Water Resources of the United States
GCLAS (Graphical Constituent Loading Analysis System)
is a program designed primarily to compute daily and annual loadings of
constituents transported in streamflow. Use of GCLAS is appopriate when
concentration data are collected at relatively high frequency (i.e.
approximately daily to more frequent samples depending on the temporal
variability of streamflow and concentrations) and concentration data are nearly or
completely free of censored (e.g. "less than") values.
Concentration data can be at equal or unequal time intervals. Depending
on the frequency with which water-quality data are collected,
computation of daily constituent loads can be independent of, to highly
dependent on human interpretation of the relation between streamflow and constituent transport.
GCLAS provides a
visual environment for evaluating the relation between covariate time
series and the constituent chemograph. GCLAS has an interactive
graphical interface that permits easy entry of estimated values and
provides tools to aid in making those estimates. Some of the features
of 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 a variety of
constituents, (4) the ability to easily view data related to the
chemograph at varying levels of detail, and (5) the ability to readily
display covariate time-series data to provide enhanced visual cues for
drawing the constituent chemograph.
GCLAS installer packaged for Unix and Windows (current version that creates tab-delimited [rdb] outputs)
gclas_install_2_00.jar (4.7 MB)
GCLAS installer packaged for Unix and Windows (legacy version that creates card-image outputs)
Note: Some browsers rename jar files
with a ".zip" extension. If that happens, change the extension back to
".jar" before installation.
The Java Runtime Environment (JRE) Version 6 or higher is recommended to run GCLAS. The latest version for Solaris, Linux, and
Microsoft Windows platforms can be downloaded from http://www.java.com.
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, Portable Document Format (PDF)
Point of contact for GCLAS:
Office of Surface Water
12201 Sunrise Valley Drive
Mail Stop 415
Reston, VA 20192
(electronic mail: firstname.lastname@example.org)