An Interactive Code (NETPATH) For Modeling NET Geochemical Reactions
Along a Flow PATH Version 2.0

By L.N. Plummer, E.C. Prestemon, and D.L. Parkhurst

U.S. Geological Survey Water-Resources Investigations Report 94-4169, 1994.

ABSTRACT

NETPATH is an interactive Fortran 77 computer program used to
interpret net geochemical mass-balance reactions between an initial
and final water along a hydrologic flow path. Alternatively, NETPATH
computes the mixing proportions of two to five initial waters and net
geochemical reactions that can account for the observed composition of
a final water. The program utilizes previously defined chemical and
isotopic data for waters from a hydrochemical system. For a set of
minerals and (or) gas phases hypothesized to be the reactive phases in
the system, NETPATH calculates the mass transfers in every possible
combination of the selected phases that accounts for the observed
changes in the selected chemical and (or) isotopic compositions
observed along the flow path. The calculations are of use in
interpreting geochemical reactions, mixing proportions, evaporation
and (or) dilution of waters, and mineral mass transfer in the chemical
and isotopic evolution of natural and environmental waters. Rayleigh
distillation calculations are applied to each mass-balance model that
satisfies the constraints to predict carbon, sulfur, nitrogen, and
strontium isotopic compositions at the end point, including
radiocarbon dating. DB is an interactive Fortran 77 computer program
used to enter analytical data into NETPATH, and calculate the
distribution of species in aqueous solution.  This report describes
the types of problems that can be solved, the methods used to solve
problems, and the features available in the program to facilitate
these solutions. Examples are presented to demonstrate most of the
applications and features of NETPATH. The codes DB and NETPATH can be
executed in the UNIX or DOS environment. This report replaces
U.S. Geological Survey Water Resources Investigations Report 91-4078,
by Plummer and others, which described the original release of
NETPATH, version 1.0 (dated December, 1991), and documents revisions
and enhancements that are included in version 2.0.