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Using HydrCad as a calibration tool

Using HydrCad as a calibration tool

Using HydrCad as a calibration tool

In order to use HydroCad as a tool for calibrating the TR-20 hydrology model it would be necessary to vary all of the parameters used as input to TR-20. For example, I would like to model an existing, urban, gaged drainage basin which has an area of  8,525 acres  ( 13.32 sq mi ). I have rainfall data from 6 gages over a period of two years. I also have stream flow data for the same period.

With this data I can generate "design storms" with which to calibrate TR-20. This is not easy ( it is tedious and error prone ) using text files, but it can be done.

I can also vary the time of concentration ( Tc) starting with an initial guess of 120 minutes.
I can also vary the Curve Number (CN) starting with an initial guess of CN=80.

The problem arises from the fact that HydroCad ( Ver. 8.50 ) does not allow me to vary the peak attenuation factor (K').    

Rather it uses the "standard" K' = 484.  It allows some other values, but it does not allow any possible value from, say, 200 to 600.  

Has anyone used HydroCad in this way ?
Can it be used in this way or should I try a different model, such as SMADA, SWMM, or some thing else?
Does HydroCad 9.0 or later allow this kind of analysis ?
 Are there any plans to modify it so that it could ?

Any help or suggestions would be appreciated.

RE: Using HydrCad as a calibration tool

The peak factor is a function of the Unit Hydrograph.  If you wish to use a different peak factor with HydroCAD, just specify a different unit hydrograph, exactly as you would with TR-20.

The Delmarva UH is the most common alternative, and is preinstalled with HydroCAD and can be selected on the calculation settings screen.  Other UH tables can be downloaded from www.hydrocad.net/uhtables.htm


Peter Smart
HydroCAD Software

RE: Using HydrCad as a calibration tool

Thank you Mr. Smart.

Your suggestions are helpful but I'm finding it very difficult to do what I'm trying to do with HydroCad (8.5). This is partly because in order to compare hydrographs I have been trying to use both HydroCad and Excel. It is NOT easy to get information from one program to the other. Alas, I wish it was.

It might help you to understand what I'm trying to do by looking at the uploaded .pdf file.

Thank you again.

RE: Using HydrCad as a calibration tool

To export a hydrograph from HydroCAD to a spreadsheet:
1)open the tabular hydrograph report
2)click the "Export" button
3)select the CSV format.

You can also compare hydropgraphs within HydroCAD:  Just select 2 (or more) nodes to compare and click the "Comparision Report" button on the toolbar.

If the data you want to compare comes from outside HydroCAD, you could import it with a link.  This is probably much easier than trying to do the comparison in excel.

Peter Smart
HydroCAD Software

RE: Using HydrCad as a calibration tool

Thanks again,
I have tried your suggestions 1), 2) and 3) but without much success, so far.

As to comparing hydrographs within HydroCad, rather than Excel or some other spreadsheet, I find it much more useful to do the comparison in Excel. Within Excel I can copy and paste data freely. Retyping huge amounts of data is not only boring but very likely to lead to errors.  Within Excel I can also do other things like calculate differences between sets of data, calculate the "intergral square error" referred to in Mr. Singhofen's report, and plot the comparable hydrographs at any scale I wish. None of these things are easy and some, are not even possible, within HydroCad.

HydroCad is a good program in many ways but it appears it may not be the best way to accomplish this particular task. Easy exchange of data would help a lot but perhaps that is a forlorn hope.

Thank you for all your help, nevertheless.

RE: Using HydrCad as a calibration tool

Export to CSV is very easy.  After you create the file, open it with Excel and you'll see the data in columns.   What part of the process did you have trouble with?

Peter Smart
HydroCAD Software

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