BALANCE is a program designed to define and quantify chemical equilibrium reactions between ground-water and minerals. Using (1) the chemical compositions of water samples from two points along a flow path and (2) a set of mineral phases hypothesized to be the reactive constituents in the system, the program calculates the mass transfer (amounts of the phases entering or leaving the aqueous phase) necessary to account for the observed changes in composition between the two water samples. Additional constraints can be included in the problem formulation to account for mixing of two end-member waters, redox reactions, and, in a simplified form, isotopic composition.

BALANCE runs as a batch program requiring input files prepared with the preprocessor BALNINPT, or a text editor. The preprocessor automatically accesses a chemical reaction data base, BALNINPT.DAT, included with the software.

BALANCE, a public domain program, is distributed on a 3½" DOS-formatted disk containing source code and runtime versions. The documentation includes a description of the underlying principles and the input necessary to run the program, and three examples typical of ground-water systems. Note: BALANCE is no longer maintained by the developers; it has been replaced by the program NETPATH.

SYSTEM REQUIREMENTS

Intel 80i86 based computer with 640 Kb RAM.

Developers: D.L. Parkhurst, et al. (U.S. Geological Survey).