NAME
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.
METHODS
Load computations are performed by application of the mid-interval
method (Porterfield, 1972) to concentration data interpolated
(if necessary) to the same temporal frequency as the streamflow
time series. Cross-section coefficients may be applied as a
function of time, streamflow, or both, to account for systematic
bias in measured concentrations relative to true mean concentrations
in the stream cross section.
DATA REQUIREMENTS
A streamflow time series must be provided in card-image format.
Concentration data and associated metadata may be entered in
card-image format or in a special tab-separated format. Concentration
data can be irregularly spaced in time.
OUTPUT OPTIONS
Card-image files of daily constituent loads and daily mean
concentrations can be output. Other options include unit data
and printable files or printed output.
SYSTEM REQUIREMENTS
The GCLAS software is written in Java. Version 1.5.X or higher
of the Java Runtime Environment (JRE) must be installed in order
to run GCLAS at version 1.5e and above. The software has
run successfully under Microsoft Windows 95,98, and NT 4.0, XP,
and Sun Solaris 8 and above. GCLAS has not been tested with
other computer operating systems. 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.
HISTORY
Version 1.05e 2007/01/2 - First public release. This version addresses the following
bugs and enhancements:
o Program updated to work with up to JRE 1.5.x.
o Modified input templates to make creating GCLAS input files easier.
o Added support for new parameters.
o Made updates to the GUI.
o Added direct printing of load table under Windows.
o Added new data export options.
o Added checks to improve program error handling.
Version 1.05d 2004/04/30 - This version addresses the following
bugs and enhancements:
o Program updated to work with JRE 1.4.x.
o Added ability to import replicate sample values with identical date and
time stamps. Second sample's time is incremented by one second
to prevent identical date/time hash.
o Added ability to output unit-value card images of computed
concentration and constituent discharge.
o Modified gcl input routines to eliminate error caused by missing
end delimiters.
o Changed error messages to make them more understandable.
o Added a new input template.
o Updated help files to reflect changes.
Version 1.05 2003/02/07 -
o A new report was added to the loading table.
o Corrected a problem with loads computed for select instances of days with
incomplete streamflow and (or) concentration data, and where the load-
computation period specified included partial days.
o Modifed card-image output to prevent output of data for days where data
of load-computation period limits period respresented to less than 23 hours.
o Updated help files to reflect changes.
o Added parameters to parameter code dictionary.
o Replaced deprecated methods.
Version 1.04 2002/07/18 -
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
REFERENCES
Porterfield George, 1972, Computation of fluvial-sediment
discharge: U.S. Geological Survey Techniques of Water-
Resources Investigations, book 3, chap. C3, 66 p.
DOCUMENTATION
Koltun, G.F., Eberle, M., Gray, J.R., Glysson, G.D., 2006,
User's manual for the Graphical Constituent Loading
Analysis System (GCLAS), U.S. Geological Survey
Techniques and Methods, 4-C1, 51 p.
USGS Techniques and Methods 4-C1, (PDF)(918 KB).
CONTACTS
U.S. Geological Survey
Office of Surface Water
415 National Center
Reston, VA 20192
email: h2osoft@usgs.gov
Page created: 01/24/2007
