PERSONNEL--Training: Ground-Water Flow Modeling Courses

                        GEOLOGICAL SURVEY
                        RESTON, VA. 22092

In Reply Refer To:                            March 10, 1982
Mail Stop 411


Subject:  PERSONNEL--Training: Ground-Water Flow Modeling Courses

A new finite difference ground-water flow model is presently being
developed by Michael McDonald of the Ground Water Branch and Arlen
Harbaugh of the New Jersey District.  The model is designed to
simulate flow in three dimensions; two-dimensional areal problems
may be handled as single-layer cases, and two-dimensional cross-
section problems as single-column or single-row cases.

The program is broken into independent packages, each of which is
designed to accomplish a particular task.  Thus an alternate
version of any individual package can be developed and inserted
without requiring changes to computer code in other packages.
This is in contrast to the existing flow models in use in the
Division, which may require modifications in many sections of the
code in order to change the approach to an individual feature of
the simulation, such as the way in which evapotranspiration is

We believe the modular approach of the new model will allow
improvement in technology to be introduced and documented in an
orderly fashion, as they are developed, and will eliminate much of
the confusion which has characterized the development of the
models now in use.  It is our hope that the new model will become
a standard tool for finite difference simulation in field projects
and will gradually replace the finite difference codes now
supported by the Branch.  However, we will continue to provide
support for the existing two-dimensional and three-dimensional
models for a reasonable period of time.

In the past, simulation of ground-water flow has been presented in
two short courses at the Training Center.  The basic course
presented general finite difference theory, and experience with
the two-dimensional flow model; approximately 1 week of the
advanced course was devoted to the three-dimensional model.
Obviously, the training courses will have to be redesigned as the
new model is introduced.  We are currently working on this
problem, as well as on the more general problem of finding
supplements and alternatives to the short course approach.  During
the remainder of this fiscal year, however, two sessions of the
Advanced Modeling course are scheduled.  We plan to use the first
of these, May 5-14, 1982, to present the new finite difference
model.  The second course, September 13-24, 1982, will be used to
present theory and practice in two-dimensional finite element flow

                                   (s) Gordon D. Bennett
                                   Chief, Ground Water Branch

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