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Rain units

Posted by Valter Albino on August 23, 2013 at 1:59pm

Hi
I do have one question. Why each time i create a file in SI units and set rain to mm, leave the program, and then open the SWMM (5.0.022) file, and the rain units are in inches (instead of mm), altought the flow units are in LPS?
Thanks in advance.
Valter.

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Replies

  • Valter Albino August 23, 2013 at 4:17pm

    O.K., I understand that. It's fine, because it does not matter to the simulation, in this case.
    Thank you.
    Regards.

  • Robert Dickinson August 23, 2013 at 3:32pm

    The EPA explained that it should work this way, the units only refer to a file.  If you do not use a FILE then you are stuck with looking at INCHES but it does not matter to the simulation.

    Are you referring to the Rain Units property of a Rain Gage? Those only apply when one selects the FILE option for the Data Source (and then, only to rainfall files in user-supplied format). If you save a project where a rain gage has a FILE as a Data Source and the Rain Units are in mm, the same units will show up the next time you open the project. Otherwise they show up as inches, since that’s the default when the FILE option isn’t being used.

  • Robert Dickinson August 23, 2013 at 2:54pm

    Yes, it also does not work for me.  It keeps coming back as IN instead of MM, it is always MM in the engine for LPS or CMS units, however.

    ************************** Volume Depth
    Runoff Quantity Continuity hectare-m mm
    ************************** --------- -------
    Total Precipitation ...... 0.030 8.680
    Evaporation Loss ......... 0.000 0.000
    Infiltration Loss ........ 0.001 0.200
    Surface Runoff ........... 0.029 8.407
    Final Surface Storage .... 0.000 0.079
    Continuity Error (%) ..... -0.070

  • Robert Dickinson August 23, 2013 at 2:05pm

    I have not seen that but in the engine if the flow units are SI then the rainfall units are automatically mm even if it says inches in the interface.  it will be nice to get rid of inches totally eventually?

    • Valter Albino > Robert Dickinson August 23, 2013 at 2:26pm

      Thank you dear Bob.

      Yes, just SI, should be enough.

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