NAME
modpath - A particle-tracking postprocessor model for
MODFLOW
SYNOPSIS
mpath3 [i] [filename]
mplot3 [i] [filename]
ABSTRACT
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.
OPTIONS
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.
METHOD
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.
HISTORY
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 REQUIREMENTS
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 OPTIONS
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.
SYSTEM REQUIREMENTS
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.
APPLICATIONS
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.
DOCUMENTATION
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.
RELATED DOCUMENTATION
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
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.
CONTACTS
Operation:
U.S. Geological Survey
Office of Ground Water
David Pollock
411 National Center
Reston, VA 20192
dwpolloc@usgs.gov
Distribution:
U.S. Geological Survey
Hydrologic Analysis Software Support Program
437 National Center
Reston, VA 20192
h2osoft@usgs.gov
Official versions of U.S. Geological Survey water-resources
analysis software are available for electronic retrieval via
the World Wide Web (WWW) at:
http://water.usgs.gov/software/
and via anonymous File Transfer Protocol (FTP) from:
water.usgs.gov (path: /pub/software).
The WWW page and anonymous FTP directory from which the
MODPATH software can be retrieved are, respectively:
http://water.usgs.gov/software/modpath.html
--and--
/pub/software/ground_water/modpath
See
http://water.usgs.gov/software/ordering_documentation.html
for information on ordering printed copies of USGS
publications.
SEE ALSO
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
model