External Input File for SWMM

I have 8 subcatchments in a watershed and all these 8 subcatchments have 8 different curve number values(infiltration model).I want to vary the curve number values and look at the change in the associated hydrograph. Can you kindly suggest me in which programming language I should write the code so that it is possible to vary the Curve number values through that code instead of manually changing each subcatchemnt values.The total iterations of vhange in curve number values will be 256 so manually doing this will take a lot of time.Writing the code wont be that difficult.I just want to know in which language I should do it(Like C,Matlab,etc.).


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  • You can do this in any language but I will mention an Excel option:

    1. There is a direct link between SWMM5 and Excel - see the tools menu

    2. You can write an Excel Macro to export the SWMM 5 input file to different files using a random number generator to have different CN

    3. You can make a batch file to run the model SWMM5 CN1.DAT CN1.OUT etc and then collect the RPT files to make your 256 comparisons


    • Thankyou for the prompt reply, I have added the excel add-in,I dont want to randomly generate the values,basically I will put 2 values( max and min) for every curve number(both values predecided by me) and take all the different combinations,that will be a total of 2^8=256 (as I have 8 sub catchments),is it still possible by excel.Thankyou for all the help

      • In the macro you would store your CN's on a separate worksheet.  In the macro I would  export my SWMM 5 inp file with different CN's from the Worksheet -as defined by you.  You have one worksheet that is exported 256 times.  I hope this is clear. 

        Here is one more Matlab reference as well


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