An interactive code (NETPATH) for modeling NET geochemical reactions along a flow PATH

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 proportion of two 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.Every possible geochemical mass balance reaction model is examined between selected evolutionary waters for a set of chemical and isotopic constraints, and a set of plausible phases in the system.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, and strontium isotopic compositions at the end point, including radiocarbon dating.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 that demonstrate most of the applications and features of NETPATH.The codes DB and NETPATH can be executed on and IBM PC1 or compatible microcomputer.1 The use of trade, brand or product names in this report is for identification purposes only and does not constitute endorsement by the U.S. Geological Survey. Essential FilesThe files listed below are required in compiling and running DB and NETPATH.If it is not necessary to recompile DB and NETPATH, only the files DB.EXE, NETPATH.EXE, NETPATH.DAT, and WATEQF.DAT need to be resident in the directory to run the programs DB and NETPATH.If the file NETPATH.DAT is not found in the directory, NETPATH creates an empty NETPATH.DAT file.DB.FOR: This is the Fortran 77 source code of the database editing program, DB.The hydrochemical data from field information are entered and saved in the .LON file for later manipulation.DB.FOR also includes the program WATEQFP which is a modified version of ion-association model, WATEQF (Plummer and others, 1976), used to calculate the distribution of aqueous species and construct