Error whatershed delineation

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Jana Corominas

Jan 12, 2024, 11:40:57 AMJan 12
to wrf-hydro_users
Hello everyone,
I have done the preprocessing part of the WRF-Hydro with ArcGIS Pro and WRFHydro Gis Preprocessor v5.2.0. It is the first time I have used "Channel initiation points feature class" to define the most upstream points of my channels of interest to help the model delineate the watershed.
Although the upstream subbasins are well defined (better than without the channel initiation points), the outlet of the basin shows error comparing with the real streams. 
Is it all because of the DEM (mine has 5 m resolution)? 
Is there a way to give extra data to the preprocessor tool to help the delineation?
Any solution to this problem will be helpful,
Thanks a lot,

Kevin Sampson

Jan 12, 2024, 1:57:15 PMJan 12

Yes, the streams in the resulting CHANNELGRID variable will be based solely on your initiation points and the flow direction grid (FLOWDIRECTION) at the resolution of your defined WRF-Hydro routing grid. I assume that the error you see is a spatial offset from the location of the true channel locations when compared to a basemap. This can be fixed in a number of ways. Is your input DEM finer than your routing grid resolution? If not, then perhaps a finer resolution input DEM or a hydrologically processed DEM is justified here. Does your DEM exhibit the correct channel locations based on topography? If so, then perhaps the pit-filling process is causing hydro-flattening in the areas you are examining. You could try changing the algorithm used in the interpolation process. 

Some other methods are to burn streams into your input DEM where you know them to be. This is a heavy-handed approach, but is sometimes necessary to properly locate known channel locations. 

Kevin Sampson, GISP
Associate Scientist
NSF National Center for Atmospheric Research
Boulder, Colorado

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