Release of Graphical Constituent Loading Analysis System (GCLAS) Software

In Reply Refer To: 
Office of Information 
Mail Stop 437 

MEMORANDUM 

March 21, 2001


To:           Data Chiefs 
          District Surface Water Specialists 
          District Water Quality Specialists 
          Regional Surface Water Specialists 
          Regional Water Quality Specialists 

From:     Stephen F. Blanchard /signed/ 
      Acting Chief, Office of Information 

Subject:  Release of Graphical Constituent Loading Analysis System 
(GCLAS) Software 

This memorandum announces the release of the Graphical Constituent Loading 
Analysis System (GCLAS) for internal use within the Water Resources 
Discipline (WRD).  GCLAS is a software package designed to aid in 
analyzing water-quality time-series data and computing daily loads of 
sediment or other stream-water constituents.  The development of GCLAS is 
a joint effort of the Hydrologic Analysis Software Support Program, and 
the Offices of Surface Water and Water Quality.  GCLAS differs 
substantially from its predecessor, SEDCALC, in four important ways:  (1) 
GCLAS is far more visual, (2) GCLAS provides a more comprehensive set of 
tools, (3) GCLAS can handle streamflow record that includes zero flows and 
reverse flows, and (4) GCLAS will allow for computations with constituents 
other than sediment in a future release. 

GCLAS was developed in part to facilitate computations of daily sediment 
records.  Hydrographers at the Cascades Volcano Observatory, who have been 
using a recent version of GCLAS, report an appreciable timesaving over 
previous years for processing a sediment record.  It is our hope that the 
release and implementation of GCLAS within the WRD will greatly improve 
the efficiency of the process for working sediment records and for 
computing loads of selected water quality constituents. 

To obtain GCLAS, to go the HASS internal page at 

http://hassrvares.er.usgs.gov/ and download the software.  If you have 
questions about the software, please contact Greg Koltun at (614) 430-7708 
or Tom McKallip at (703) 648-4876 or send e-mail to h2osoft@usgs.gov. 

Copy to:        WRD Senior Staff 
                Branch and Office Chiefs 
                District Chiefs 



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Steve Blanchard                                     
Acting Chief,  Office of Information        
U.S. Geological Survey                          
National Center, MS 440                      Phone: 703-648-5629 
Reston, VA 20192                                Fax:     703-648-5644
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