UPM Threshold

Before running a river impact assessment you must specify the thresholds against which the levels of pollutants in the water are to be tested. This information is held in InfoWorks ICM in a UPM threshold item and includes thresholds for mass balance frequency analysis and fundamental intermittent standards.

Data for the UPM threshold item is entered in the UPM Thresholds dialog, which has two tabs: River Ecosystems and Fundamental Stds. It is possible to create a new UPM river data item, and edit, import and export an existing one.

Creating a new UPM threshold item

To create a new UPM threshold item:

1. Right-click in the Explorer Window containing the model group for which a new item is to be created, and select the New InfoWorks | UPM Threshold from the context menu. A New Name dialog appears.
2. Enter the name that is to be used to identify the new UPM threshold and click OK. The newly created item now appears in the database tree in the Explorer Window.
3. Either double-click on the new UPM threshold item, or right click on it and select Open from the context menu, and the UPM Threshold Data dialog is then displayed.
4. In the River Ecosystems tab, select one of five fixed environmental standards from the drop-down list. Alternatively, select the User Defined option to define your own set of thresholds.
5. If you selected the User Defined option, enter the percentage of time for which the concentrations of pollutant in the water may exceed the thresholds in the Percentile field. Enter the thresholds for BOD and Total ammonia. If you also want to test the level of un-ionised ammonia, click on the Model Un-ionised Ammonia check box and enter a threshold.
6. Click on the Fundamental Stds tab to set up fundamental intermittent standards.
7. Select one of three fixed environmental standards. Alternatively, select the User Defined option to define your own set of thresholds.
8. For the User Defined option, enter a concentration level for each combination of impact duration and return period. The impact duration is the period for which the given level of concentration can be tolerated; the return period specifies the frequency with which this level may be exceeded. For example, the top left cell of the Un-ionised Ammonia table gives the concentration for an impact duration of 1 hour and a return period of one month; this level may be exceeded for no more than 12 one-hour periods per year. The entries in the Dissolved Oxygen table are minimum values; those in the Un-ionised Ammonia table are maximum values.
9. Close the dialog and confirm that you want to save the changes.

Editing a UPM threshold item

The UPM threshold item can be edited by either double-clicking on the item in the Explorer Window or by right-clicking on it and selecting Open from the context menu. The UPM Threshold Data dialog is then displayed which can be used to update the data as required.

Importing a UPM threshold item

To import an existing UPM threshold item from an existing InfoWorks event file:

1. Right-click in the Explorer Window containing the model group for which a UPM threshold item is to be imported, and select the Import InfoWorks | UPM Threshold | From events file from the context menu. A standard Windows Open File window appears.
2. Specify the location and name of the event file (.upt) containing the UPM threshold data which is to be imported and click OK. The imported item now appears in the database tree in the Explorer Window.

Exporting a UPM threshold item

To export a UPM threshold item to an InfoWorks event file:

1. Right-click in the Explorer Window containing the UPM threshold item which is to be exported, and select the Export | To InfoWorks file from the context menu. A standard Windows Save As window appears.
2. Specify the location and name for the event file (.upt) which is to contain the exported the UPM threshold item, and then click OK to export the file.