Techniques of Water-Resource Investigations (TWRI) Report, Book 6, Chapter A1, "A Modular Three-Dimensional Finite-difference Ground-Water Flow Model,"

In Reply Refer To:                                 June 17, 1988
WGS-Mail Stop 411


Subject:  PUBLICATIONS--Techniques of Water-Resources
                        Investigations (TWRI) Report, Book 6,
                        Chapter A1, "A Modular Three-Dimensional
                        Finite-Difference Ground-Water Flow
                        Model," by M. G. McDonald and A. W.

The subject report replaces Open-File Report 83-875.  The new
report is similar to the old one, but many sections of the text
have been modified to add more detailed explanations.  Also, a
number of changes were made to the model program, but it functions
just as the previous version did.  Most of the program changes
were made for the purpose of converting it to FORTRAN 77.  This
version should be even more portable than the original FORTRAN 66
version.  For example, it runs on IBM Personal Computers under
Microsoft FORTRAN without any modification.  Datasets used with
the original version of the program should produce identical
results when used with the new version.

The new report may be ordered from the Books and Open-File Reports
Section at the Denver Federal Center by submitting Form 9-1986.
There is no charge if ordered for official use by USGS employees
however, if more than four copies are being ordered, Form 9-1986
must be sent through Kathleen Iseri in Reston. The cost to the
public is $27.

Water-Resources Division employees may obtain the new version of
the model program in several ways:

1.  Use the Software Exchange (SoftEx) on the QVARSB Prime
    computer to obtain the program as a single file.  The SoftEx
    entry number is VAKJH00011.

2.  Issue the following command from your own Prime computer to
    obtain the program as a single file:


where "xxx" is the pathname for the program on your computer.

3.  Send electronic mail to Mike McDonald or Arlen Harbaugh (EDOC
identifiers are given below) requesting the program.  You will
receive the program in multiple files (one file per model
package), sample problem input data, and compilation instructions.
Include in the request the name of the directory that you want the
files sent to.

The program that is sent by any of the above methods has two
changes from what is published in the new TWRI report.  It has the
BAS Package input unit set to 5 (rather than 1) as is usual on
Prime computers, and the X array is dimensioned to 350000 rather
than 30000.

Please report any problems with the new report or program to Mike
McDonald (FTS 959-5805, EDOC user identifier MGMCDONALD) or Arlen
Harbaugh (FTS 959-5615, EDOC user identifier AHARBAUGH).

                                         Eugene P. Patten
                                         Chief, Office of
                                         Ground Water

WRD Distribution:  A, B, S, FO, PO