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. 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.