scope of merging some sub-watershed and re-run the swat model

[dipak]

Dear SWAT user

I have successfully run the SWAT model, then merged some sub-watersheds and rerun the model. I found  number of sub-watershed remains same as it was before merging. What I did is simply merged some sub-watersheds in ArcSWAT interface , write all input files then again run the model successfully. Why the number of sub-watershed is not changing in my output files after merging? Is there any procedural error exists in my approach? Please share some of your valuable experiences regarding same.

thanks

[dirombihon]

I think the number of subwatersheds are picked up by SWAT during you delineation processes. The merging process you did after that is just ArcGIS process, it doesn't have anything to do with SWAT. Therefore, SWAT still knows the number of subwatersheds created during the delineation process. So, if you want to change your subwatershed set-up, you need to redo the delineation processes based on the DEM or predefined river network and subwatersheds.

best

[Jaswant]

Hi Deepak,

Dirombihon is right !!  What you did is just changing the the GIS-interface visualization only. The swat still has the same number of sub-watersheds.

Now you do one thing, Save as your merged sub-watershed and reach shape files with some  names as two different shape files. Now you create another swat project and in place of delineation of stream network/sub-watersheds, you import your merged subwatershed and reach shape files. In SWAT, there is option of predefined stream network. It worked in my case.

All the best,

Jaswant

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[Dipak Samal]

Thank you very much Dirombihon for your reply. You are right, I merged two sub-basin polygons after successful running of the model, then rewrite all the files and rerun the model with modified sub-basin(merged) boundary. 

Now it is confirmed that modification to any basin/sub-basin boundary is not at all possible after the model set up. If it requires to do so, we need to go back and redo delineation  process.  . 

Thanks

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[Dipak Samal]

Hi Jaswant, I will try your proposed method.

Thanks