Office of Ground Water Tech MM 96.01

To: "File WRD Archive, , Reston, VA "
Subject: Office of Ground Water Tech MM 96.01
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Date: Thu, 01 Feb 1996 15:01:22 -0500
From: "Velvie E Stockdale, Office Automation Assistant, Reston, VA "

In Reply Refer To:                       January 26, 1996
Mail Stop 411


Subject:  GROUND WATER -- Release of Water-Resources 
          Investigations Report 95-4227, "User's guide to 
          PHREEQC-A computer program for speciation, 
          reaction-path, advective-transport, and inverse 
          geochemical calculations" by David L. Parkhurst

The subject report describes a new geochemical model named 
PHREEQC.  PHREEQC is derived from the Fortran program 
PHREEQE, but it has been completely rewritten in C with the 
addition of many new capabilities.  The new code has all 
the capabilities of PHREEQE and WATEQ4F.  Additional 
capabilities compared to PHREEQE include:  enhanced 
speciation modeling; inclusion of ion exchange, surface 
complexation, and gas bubble formation; keeping track of 
masses of minerals and determining the stable phase 
assemblage; and simple advective transport modeling in 
combination with the available chemistry.  In addition, the 
code is capable of the inverse modeling calculations, but 
not the isotopic calculations, included in NETPATH.  An 
enhancement not included in NETPATH is the ability to 
account for uncertainties in the analytical data used in 
inverse modeling.  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 PHREEQC within the Water Resources 
Division.  The software is accessible on the World Wide 
Web, using Mosaic or similar World Wide Web reader, from 
the internal Hydrologic Software page (http:// and by anonymous FTP from ( in the /pub/software/
geochemical/phreeqc/UNIX directory.  The README file in the 
distribution package contains installation instructions.  A 
postscript version of the report is also included in the 
distribution package.

The next WRDAPP tape from HASS, available in the next few 
weeks, will include PHREEQC.  If there are problems 
installing the software, contact HASS by electronic mail 
(h2osoft) or by telephone (Steve Regan 703-648-5896).

Development copies of the DOS and UNIX versions of PHREEQC 
and other geochemical modeling software are maintained at 
the internet address ftp as described in 
the report.  

Additional copies of the report are available from the 

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

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