Water Resources Applications Software

Geochemical || Ground Water || Surface Water || Water Quality || General

Summary of MODPATH

     modpath - A particle-tracking postprocessor model for

     mpath3 [i] [filename]

     mplot3 [i] [filename]

     MODPATH is a particle-tracking postprocessing package that
     was developed to compute three-dimensional flow paths using
     output from steady-state or transient ground-water flow
     simulations by MODFLOW, the U.S. Geological Survey finite-
     difference ground-water flow model.  The particle tracking
     package consists of two Fortran computer codes: (1) MODPATH,
     which calculates particle paths, and (2) MODPATH-PLOT, which
     displays results graphically.

     i          Tells the program to prompt for all input
                interactively.  A "response file" is produced
                which records user responses for the execution of
                the program.

     filename   The name of an existing "response file."

     If no option is given, the program will prompt for the name
     of a "response file".  If none is given, the program will
     proceed in the interactive mode.  Response files can be made
     to include interactive prompts by adding the string "(?)" to
     the end of the last line of a prompt message.  This is
     useful, for example, when plots are needed for multiple
     reference times with all other responses the same.

     MODPATH uses a semi-analytical particle tracking scheme that
     allows an analytical expression of the particle's flow path
     to be obtained within each finite-difference grid cell.
     Particle paths are computed by tracking particles from one
     cell to the next until the particle reaches a boundary, an
     internal sink/source, or satisfies some other termination
     criterion.  Both steady-state and transient ground-water
     flow systems can be analyzed with MODPATH.

     Version 3.2 2000/06/14 - Dynamic memory allocation added to
        allow for very large problems and minimize the need for
        source-code recompilation.  Additional graphical output
        options provided in precompiled MODPATH-PLOT.  Fixed
        problem causing MODPATH to fail when trying to read the
        MODFLOW head file for cases where the MODFLOW-96 XSECTION
        option was used to save the heads as a single 2D cross
        section.  Fixed problem causing end-of-file error when
        reading the cell-by-cell budget file when list-oriented
        stress packages (e.g. rivers, drains, etc.) had zero
        entries for one or more stress periods.  Fixed bug
        causing the automatic particle generation option to fail
        for transient simulations where the number of columns was
        larger than the number of rows.

     1994 - version 3 released (no version 2 was released)

     1989 - version 1 released

     Data input for MODPATH and MODPATH-PLOT is a combination of
     data files and interactive keyboard input.  Keyboard input
     also can be redirected to a data file.  Both programs are
     designed to work with MODFLOW.  The number of new data files
     required by MODPATH is minimized by making use of MODFLOW
     data files whenever possible.

     Output from MODPATH is in the form of a variety of numerical
     data files containing spatial coordinates of particles and
     traveltime.  Output from MODPATH-PLOT is primarily
     graphical.  The graphical output is dependent on the
     capabilities of the GKS graphics system installed on the
     computer system.

     MODPATH and MODPATH-PLOT are written primarily in standard
     Fortran 77; a few Fortran 90 statements have been added for
     dynamic array allocation.  The code can be compiled with any
     standard Fortran 90 compiler.  The code can also be compiled
     using a standard Fortran 77 compiler when alternate Fortran
     77 statements for static array dimensioning are uncommented.
     In addition to a Fortran compiler, MODPATH-PLOT requires a
     graphics subroutine library known as GKS (Graphical Kernel
     System).  GKS is a standardized set of graphics routines
     that are available commercially for most computer systems.
     The code has been used on UNIX-based computers and on DOS-
     and Windows-based computers.

     The MODPATH package has been widely applied to MODFLOW-based
     ground-water flow simulation studies.  It is useful as a
     visualization tool to help understand flow patterns in
     simulated ground-water flow systems.  It also has been
     widely used to delineate sources of water to discharge sites
     and aquifers in systems simulated with MODFLOW.
     Pollock, D.W., 1994, User's Guide for MODPATH/MODPATH-PLOT,
        Version 3: A particle tracking post-processing package
        for MODFLOW, the U.S. Geological Survey finite-difference
        ground-water flow model: U.S. Geological Survey Open-File
        Report 94-464, 234 p.

     Pollock, D.W., 1994, Source Code and Ancillary Data Files
        for the MODPATH Particle Tracking Package of the Ground-
        Water Flow Model MODFLOW -- Version 3, Release 1: U.S.
        Geological Survey Open-File Report 94-463, 2 p., two
        3.5-inch diskettes.

     Training in the use of MODPATH is included in the USGS
     MODFLOW training courses Modeling of Ground-Water Flow Using
     Finite-Difference Methods (GW2096TC) and Advanced Finite-
     Difference Modeling of Ground-Water Flow (GW3099TC), offered
     annually at the USGS National Training Center.

           U.S. Geological Survey
           Office of Ground Water
           David Pollock
           411 National Center
           Reston, VA 20192


           U.S. Geological Survey
           Hydrologic Analysis Software Support Program
           437 National Center
           Reston, VA 20192


     Official versions of U.S. Geological Survey water-resources
     analysis software are available for electronic retrieval via
     the World Wide Web (WWW) at:


     and via anonymous File Transfer Protocol (FTP) from:

       (path: /pub/software).

     The WWW page and anonymous FTP directory from which the
     MODPATH software can be retrieved are, respectively:


     for information on ordering printed copies of USGS

     contour(1) - A contouring program for gridded data

     modflow(1) - Modular three-dimensional finite-difference
                  ground-water flow model

     Modflowp(1) - Parameter-estimation version of the modular

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