Techniques and Methods 6–A41
![]() ABSTRACTMODPATH is a particle-tracking post-processing model that computes three-dimensional flow paths using output from groundwater flow simulations based on MODFLOW, the U.S. Geological Survey (USGS) finite-difference groundwater flow model. This report documents MODPATH version 6. Previous versions were documented in USGS Open-File Reports 89–381 and 94–464. The program uses a semianalytical particle-tracking scheme that allows an analytical expression of a particle's flow path to be obtained within each finite-difference grid cell. A particle's path is computed by tracking the particle from one cell to the next until it reaches a boundary, an internal sink/source, or satisfies another termination criterion. Data input to MODPATH consists of a combination of MODFLOW input data files, MODFLOW head and flow output files, and other input files specific to MODPATH. Output from MODPATH consists of several output files, including a number of particle coordinate output files intended to serve as input data for other programs that process, analyze, and display the results in various ways. MODPATH is written in FORTRAN and can be compiled by any FORTRAN compiler that fully supports FORTRAN-2003 or by most commercially available FORTRAN-95 compilers that support the major FORTRAN-2003 language extensions. |
First posted June 14, 2012
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Pollock, D.W., 2012, User guide for MODPATH version 6—A particle-tracking model for MODFLOW: U.S. Geological Survey Techniques and Methods, book 6, chap. A41, 58 p.
Abstract
Introduction
Method
Semianalytical Tracking Algorithm
Special Cases
Backward Tracking
Transient Flow
Solute Retardation
Limitations
MODPATH Overview
Time Concepts
Flow Boundaries
Terminating Particles
Model Input
Model Output
Program Portability and Compatibility
Input Instructions
General Structure of Input Data
Simulation File
Basic Data File
Name File
Starting Locations File
Particle Output File Structure
Endpoint File
Pathline File
Timeseries File
Advective Observations File
Example Problem
References
Appendix 1. MODPATH Output Examiner