GROUND WATER -- Simulation of contaminant movement UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY RESTON VIRGINIA 22092 Code 4351 5016 February 8, 1978 GROUND WATER BRANCH TECHNICAL MEMORANDUM NO. 79.05 SUBJECT: GROUND WATER -- Simulation of contaminant movement Because the contamination of a ground-water resource is a serious problem that may have long-term economic, social, and physical consequences, methods are needed to predict the effects of man's activities on ground-water quality. Reliable predictions of contaminant movement can only be made if we understand the processes controlling the convective transport, hydrodynamic dispersion, and chemical reactions affecting the concentration of dissolved chemicals in ground water, and if we can quantitatively represent them in a systematic model. Aquifers generally have heterogeneous properties and irregular boundary conditions; therefore, the solution of the mathematical equations that describe the transport processes generally requires the use of deterministic, distributed parameter, digital simulation models. The enclosed report, "Computer model of two-dimensional solute transport and dispersion in ground water," by L. F. Konikow and J.D. Bredehoeft, is a comprehensive documentation of one such model. The model represents a valuable tool that can be used in the analysis of ground-water quality changes. Its capability for computing the movement of dissolved chemicals in flowing ground water can help in (1) understanding the causes of observed concentration patterns, (2) estimating future changes in chemical concentration with time and space, (3) planning and designing projects to minimize ground-water contamination, (4) estimating the time of travel between a source of contamination and a ground- water discharge or observation point, such as a stream, spring, or well, (5) designing an effective and efficient monitoring system, and (6) evaluating the physical and economic feasibility of alternative reclamation plans for removing contaminants from an aquifer or preventing contaminants from spreading. The report was released as Techniques of Water-Resources Investigations, Book 7, Chapter C2. The program is general and flexible in that it can be readily and directly applied to a wide variety of field problems. However, in some cases it may have to be modified by the user for efficient application to his specific field problem. The numerical procedure uses a finite-difference approximation to solve the ground-water flow equation and the method of characteristics to solve the solute-transport equation. The model assumes that the solute is nonreactive and that differences in fluid density, viscosity, and temperature do not affect fluid velocity. The program is written in FORTRAN IV, and the report includes a program listing. The source deck and compiled program are available on the IBM and Honeywell MULTICS (Reston and Denver) systems. On the IBM, a load module (program number K590) is available using SYS1.LOADLIB on either RE1 or RE2. Following is a sample JCL sequence to execute this program: // JOB (...) // EXEC FORTRUN,PROG=K590,REGION.GO=190K,TIME.GO=2 //GO.SYSIN DD * On the Honeywell, segments moc.fortran, which is the source code, and moc, which is the object code, are accessible in directory >udd>Transport>LKonikow. Additional instructions for retrieval or use can be obtained from the Ground Water Branch. The data requirements, input format specifications, program options, and output formats are all structured in a general manner that should be readily adaptable to many field problems. The report includes input and output examples from a sample problem. (s) Leonard F. Konikow (for) Chief, Ground Water Branch Attachment WRD Distribution: A, B, S, FO