1
MINIT
ITMAX
PHRD
Closure criteria for iterative solution
of flow equation, units used for head,
L.
Relaxation parameter for iterative
solution. See discussion in Lappala
and others (1987) for more detail.
Value is generally in the range of 0.4
to 1.2.
Weighting option for intercell relative
hydraulic conductivity: WUS = 1 for
full upstream weighting. WUS = 0.5 for
arithmetic mean. WUS =0.0 for
geometric mean.
Closure criteria for iterative solution
of transport equation, units used for
concentration, ML"3. Present only if
TRANS = T.
Minimum number of iterations per time
step.
Maximum number of iterations per time
step. Must be less than 200.
Logical variable = T if initial
conditions are read in as pressure
heads; = F if initial conditions
are read in as moisture contents.
A-8-8
-------
VS2DT (continued)
Card Variable Description
B-5 NTEX Number of textural classes or
lithologies having different values
of hydraulic conductivity, specific
storage, and/or constants in the
functional relations among pressure
head, relative conductivity, and
moisture content.
NPROP Number of flow properties to be read
in for each textural class. When
using Brooks and Corey or van
Genuchten functions, set NPROP = 6,
and when using H^verkamp functions,
set NPROP = 8. When using tabulated
data, set NPROP = 6 plus number of
data points in table. [For example,
if the number of pressure heads in
the table is equal to Nl, then set
NPROP =3*(N1+1)+3]
NPROP1 Number of transport properties to be
read in for each textural class.
For no adsorption set NPROP1 = 6.
For a Langmuir or Freundlich isotherm
set NPROP1 = 7. For ion exchange set
NPROP1 = 8. Present only if TRANS =
T.
Line sets B-6, B-7, and B-7A must be repeated NTEX times
B-6 ITEX Index to textural class.
B-7 ANIZ(ITEX) Ratio of hydraulic conductivity in the
z-coordinate direction to that in the
x-coordinate direction for textural
class ITEX.
HK(ITEX,1) Saturated hydraulic conductivity (K) in
the x-coordinate direction for class
ITEX, LT'1.
HK(ITEX,2) Specific storage (S ) for class ITEX,
IT1. S
HK(ITEX,3) Porosity for class ITEX.
Definitions for the remaining sequential values on this line are dependent
upon which functional relation is selected to represent the nonlinear
coefficients. Four different functional relations are allowed: (1) Brooks
and Corey, (2) van Genuchten, (3) Haverkamp, and (4) tabular data. The
choice of which of these to use is made when the computer program is
compiled, by including only the function subroutine which pertains to the
desired relation (see discussion in Lappala and others (1987) for more
detail).
A-8-9
-------
VS2DT (continued)
Card
Variable
Description
B-7--Continued
In the following descriptions, definitions for the different functional
relations are indexed by the above numbers. For tabular data, all
pressure heads are input first (in decreasing order from the largest to the
smallest), all relative hydraulic conductivities are then input in the same
order, followed by all moisture contents.
HK(ITEX,4)
HK(ITEX,5)
(1) h., L. (must be less than 0.0).
(2) a', L. (must be less than 0.0).
(3) A', L. (must be less than 0.0).
(4) Largest pressure head in table.
(1) Residual moisture content (6 ).
(2) Residual moisture content (6 ).
(3) Residual moisture content (9 ).
(4) Second largest pressure head in table.
(1) X, pore-size distribution index.
(2) P1.
(3) B1.
(4) Third largest pressure head in table.
(1) Not used.
(2) Not used.
(3) a, L. (must be less than 0.0).
(4) Fourth largest pressure head in table.
(1) Not used.
(2) Not used.
(3) p.
(4) Fifth largest pressure head in table.
For functional relations (1), (2), and (3) no further values are required
on this line for this textural class. For tabular data (4), data input
continues as follows:
HK(ITEX,6)
HK(ITEX,7)
HK(ITEX,8)
HK(ITEX,9)
K(ITEX,Nl+3)
HK(ITEX,Nl+4)
HK(ITEX,Nl+5)
HK(ITEX,Nl+6)
Next largest pressure head in table.
Minimum pressure head in table.
(Here Nl = Number of pressure heads in table; NPROP
Always input a value of 99.
Relative hydraulic conductivity corresponding to first
pressure head.
Relative hydraulic conductivity corresponding to second
pressure head.
HK(ITEX,2*Nl+4)
HK(ITEX,2*Nl+5)
HK(ITEX,2*Nl+6)
Relative hydraulic conductivity corresponding to smallest
pressure head.
Always input a value of 99.
Moisture content corresponding to first pressure head.
A-8-10
-------
VS2DT (continued)
Card Variable Description
B-7--Continued
HK(ITEX,2*Nl+7) Moisture content corresponding to second pressure head.
HK(ITEX,3*Nl+5) Moisture content corresponding to smallest pressure head.
HK(ITEX,3*Nl+6) Always input a value of 99.
Regardless of which functional relation is selected there must be NPROP+1
values on line B-7.
Line B-7A is present only if TRANS = T.
B-7A HT(ITEX.l) OL> L.
HT(ITEX,2) OT, L.
HT(ITEX,3) Dm, L2!'1.
HT(ITEX,4) X, decay constant, T'1.
HT(ITEX,5) p. (can be set to 0 for no adsorption
or ion exchange), ML"3.
HT(ITEX,6) = 0 for no adsorption or ion exchange,
= K, for linear adsorption isotherm,
= KI for Langmuir isotherm,
= Kf for Freundlich isotherm,
= K for ion exchange.
m
HT(ITEX,7) = Q for Langmuir isotherm,
= n for Freundlich isotherm (Note: n
is a real, rather than an integer,
variable),
= Q for ion exchange, not used when
adsorption is not simulated.
HT(JTEX,8) = C0 for ion exchange, only used for
ion exchanged.
B-8 IROW If IROW = 0, textural classes are read
for each row. This option is
preferable if many rows differ from
the others. IF IROW = 1, textural
classes are read in by blocks of
rows, each block consisting of all
the rows in sequence consisting of
uniform properties or uniform
properties separated by a vertical
interface.
Line set B-9 is present only if IROW = 0.
B-9 JTEX Indices (ITEX) for textural class for
each node, read in row by row. There
must be NLY*NXR entries.
A-8-11
-------
VS2DT (continued)
Card
Variable
Description
Line set B-10 is present only if IROW = 1.
As many groups of B-10 variables as are needed to completely cover the
grid are required. The final group of variables for this set must have
IR = NXR and JBT = NIY.
B-10
IL
IR
JBT
JRD
Left hand column for which texture
class applies. Must equal 1 or
[IR(from previous card)+l].
Right hand column for which texture
class applies. Final IR for sequence
of rows must equal NXR.
Bottom row of all rows for which the
column designations apply. JBT must
not be increased from its initial or
previous value until IR = NXR.
Texture class within block.
Note: As an example, for a column of uniform material; IL = 1, IR = NXR,
JBT = NLY, and JRD = texture class designation for the column material.
One line will represent the set for this example.
B-ll
IREAD
If IREAD = 0, all initial conditions
in terms of pressure head or moisture
content as determined by the value of
PHRD are set equal to FACTOR. If
IREAD = 1, all initial conditions are
read from file IU in user-designated
format and multiplied by FACTOR. If
IREAD = 2 initial conditions are
defined in terms of pressure head, and
an equilibrium profile is specified
above a free-water surface at a depth
of DWTX until a pressure head of HMIN
is reached. All pressure heads above
this are set to HMIN.
Multiplier or constant value, depending
on value of IREAD, for initial
conditions, L.
Line B-12 is present only if IREAD = 2,
B-12 DWTX Depth to free-water surface above which
an equilibrium profile is computed, L.
HMIN Minimum pressure head to limit height
of equilibrium profile; must be less
than zero, L.
FACTOR
A-8-12
-------
VS2DT (continued)
Card Variable Description
Line B-13 is read only if IREAD = 1,
B-13 IU Unit number from which initial head
values are to be read.
IFMT Format to be used in reading initial
head values from unit IU. Must be
enclosed in quotation marks, for
example '(10X.E10.3)'.
B-14 BCIT Logical variable = T if evaporation is
to be simulated at any time during
the simulation; otherwise = F.
ETSIM Logical variable = T if
evapotranspiration (plant-root
extraction) is to be simulated at any
time during the simulation; otherwise
= F.
Line B-15 is present only if BCIT = T or ETSIM = T.
B-15 NPV Number of ET periods to be simulated.
NPV values for each variable required
for the evaporation and/or
evapotranspiration options must be
entered on the following lines. If
ET variables are to be held constant
throughout the simulation code,
NPV = 1.
ETCYC Length of each ET period, T.
Note: For example, if a yearly cycle of ET is desired and monthly values of
PEV, PET, and the other required ET variables are available, then code NPV
= 12 and ETCYC = 30 days. Then, 12 values must be entered for PEV, SRES, HA,
PET, RTDPTH, RTBOT, RTTOP, and HROOT. Actual values, used in the program,
for each variable are determined by linear interpolation based on time.
Line B-16 to B-18 are present only if BCIT = T.
B-16 PEVAL Potential evaporation rate (PEV) at
beginning of each ET period. Number
of entries must equal NPV, LT-1.
To conform with the sign convention used in most existing equations for
potential evaporation, all entries must be greater than or equal to 0. The
program multiplies all nonzero entries by -1 so that the evaporative flux is
treated as a sink rather than a source.
A-8-13
-------
VS2DT (continued)
Card Variable Description
B-17 RDC(l.J) Surface resistance to evaporation (SRES)
at beginning of ET period, L"1. For a
uniform soil, SRES is equal to the
reciprocal of the distance from the
top active node to land surface, or
2./DELZ(2). If a surface crust is
present, SRES may be decreased to
account for the added resistance to
water movement through the crust.
Number of entries must equal NPV.
B-18 RDC(2,J) Pressure potential of the atmosphere
(HA) at beginning of ET period; may
be estimated using equation 6 of
Lappala and others (1987), L. Number
of entries must equal NPV.
Lines B-19 to B-23 are present only if ETSIM = T.
B-19 PTVAL Potential evapotranspiration rate (PET)
at beginning of each ET period, LT"1.
Number of entries must equal NPV. As
with PEV, all values must be greater
than or equal to 0.
B-20 RDC(3,J) Rooting depth at beginning of each ET
period, L. Number of entries must
equal NPV.
B-21 RDC(4,J) Root activity at base of root zone at
beginning of each ET period, L~2.
Number of entries must equal NPV.
B-22 RDC(5,J) Root activity at top of root zone at
beginning of each ET period, IT2.
Number of entries must equal NPV.
Note: Values for root activity generally are determined empirically, but
typically range from 0 to 3.0 cm/cm3. As programmed, root activity
varies linearly from land surface to the base of the root zone, and its
distribution with depth at any time is represented by a trapezoid. In
general, root activities will be greater at land surface than at the
base of the root zone.
B-23 RDC(6,J) Pressure head in roots (HROOT) at
beginning of each ET period, L.
Number of entries must equal NPV.
Lines B-24 and B-25 are present only if TRANS = T.
B-24 IREAD If IREAD = 0, all initial concentrations
are set equal to FACTOR. If IREAD
= 1, all initial concentrations are
read from file IU in user designated
format and multiplied by FACTOR.
A-8-14
-------
VS2DT (continued)
Card
Variable
Description
B-24--Continued FACTOR
Multiplier or constant value, depending
on value of IREAD, for initial
concentrations.
1.
Unit number from which initial
concentrations are to be read.
Format to be used in reading initial
head values from unit IU. Must be
enclosed in quotation marks, for
example '(10X, E10.3)1.
[Line group C read by subroutine VSTMER, NRECH sets of C lines are required]
Line B-25 is present only if IREAD
B-25 IU
IFMT
C-l
C-2
TPER
DELT
TMLT
DLTMX
DLTMIN
TRED
C-3
DSMAX
STERR
C-4
C-5
POND
PRNT
C-6
BCIT
Length of this recharge period, T.
Length of initial time step for this
period, T.
Multiplier for time step length.
Maximum allowed length of time step, T.
Minimum allowed length of time step, T.
Factor by which time-step length is
reduced if convergence is not obtained
in ITMAX iterations. Values usually
should be in the range 0.1 to 0.5. If
no reduction of time-step length is
desired, input a value of 0.0.
Maximum allowed change in head per time
step for this period, L.
Steady-state head criterion; when the
maximum change in head between
successive time steps is less than
STERR, the program assumes that steady
state has been reached for this period
and advances to next recharge period,
L.
Maximum allowed height of ponded water
for constant flux nodes. See Lappala
ans others (1987) for detailed
discussion of POND, L.
Logical variable = T if heads,
concentration, moisture contents,
and/or saturations are to be printed
to file 6 after each time step; = F if
they are to be written to file 6 only
at observation times and ends of
recharge periods.
Logical variable = T if evaporation is
to be simulated for this recharge
period; otherwise = F.
A-8-15
-------
VS2DT (continued)
Description
C-6--Continued ETSIM Logical variable = T if
evapotranspiration (plant-root
extraction) is to be simulated for
this recharge period; otherwise = F.
SEEP Logical variable = T if seepage faces
are to be simulated for this recharge
period; otherwise = F
C-7 to C-9 cards are present only if SEEP = T,
C-7 MFCS Number of possible seepage faces. Must
be less than or equal to 4.
Line sets C-8 and C-9 must be reported NFCS times
C-8 JJ Number of nodes on the possible seepage
face.
JLAST Number of the node which initially
represents the highest node of the
seep; value can range from 0 (bottom
of the face) up to JJ (top of the
face).
C-9 J,N Row and column of each cell on possible
seepage face, in order from the lowest
to the highest elevation; JJ pairs of
values are required.
C-10 IBC Code for reading in boundary conditions
by individual node (IBC=0) or by row
or column (IBC=1). Only one code may
be used for each recharge period, and
all boundary conditions for period
must be input in the sequence for
that code.
Line set C-ll is read only if IBC = 0. One line should be present for each
node for which new boundary conditions are specified.
C-ll JJ Row number of node.
NN Column number of node.
NTX Node type identifier for boundary
conditions.
= 0 for no specified boundary (needed
for resetting some nodes after
intial recharge period);
= 1 for specified pressure head;
= 2 for specified flux per unit
horizontal surface area in units of
LT-1;
= 3 for possible seepage face;
= 4 for specified total head;
= 5 for evaporation;
= 6 for specified volumetric flow in
units of L3T-1.
A-8-16
-------
VS2DT (continued)
Card Variable Description
Oil—Continued PFDUM Specified head for NTX = 1 or 4 or
specified flux for NTX = 2 or 6. If
codes 0, 3, or 5 are specified, the
line should contain a dummy value for
PFDUM or should be terminated after
NTX by a blank and a slash.
NTC Node type identifier for transport
boundary conditions
= 0 for no specified boundary;
= 1 for specified concentration, ML~3;
= 2 for specified mass flux, MT'1.
Present only if TRANS = T.
CF Specified concentration for NTC = 1 or
NTX = 1,2,4, or 6; or specified flux
for NTC = 2. Present only if TRANS
= T.
C-12 is present only if IBC = 1. One card should be present for each row or
column for which new boundary conditions are specified,
C-12 JJT Top node of row or column of nodes
sharing same boundary condition.
JJB Bottom node of row or column of nodes
having same boundary condition. Will
equal JJT if a boundary row is being
read.
NNL Left column in row or column of nodes
having same boundary condition.
NNR Right column of row or column of nodes
having same boundary condition. Will
equal NNL if a boundary column is
being read in.
NTX Same as line C-ll.
PFDUM Same as line C-ll.
NTC Same as line C-ll.
CF Same as line C-ll.
C-13 Designated end of recharge period. Must be included after
line C-12 data for each recharge period. Two C-13 lines
must be included after final recharge period. Line must
always be entered as 999999 /.
A-8-17
-------
Appendix 9: Checklist for MARS Annotation
MODEL IDENTIFICATION
Model Name
IGWMC Key
Date of First Release
Current Version Number
Current Version Release Date
Authors
Institution of Model Development
Code Custodian (contact person, address)
IGWMC Check Date
COMPUTER AND SOFTWARE SPECIFICATION
Computer systems for which versions exist
(supercomputer, minicomputer, work-
stations, mainframe, microcomputer)
System requirements (RAM for execution, mass
storage for programs and I/O files;
numerical/math coprocessor, compiler
required for main frame, MS Windows,
other resident software
Graphics requirements (graphic board/monitor
type/mode, resident graphic drivers)
Optional capabilities (plotter, printer, mouse)
Program information (programming language/
level, number of program statements, size
of source code, size of runtime/compiled
version)
IGWMC
Primary Development Objective (research, e.g.
hypothesis/theory testing; general use,
e.g. in field applications; demonstration/
education)
Documentation (model theory, user's instructions,
input preparation, model set-up, model
options, example problems, demonstra-
tion of input/output illustrative of model
options, program structure, program
design/development, code listing,
verification, validation)
Availability
Terms (public domain, restricted public
domain, proprietary, purchase,
license)
Form (source code only, compiled code
only, source and compiled code,
paper listing of source code
Simulation Input Preparation or Preprocessing
(textual data entry/editing, graphic data
entry/modification, automatic grid
generation, data reformatting, error-
checking, help screens)
Data postprocessing (textual screen display, data
storage in ASCII file, data directly to
printer, graphic screen display of spatial
data, graphic screen display of temporal
data, direct graphic plotting, data
reformatting
EVALUATION
Code Use: few (<10); moderate (10-25);
many (> 25)
Verification/validation (verific. with analyt.
solutions, verific. with synthetic datasets,
testing with field datasets, testing with
laboratory datasets, code inter-
comparison)
Performance testing (stability, efficiency)
Peer (independent) review (concepts, theory,
coding, accuracy, documentation,
usability, efficiency)
Support
Can be used without support
Level of available support (full, limited,
none, support agreement
available)
A-9-1
-------
GENERAL MODEL CAPABILITIES
Units (metric, S.I., U.S.)
Parameter discretization (lumped, water/mass
balance model, response function model,
distributed, stochastic)
Spatial orientation
saturated flow
1D -horizontal
-vertical
2D -horizontal (areal)
-vertical (crossectional/profile)
-axi-symmetric
3D -fully-3D (definition in x,y,z)
-quasi-3D (layered; Dupuit
approximation)
-cylindrical or radial
Grid Design
Grid discretization applicable
-constant cell size
-variable grid size
-movable grid (relocation of
nodes during run)
-automatic grid generation
-maximum # of nodes
Coupling (equations coupled, model modules
coupled, internal software linkage,
external I/O linkage)
unsaturated flow
1D -horizontal
-vertical
2D -horizontal
-vertical
-axi-symmetric
3D -fully-3D
-cylindrical or radial
Possible cell shapes
1D -linear
-curvilinear
2D -triangular
-curved triangular
-square
-rectangular
-quadrilateral
-curved quadrilateral
-polygon
3D -cubic
-hexahedral
-tetrahedral
-cylindrical
-spherical
REMARKS
REFERENCES
USERS
A-9-2
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Partlla. Fluid Flow Models
FLOW SYSTEM CHARACTERIZATION
Saturated zone
Hydrogeologic zoning (single aquifer, single
aquifer/aquitard system, multiple
aquifer/aquitard systems)
Aquifer type(s) present (confined, semi-confined
or leaky confined, unconfined or phreatic)
Hydrogeologic medium (porous media, fractured
media, discrete fractures, equivalent
fracture approach, equivalent porous
media approach, stochastic approach,
dual porosity system or flow in fractures
and porous blocks)
Row characteristics (laminar flow Darcian flow,
laminar non-Darcian flow, turbulent flow,
steady-state, transient)
Flow parameter representation (homogeneous or
heterogeneous, isotropic or anisotropic)
Well representation (partial penetration, filter
dimensions, wellbore storage, skin
effects)
Changing aquifer conditions in space (variable
thickness, confined to unconfined or
reverse, pinching aquifer, pinching
aquitard)
Changing aquifer conditions in time (desaturation,
confined/unconfined, resaturation of dry
cells, parameter values)
Processes (area! recharge from surface, induced
recharge from stream, aquitard storage,
delayed yield from storage, freezing/
thawing, vaporization/condensation,
evaporation, evapotranspiration
Unsaturated Zone
Medium (porous media, layered porous media,
aerially homogeneous or single soil type,
aerially heterogeneous or multi soil types,
macropores present, fractured media,
dual porosity system, perched water
table, dipping soil layers)
Flow characteristics (laminar Darcian flow,
laminar non-Darcian flow, turbulent flow,
steady-state, transient)
Processes: -infiltration(fixed head, fixed flux,
ponding, infiltration
function)
-evaporation
-evapotranspiration
-plant uptake of water
-capillary rise
-hysteresis
-interflow
-swelling/shrinking soil matrix
Parameter definition (K^,, suction vs. saturation,
porosity, residual saturation, hydraulic
conductivity vs. saturation, number of soil
materials possible)
Soil moisture saturation - matric potential
relationship (Brutsaert 1966, van
Genuchten 1980, Haverkamp et al. 1977,
tabular)
Soil hydraulic conductivity-saturation/hydraulic
potential relationship (Wind 1955, Brooks
and Corey 1966, van Genuchten 1980,
Gardner 1958, Haverkamp et al. 1977,
Averjanov 1950, Rijtema 1965, tabular)
Parameter representation (homogeneous,
heterogeneous, isotropic, anisotropic)
Intercell conductance representation or K,
determination (arithmetic, harmonic,
geometric)
A-9-3
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FLUID CONDITIONS
Single fluid flow (water, vapor/gas/air, or
nonaqueous-phase liquids)
Fluid properties (compressible fluid, spatially
variable fluid density, temporally variable
fluid density, density-temperature relation-
ship, density-concentration relationship,
variable viscosity)
Row of multiple fluids (water and air/vapor, water
and steam, salt-water and fresh-water
with a sharp interface and either stagnant
salt-water or moving salt-water and
moving fresh-water, water and NAPL with
about equal densities, water and DNAPL,
water and LNAPL, liquid NAPL and
gaseous NAPL)
BOUNDARY AND INITIAL CONDITIONS FOR FLOW
First type - Dirichlet:
-head/pressure (constant in time, varying
in time, cyclic functions)
-prescribed moisture content (either
constant in time or time-varying)
Second type - Neumann (either constant in time
or time-varying):
- injection/production wells
- areal recharge in the saturated zone
- areal infiltration in the unsaturated zone
- no-flow
- cross-boundary flow
Third type - Cauchy:
- head-dependent flux (either constant in
time or time-varying)
-free surface (either constant in time or
time-varying)
-seepage face (either constant in time or
time-varying)
-springs
-induced infiltration (from surface water)
-ponding
Initial Conditions (saturation, moisture content,
suction, total hydraulic head, hydraulic
potential)
SOLUTION METHODS - FLOW MODELS
General Method:
Water balance approach
Analytical (single solution, superposition,
method of images, analytical
element method)
Semi-analytical (continuous in time and
discrete in space, continuous in
space and discrete in time,
approximate analytical solution)
Matrix-solving technique/Iterative (SIP,
Gauss-Seidel or PSOR, LSOR, BSOR,
Iterative ADIP or IADI, Predictor-
corrector)
Matrix-solving technique/Semi-iterative
(conjugate-gradient)
Numerical/spatial approximation (block-centered
finite difference, node-centered finite
difference, integrated finite difference,
boundary element method, particle
tracking, pathline integration, Galerkin
finite element method, point collocation
method, subdomain collocation method)
Numerical/time-stepping scheme (fully implicit,
fully explicit, Crank-Nicholson)
Matrix-solving technique/Direct (Gauss
elimination, Cholesky decomposition,
Frontal method, Doolittle, Thomas
algorithm, Point Jacobi
Iterative methods for nonlinear equations (Picard
method, Newton-Raphson method, Chord
slope method)
A-9-4
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INVERSE/PARAMETER IDENTIFICATION FOR FLOW
Parameters to be identified (hydraulic
conductivity, transmissivlty, storativity/
storage coefficient, leakeance/leakage
factor, areal recharge, cross-boundary
fluxes, pumping rates, soil parameters/
coefficients)
User input (prior information on variable to be
determined, constraints on variable to be
determined, instability conditions, non-
uniqueness criteria, regularity conditions,
aquifer properties, soil properties)
Parameter identification method/Direct method
i.e. model parameters treated as
dependent variable (energy dissipation
method, algebraic approach, inductive
method or direct integration of PDE,
minimizing norm of error flow or flatness
criterion, linear programming, quadratic
programming, matrix inversion)
Parameter identification method/Indirect method
i.e. iterative improvement of parameter
estimates (quasi-linearization, linear
programming, quadratic programming,
steepest descent, conjugate gradient,
non-linear regression or Gauss-Newton
method, Newton-Raphson, influence
coefficient, maximum likelihood, co-
kriging, gradient search, decomposition
and multi-level optimization, least-
squares)
OUTPUT CHARACTERISTICS - FLOW MODELS
Echo of input (nodal coordinates, cell size,
element connectivity, initial heads/
pressures/potentials initial moisture
content/saturation, soil parameters/
function coefficients, aquifer parameters,
boundary conditions, stresses such as
recharge and pumping)
Type of output:
-head/pressure/potential (tables,
contours, time series graphs)
-saturation/moisture content (tables,
contours, time series graphs)
-head differential/drawdown (tables,
contours, time series graphs)
-internal (cross-cell) fluxes (tables, vector
plots, time series graphs)
-infiltration fluxes (tables, vector plots,
time series graphs)
-evapo(transpi) ration fluxes (tables,
vector plots, time series graphs)
Form of output (binary file, ASCII file with text,
x-y[-z]/f{x,y,z} file, t/f{t} file, direct
screen display, direct hardcopy on
printer, direct plot on pen-plotter, graphic
file)
-cross boundary fluxes (tables, vector
plots, time series graphs)
-velocities (tables, vector plots, time
series graphs)
-stream function values (tables, contours)
-streamlines/pathlines (graphics)
-traveltimes (tables)
-isochrones (graphics)
-position of interface (tables, graphics)
-location of seepage faces
-water budget components (cell-by-cell
or global)
-calculated parameters
A-9-5
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Part lib. Solute Transport Models
WATER QUALITY CONSTITUENTS
Any constituent(s) vs. specific constituents (total
dissolved solids, heavy metals, other
metals, nitrates and nitrogen compounds,
phosphates and phosphorus compounds,
sulfates and sulphur compounds,
chlorides, aromatic organic compounds,
oxygenated organic compounds,
halogenated organic compounds, micro-
organisms, radionuclides)
Single vs. multi-species transport (single
constituent, two constituents, multiple
constituents)
PROCESSES
Conservative transport (uniform or non-uniform
steady-state or transient advection,
dispersion, molecular diffusion, plant
solute uptake)
Phase transfers (solid<->gas or vapor sorption;
solid <-> liquid or liquid sorption including
equilibrium isotherms such as linear,
Langmuir, Freundlich, or non-equilibrium
isotherms; desorption i.e. hysteresis;
liquid->gasorvolatilization;liquid->solids
or filtration)
Parameter representation:
-dispersivity (isotropic i.e.
homogeneous i.e.
heterogeneous)
-diffusion coefficient (homogeneous,
geneous)
-retardation factor (homogeneous, hetero-
geneous)
aT=aL, anisotropic,
constant in space,
hetero-
Fate:
-Type of reactions (ion exchange, substitution/
hydrolysis, dissolution/precipitation,
reduction/oxidation, acid/base reactions,
complexation, aerobic or anaerobic
biodegradation)
-Form of reactions (zero order production/decay,
first order production/decay, chemical
production/decay, radioactive decay
including single mother/daughter decay
and chain decay, microbial production/
decay with Monod functions for aerobic
biodegradation or Michaelis-Menten
function for anaerobic biodegradation)
Chemical processes embedded in transport
equation or given by separate equation(s)
BOUNDARY CONDITIONS FOR SOLUTE TRANSPORT
First type - Dirichlet: concentration (constant in
time, varying in time, at domain
boundary, at injection wells if flow rate is
given)
Second type - Neumann: prescribed solute flux
(constant in time or time-varying, point
sources e.g. injection wells, line sources
e.g. infiltration ditches, area! sources e.g.
feedlots and landfills, non-point or diffuse
sources)
SOLUTION METHODS - SOLUTE TRANSPORT MODELS
Flow and solute transport equations are uncoupled or coupled (through concentration-dependent density
or viscosity).
A-9-6
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SOLUTION METHODS - SOLUTE TRANSPORT MODELS (continued)
General Method:
-Solute mass balance approach, analytical (single
solution, superposition), semi-analytical
(continuous in time and discrete in space,
continuous in space and discrete in time,
approximate analytical solution)
Numerical/time-stepping scheme (fully implicit,
fully explicit, Crank-Nicholson)
Matrix-solving technique/Iterative (SIP,
Gauss-Seidel or PSOR, LSOR, BSOR,
Iterative ADIP or I ADI, Predictor-
corrector)
Matrix-solving technique/Semi-iterative
(conjugate-gradient)
Numerical/spatial approximation (block-centered
finite difference, node-centered finite
difference, integrated finite difference,
boundary element method, particle
tracking, method of characteristics,
random walk method, Galerkin finite
element method, point collocation
method, subdomain collocation method)
Matrix-solving technique/Direct (Gauss
elimination, Cholesky decomposition,
Frontal method, Doolittle, Thomas
algorithm, Point Jacob!
Iterative methods for nonlinear equations (Picard
method, Newton-Raphson method, Chord
slope method)
INVERSE/PARAMETER IDENTIFICATION FOR SOLUTE TRANSPORT
Parameters to be identified (velocity, dispersivity,
diffusion coefficient, retardation factor,
source strength, initial conditions in terms
of concentrations)
Parameter identification method/Direct method
i.e. model parameters treated as
dependent variable (energy dissipation
method, algebraic approach, inductive
method or direct integration of PDE,
minimizing norm of error flow or flatness
criterion, linear programming, quadratic
programming, matrix inversion)
User input (prior information, constraints,
instability conditions, non-uniqueness
criteria, regularity conditions)
Parameter identification method/Indirect method
i.e. iterative improvement of parameter
estimates (linear or quadratic
programming, steepest descent,
conjugate gradient, non-linear regression,
Newton-Raphson, influence coefficient,
maximum likelihood, co-kriging, gradient
search, least-squares)
OUTPUT CHARACTERISTICS - SOLUTE TRANSPORT MODELS
Echo of input (initial concentrations, parameter
values, boundary conditions, stresses i.e.
source fluxes)
Type of output:
-concentration values (tables, contours,
time series graphs)
-concentration in pumping wells (time
series tables and graphs)
-calculated parameters
Form of output (binary file, ASCII file with text,
x-y[-2]/f{x,y,z} file, t/f{t} file, direct
screen display, direct hardcopy on
printer, direct plot on pen-plotter, graphic
file)
-internal and cross-boundary solute
fluxes (tables, vector plots, time
series graphs)
-velocities (from given heads)
-mass balance components (cell-by-cell
or global)
A-9-7
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Part lie. Heat Transport Models
PROCESSES
Transport processes (uniform or non-uniform Internal heat generation (internal heat source)
steady-state or transient convection, Parameter representation (parameters not
conduction through rock-matrix, mentioned are considered homogeneous
conduction through liquid, thermal in space):
dispersion, thermal diffusion between -thermal conductivity of rock matrix
rock matrix and liquid, radiation) (homogeneous, heterogeneous)
Phase change (evaporation and condensation, -thermal dispersion coefficient (isotropic
water and vapors, water and steam, i.e. aT=aL, anisotropic, homo-
freezing and thawing, heat exchange geneous i.e. constant in space,
between phases) heterogeneous)
BOUNDARY CONDITIONS FOR HEAT TRANSPORT
First type - Dirichlet: temperature (constant in Second type - Neumann: heat flux (constant in
time or time-varying source at domain time or time-varying release at point
boundary or at injection wells) sources, line sources, area! sources, or
Third type - Cauchy: given geothermal gradient non-point diffuse sources)
SOLUTION METHODS - HEAT TRANSPORT MODELS
Flow and heat transport equations are uncoupled or coupled (through temperature-dependent density or
viscosity).
General Method: Heat or energy balance Numerical/spatial approximation (block-centered
approach, analytical (single solution, finite difference, node-centered finite
superposition), semi-analytical difference, integrated finite difference,
(continuous in time and discrete in space, boundary element method, particle
continuous in space and discrete in time, tracking, method of characteristics,
approximate analytical solution) random walk method, Galerkin finite
element method, point collocation
Numerical/time-stepping scheme (fully implicit, method, subdomain collocation method)
fully explicit, Crank-Nicholson)
Matrix-solving technique/Iterative (SIP, Matrix-solving technique/Direct (Gauss
Gauss-Seidel or PSOR, LSOR, BSOR, elimination, Cholesky decomposition,
Iterative ADIP or IADI, Predictor- Frontal method, Doolittle, Thomas
corrector) algorithm, Point Jacobi
Matrix-solving technique/Semi-iterative Iterative methods for nonlinear equations (Picard
(conjugate-gradient) method, Newton-Raphson method, Chord
slope method)
OUTPUT CHARACTERISTICS - HEAT TRANSPORT MODELS
Echo of input (initial temperatures, parameter Form of output (binary file, ASCII file with text,
values, boundary conditions, stresses i.e. x-y[-z]/f{x,y,z} file, t/f{t} file, direct
source fluxes) screen display, direct hardcopy on
printer, direct plot on pen-plotter, graphic
file)
A-9-8
-------
OUTPUT CHARACTERISTICS - HEAT TRANSPORT MODELS (continued)
Type of output:
-temperature values (tables, contours, -internal and cross-boundary heat fluxes
time series graphs) (tables, vector plots, time series
-temperature in pumping wells (time graphs)
series tables and graphs) -velocities (from given heads)
-calculated parameters -heat/energy balance components
-frost front location (tables, graphs) (cell-by-cell or global)
A-9-9
Tj-U.S. GOVERNMENT PRINTING OFFICE. 1994 - 550-001/80356
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