GCLAS - Graphical Constituent Loading Analysis System
ABSTRACT
GCLAS aids in the computation of daily constituent loads
transported in streamflow. Due to the relative paucity with
which most water-quality data are collected, computation of
daily constituent loads is moderately to highly dependent on
human interpretation of the relation between stream
hydraulics and constituent transport. GCLAS provides a
visual environment for evaluating the relation between
hydraulic and other covariate time series and the
constituent chemograph. GCLAS replaces the computer program
SEDCALC, the prior USGS tool for constructing sediment
chemographs and computing suspended-sediment loads. GCLAS
has an interactive graphical interface that permits easy
entry of estimated values and provides new tools to aid in
making those estimates. Some of the improvements introduced
in GCLAS include (1) the ability to directly handle periods
of zero or reverse flow, (2) the ability to analyze and
apply coefficient adjustments to concentrations as a
function of time, streamflow, or both, (3) the ability to
compute discharges of constituents other than suspended
sediment, (4) the ability to easily view data related to the
chemograph at different levels of detail, and (5) the
ability to readily display covariate time-series data to
provide enhanced visual cues for drawing the constituent
chemograph.
METHOD
GCLAS captures in a software application the graphical
methods for computation of fluvial-sediment discharge
described by Porterfield (1972).
HISTORY
Version 1.04 2002/07/18 - This version addresses the following
bugs and enhancements:
o When rounded concentration data were output in card-image form
from the load table, the parameter code was output as the string
"undef" rather than 80154.
o When rounded concentration data were output in card-image form
from the load table, when attempting to write unrounded
concentration data, GCLAS used to cause an exception resulting
in a zero size report file as a result of the exception.
o Saving a .csv file as a .gcl file, caused an exception.
o When a date cell was edited with a new date and user pressed
"Enter", the time cell was set to computer system's time in GMT.
o If two data values occurred on the same day and one of the
data values was edited so that its time was earlier in the day
than the other value, then the water-quality table was not
resorted based on the new entered. Also, the graph was not drawn
properly. The data was shown correctly if they are saved to a
gpf file and re-read into GCLAS. In general, editing a time
cell was not causing a resort of the table based on the new time.
o Loads computed for partial days were not correct. The total
number of intervals used for discretization of the day was
used instead of the actual number of time intervals in the
partial day. (note: this bug only affected loads computed for
the first and last day of the computation period.)
o When loads were computed sequentially for at least two
discontinuous periods, the load table was improperly filled in
for the intervening days. These data were not output to card
images if card images were subsequently created.
o A merge was originally (pre-version 1.04) done by averaging
concentrations and coefficients and applying them at the minimum
streamflow associated with the merged coefficents and at the time
associated with the earliest time of the merged coefficients.
This was changed to make the streamflow associated with the merged
coefficient equal to the average streamflow.
o New parameters were added to the parameters table.
o The ability to use several different concentration and load units
was added.
o The user interface was cleaned up.
o The checkbox named "Include Est. pts" on the "Apply Coefficients"
tab was removed. The functionality for this checkbox was never
implemented. To provide the intended functionality,
a new "Options" menu was added. A "Default Representation" sub menu
was added under the "Options" menu cascading to 3 choices for the user
to select from: "Cross Section", "Single Vertical", or "Point".
Estimated values are assigned the representation chosen by the user.
Changing the default representation affects only those estimated values
that are entered after the change in default representation.
o The help files were updated to reflect the changes implemented in
this release.
Version 1.03 2001/08/13 - not released officially
Version 1.02 2001/04/18 - Corrected problems with saving and
reloading data. Corrected problem where ignored values
were still being used in computing daily loads.
Version 1.01 2001/03/25 - Corrected problem in which
discharge values were not interpolated when concentration
values were interactively added to the data set. Also
corrected problem in which concentration values that were
interactively deleted were not completely removed from
the data structure. If the data were then stored to and
reloaded from a GCLAS Project File or gcl file, the
previously deleted data were restored to the working data
set.
Version 1.0 2001/03/21 - Initial release
Version 1.b 2000/11/01 - Initial beta release
DATA REQUIREMENTS
Values of discharge and values of concentration. Discharge
values must be in card image format. Values of
concentration must be in the SEDDATA (2-CARD) format or a
gcl format. The gcl format is similar to the tab-delimited
rdb format and can be created by inserting header
information on top of columns of tabular data in a
spreadsheet.
OUTPUT OPTIONS
Card image files for daily constituent loads and daily mean
concentrations. Other output data are planned.
SYSTEM REQUIREMENTS
The GCLAS software is written in Java. Version 1.3.X
of the Java Runtime Environment (JRE) must be
installed in order to run GCLAS. The software has run
successfully under Microsoft Windows 95, 98, and NT 4.0, and
Sun Solaris 2.6. For other computer platforms, the
usability of GCLAS depends on the availability of JRE for
that platform. Although GCLAS is written entirely in Java,
it may not conform to the 100% Pure Java standard and may
not run properly on some operating systems.
REFERENCES
Porterfield George, 1972, Computation of fluvial-sediment
discharge: U.S. Geological Survey Techniques of Water-
Resources Investigations, book 3, chap. C3, 66 p.
CONTACTS
Operation and Distribution:
U.S. Geological Survey
Hydrologic Analysis Software Support Program
437 National Center
Reston, VA 20192
h2osoft@usgs.gov
Official versions of U.S. Geological Survey water-resources
analysis software are available for electronic retrieval via
the World Wide Web (WWW) at:
http://hassrvares.er.usgs.gov/
and via anonymous File Transfer Protocol (FTP) from:
hqwiftp.er.usgs.gov (path: /pub/software).
The WWW page and anonymous FTP directory from which the
GCLAS software can be retrieved are, respectively:
http://hassrvares.er.usgs.gov/gclas.html
--and--
/pub/software/ground_water/gclas
See
http://water.usgs.gov/software/ordering_documentation.html
for information on ordering printed copies of USGS
publications.