Following is the appearance of the Point Sources tab of the River Coefficients dialog:
Following is a description of the parameters associated with Point Sources. Refer to the main River Coefficients page for information on other categories of coefficients. To save the changes made when closing this dialog, click OK. To ignore changes, click Cancel.
When Point Sources is clicked, the dialog shows a list of the point source dischargers to this river segment. The effluent data for each discharger is stored in a separate file with a PTS extension. As shown, a river segment can accept multiple point source discharges. To add a file to the list, click on the corresponding Add button and select the file to add. To remove a file from the list, click on it and click the corresponding Remove button. The point source data files are usually named based on an NPDES permit number.
After selecting a point source file from the list, a number of options will become activate below. Following is a description of these options:
Internal means that the water for the point source is taken from this river segment and then returned.
External means that the water for the point source is introduced to the river from an outside source.
Zero means that the loading for all constituents not listed in the data file is assumed to be zero.
River Ambient means that the loading for all constituents not listed in the data is assumed to be the same as the river concentrations. This option is required with an internal water source.
Point source load from a sewage treatment plant or an industrial facility is from an external source. A thermal discharge, on the other hand, is from an internal source because the power plant withdraws water from a stream segment within the basin, adds heat or other chemical constituents, and discharges it back to a different location. For an internal source discharge, the line underneath the list changes to “Specify changes in temperature and loading added”. In other words, the numbers in the point source file represent the load increase to the temperature and other water quality constituents. “River ambient” should be selected for an internal point source so that the loading for the unspecified constituents is the same as the river from which the water was drawn. For external point sources, the actual temperature and loading of the point source is specified in the data file. For external sources, “Zero” should be selected under unspecified constituents.
The location of the point sources can be seen on the watershed map by selecting View / Point Sources from the main menu. To view point source data, double click on a white dot for a specific discharger from the map display or select a file from the list within the data module.
When the Apply Changes To Selected Rivers button is checked, changes made to the coefficients of the river being edited will be made to all selected rivers. When the Apply Changes To All Rivers button is checked, changes made to the coefficients of the river being edited will be made to all rivers.