GROUND WATER -- Release of Water-Resources Investigations Report 94-4169, "An Interactive Code (NETPATH) for Modeling Net Geochemical 



In Reply Refer To:                       January 17, 1995
Mail Stop 411



OFFICE OF GROUND WATER TECHNICAL MEMORANDUM NO. 95.03

Subject:  GROUND WATER -- Release of Water-Resources
          Investigations Report 94-4169, "An Interactive
          Code (NETPATH) for Modeling Net Geochemical
          Reactions Along a Flow Path--Version 2.0"
          by L. Niel Plummer, Eric C. Prestemon, and
          David L. Parkhurst

The subject report describes a new version of the NETPATH
geochemical model.  NETPATH evaluates geochemical mass-
balance reactions along a hydrologic flow path that can
account for the observed chemical and isotopic differences
between the initial and final water compositions.
Radiocarbon dating of ground water is extensively treated
in NETPATH.  This new version replaces all previous
versions.  This version adds many new features, including
the ability to model reactions with nitrogen isotopes, the
ability to compute mixing fractions of up to five initial
waters, and a generalized aqueous speciation model that is
defined externally.  We recommend that this report be
brought to the attention of technical and management
personnel concerned with ground-water geochemistry.

The Hydrologic Analysis Support Section (HASS) is handling
the distribution of NETPATH within the Water Resources
Division.  To obtain the program for use on Data General
computers, connect to hassrvares.er.usgs.gov/ by anonymous
ftp.  Then retrieve files netpath.tar.Z and readme.netpath
from the pub/GEOCHEM directory.  The readme file contains
installation instructions.  It is recommended that the
local system administrator install NETPATH in
/usr/opt/wrdapp so that all local users will have access to
this new version of NETPATH.  A DOS version of NETPATH is
available in the pub/GEOCHEM/DOS/netpath directory on the
same workstation.  If there are problems installing the
software, contact HASS by electronic mail (wrdapp) or by
telephone (Steve Regan 703-648-5896).

Development copies of the DOS and UNIX versions of NETPATH
and other geochemical modeling software are maintained at
the internet address ftp brrcrftp.cr.usgs.gov as described in
the report.  A postscript version of the report is included
in the software distribution.

Additional copies of the report are available from the
authors.


                              /s/
                              William M. Alley
                              Chief, Office of Ground Water

Distribution:  A, B, PO, and S (memo only)
               FO (memo and report)