GROUND WATER -- Release of OFR 94-59, "Documentation of a Computer Program to Simulate Transient Leakage from Confining Units Using the Modular Finite-Difference Ground-Water Flow Model" by S.A. Leake, P. Patrick Leahy, and Anthony S. Navoy




In Reply Refer To:                          July 12, 1994
Mail Stop 411



OFFICE OF GROUND WATER TECHNICAL MEMORANDUM 94.04


Subject:  GROUND WATER -- Release of OFR 94-59, "Documentation
          of a Computer Program to Simulate Transient Leakage
          from Confining Units Using the Modular Finite-
          Difference Ground-Water Flow Model" by S.A. Leake,
          P. Patrick Leahy, and Anthony S. Navoy

The subject report describes the addition of a Transient Leakage
(TLK) Package to the U.S. Geological Survey modular model,
MODFLOW.  The TLK Package simulates transient leakage into or
out of a compressible, fine-grained confining unit as a result
of ground-water storage changes.  The TLK Package works by
solving equations defining the flow across the confining unit
boundaries.  The method generally requires considerably less
computational effort and computer memory than using multiple
model layers to simulate the confining unit.  We recommend that
this report be brought to the attention of technical and
management personnel concerned with ground-water modeling
studies.

A version of MODFLOW has been created that incorporates the TLK
Package along with most of the other published MODFLOW
additions.  The Hydrologic Analysis Support Section (HASS) is
handling the distribution of this program within the Water
Resources Division.  HASS recently sent an electronic mail
message to all system administrators describing how to retrieve
and install a compiled version of this program for use on Data
General computers.  To determine if the updated version of
MODFLOW has been installed on your computer, issue the following
command:

    what /usr/opt/bin/modflow

Several lines of information should appear on your computer
display, and one of these lines should state that the version
is 2.4.  If this version of MODFLOW has not been installed on
your computer, contact your system administrator.  If there are
problems installing the software or if you would like the source
code for the program, contact HASS by electronic mail (wrdapp)
or by phone (Steve Regan 703-648-5896).

Additional copies of the report are available from Stan Leake in
the Arizona District.

                                      Sincerely,




                                      /s/ William M. Alley
                                      Chief, Office of
                                      Ground Water

Distribution:  A and B (memo only)
               S, FO, and PO (memo and report)