UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY RESTON, VIRGINIA 22092 GW Branch December 29, 1977 Code: 4060 0001 Memorandum GROUND WATER BRANCH TECHNICAL MEMORANDUM NO. 78.03 Subject: PUBLICATIONS--Report, "Derivation of equations describing solute transport in ground water," by Leonard F. Konikow and David B. Grove, WRI 77-19 Increased attention in recent years to problems of ground-water contamination has stimulated the development of methods useful to the understanding and quantitative description of the physical and chemical processes that control the transport of solutes in ground water. The principal interest in these methodologies is the ability to predict the rate and directions of movement of contaminants from either existing or potential sources. A solute transport model requires the solution of both the equation describing flow and the equation describing the transport and dispersion of reacting dissolved chemicals in a ground-water system. Because of the complexity of real-world aquifer systems, the solution of these equations requires the use of numerical approximating techniques. Solute-transport models utilized at present in WRD employ either finite-difference methods, finite- element methods, the method of characteristics, or some combination of these methods. The selection of the "best" model to use is largely problem-dependent. Familiarity with and understanding of the equations is basic to the use of any solute transport model. The enclosed report by Konikow and Grove gives a detailed, step-by-step derivation of a general form of the solute transport equation. The report shows how the general equation can be modified or simplified for application to a variety of field problems. The derivation is presented in a manner intended to stress understanding, more so than mathematical rigor, of the reasoning and/or assumptions leading to each step. Although other derivations of the transport equation are in the published literature, we believe that the manner of development of this derivation makes it a good introduction to quantitative modeling of solute-transport processes in ground water. Limited additional copies of the report are available on request to the Ground Water Branch. (s) Charles A. Appel (for) Chief, Ground Water Branch Enclosure WRD Distribution: A(memo only), B-Limited(w/encl.), FO-LS (w/encl.)PUBLICATIONS--Report, "Derivation of equations describing solute transport in ground water,"