Introducing GCLAS

GCLAS (Graphical Constituent Loading Analysis System) 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. GCLAS differs substantially from SEDCALC, its predecessor, in four important ways:

• It is far more visual. GCLAS simultaneously displays tabulated data and graphs of those data during the working session. Rather than type in command lines to do computations and then generate plots to see the results, you can manipulate graphical displays directly with a mouse or edit data tables. And, because the graphs and tables are dynamically linked, you can see immediate display of data-manipulation results in both graphs and tables. Data points and curves for an entire year and a subset of that year are usually on display throughout an entire working session.

• It provides a more comprehensive set of tools. Besides providing the editable graphs and tables already mentioned, GCLAS can:
  1. display transport curves for the streamflow and concentration data being worked, giving you a "reality check" for adding or repositioning estimated data points on a concentration curve,

  2. compute and/or apply cross-section ("box") coefficients to the displayed data,

  3. compute loads for the year or any part of the year being worked, and export the load data to files for subsequent statistical analysis.
• It can handle streamflow record that includes zero flows and reverse flows. Because you can resize, rescale, and zoom in on graphs in GCLAS, logarithmic transformations needed for SEDCALC graphical displays are no longer necessary in GCLAS, so working with zero and reverse flows is feasible. (Some logarithmic transforms for data manipulation are available as GCLAS options, however.)

• Loading calculations can be made for constituents other than sediment.

So that GCLAS can be installed on a variety of hardware with minimal customization, it is based on Java[TM] technology.* Although the GCLAS visual display is similar to other windows-type interfaces, it differs in some respects. (See Overview of GCLAS window and panel interface.)

*Java is a trademark of Sun Microsystems, Inc. in the United States and other countries.