PERSONNEL--Training: Ground-Water Flow Modeling Courses UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY RESTON, VA. 22092 In Reply Refer To: March 10, 1982 Mail Stop 411 GROUND WATER BRANCH TECHNICAL MEMORANDUM NO. 82.04 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 handled. 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 simulation. (s) Gordon D. Bennett Chief, Ground Water Branch WRD Distribution: A, B, S, FO, PO