1. General Model Information

Name: Variably Saturated 2-D Flow and Transport Model

Acronym: VS2DT

Main medium: terrestrial
Main subject: biogeochemistry, hydrology
Organization level: ecosystem
Type of model: partial differential equations (finite differences,2D), ordinary differential equations
Main application:
Keywords: soil, unsaturated, saturated, flow, solute transport, variably saturated porous media, evaporation, transpiration , ion exchange, 2D , nonuniform soil, richards equation, convection-dispersion equation, finite difference numerics, sink terms, nonlinear adsorption isotherms


U.S. Geological Survey
Hydrologic Analysis Software Support Team
R. Steven Regan
437 National Center
Reston, VA 20192
email: h2osoft@usgs.gov


R.W. Healy (U.S. Geological Survey)


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 root 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.

The IGWMC preprocessor PREVS2DT facilitates data entry by prompting the user for VS2D/T input parameters. The IGWMC post-processor POSTVS rewrites VS2D/T output into a form suitable for contouring with a commercial contouring package. All three programs in the package (PreVS2DT, VS2D/T, and (POSTVS) are run from a menu system (VSHELL).

II. Technical Information

II.1 Executables:

Operating System(s): The International Groud Water Modeling Center distributes VS2D/T Version 2.0 (1992) program package including Pre- and Postprocessor and comprehensive documentation.for around US$ 250.- Version 2.4, compiled for UNIX - systems is available free directly from the USGS:
USGS VS2DT for DG/Sun systems - Version: 2.4 last updated 1996/04/09 and their european mirror site :
USGS VS2DT for DG/Sun systems - Version: 2.4 last updated 1996/04/09 An older version of VS2D/T (Version date 4-1-1990) compiled for DOS including the source-code and an input file example is available from Richard B. Winstons ftp directory DOS (inclusive source)

II.2 Source-code:

Programming Language(s): FORTRAN

II.3 Manuals:

The reports (see References) can be obtained from US Geological Survey, WRD National Water Information System 437 National Center 12201 Sunrise Valley Drive Reston, Virginia 22092 Phone: (703)648-6978 or Books and Open-File Reports Section U.S. Geological Survey Federal Center, Box 25425 Denver, Colorado 80225 Phone: (303)236-7476

II.4 Data:

III. Mathematical Information

III.1 Mathematics

III.2 Quantities

III.2.1 Input

III.2.2 Output

IV. References

The program VS2DT is documented in US Geological Survey WRI 83-4099 and 90-4025. Complete citations are
Lappala, E.G., Healy, R.W., and Weeks, E.P. 1983. Documentation of computer program VS2D to solve the equations of fluid flow in variably saturated porous media. US Geological Survey Water-Resources Investigations Report 83-4099.
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.
Healy, R.W., 1987, Simulation of trickle irrigation, an extension to the U.S. Geological Survey's Computer Program VS2D: U.S. Geological Survey Water-Resources Investigations Report 87-4086, 61 p.
VS2DT is being used by personnel in several districts, as well as by scientists at various universities and consulting companies. An application is described in:
Mills, P.C., and Healy, R.W., 1993, Water and tritium movement through the unsaturated zone at a low-level radioactive-waste disposal site near Sheffield, Illinois, 1981-85: U.S. Geological Survey Water-Supply Paper 2386, 72 p.

V. Further information in the World-Wide-Web

VI. Additional remarks

Last review of this document by: T. Gabele: 17. 07. 1997 -
Status of the document:
last modified by Tobias Gabele Wed Aug 21 21:44:52 CEST 2002

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