|WORLD METEOROLOGICAL ORGANIZATION||
|Explanation of the criteria for classification and numbering of components|| L20.2.04
|Explanation of the dates on the component's description|
MODULAR FINITE-DIFFERENCE GROUNDWATER FLOW MODEL (MODFLOW)
1. Purpose and objectives
The MODFLOW model simulates groundwater flow in a porous medium in
three dimensions. It is designed for use by experienced groundwater hydrologists. A modular structure was used for the program and
documentation in order to make the model easy to understand and easy to
modify when necessary.
Aquifer hydraulic parameters, boundary conditions, initial conditions,
and stresses are required model input. The input is from text files with
the data laid out in a prescribed order and format. The input data must
correspond to the specified grid structure. Many MODFLOW users make use of
separate programs to help discretize the data and lay them out in the
required form. However, no such support programs are included as part of
The primary model output is the head at each model node. In addition a water budget is calculated, and the flow through each model cell can be
stored in a disk file. As is the case with input, support programs are
often used to analyze and display the output, though again these are not
included in MODFLOW.
5. Operational requirements and restrictions
MODFLOW is written in the FORTRAN 77 language. It can run on a wide range of computers from personal computers to super computers. A math coprocessor is strongly recommended for' performance reasons. It should be
noted that some FORTRAN compilers require a math coprocessor. The computational time and memory requirements depend on the size of the problem being simulated.
6. Form of presentation
The source code in FORTRAN 77 is supplied on a 3 1/2" floppy diskette or via the Internet, together with the MODFLOW documentation report in
English (see reference).
7. Operational experience
MODFLOW, which is probably the most widely used groundwater model in the world, today, has been used extensively inside and outside of the U.S. Geological Survey since 1983.
8. Originator and technical support
U.S. Geological Survey, Office of Ground Water.
From the HOMS National Reference Centre for USA for 3 1/2" floppy or printed documentation; or electronically on the Internet at
10. Conditions on use
Program and electronic version of the documentation are available free of charge; there is a charge for printed documentation.
McDonald, M. G. and Harbaugh, A. W., 1988, A modular three-dimensional finite-difference groundwater flow model: U.S. Geological Survey, Techniques of Water Resources Investigations, Book 6, Chapter Al, 586 pp.
|(First entered: 01 FEB 93||
Last updated: 28 MAR 94)