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Watershed Area for Random Point

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08-15-2013 11:12 AM
LenDesson
Emerging Contributor
I took a DEM and made a Flow Direction waster from it, ran Sink, there were some, and ran Fill.  Re-ran Flow Direction.
What I am trying to do is find the Watershed for a random point (not necessarily a pour point).  If I locate my random point and then run the Watershed tool, the tool gives me a very small area which does not seem to represent all the upstream cells that drain to it. 

I found this really helpful link and though the processing extents were my problem, but I made sure to set those properly and I am stillgetting the small area result. 

http://forums.arcgis.com/threads/78317-Watershed-tool-returns-only-immediate-catchment-not-entire-up...

Any ideas or other ways to go about it?
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NeilAyres
MVP Alum
You need to use the snappour command / tool to snap your "random" pour point to a cell of highest accumulation within a certain radius.
If you just input any "random" point its likely that you will get many that have a quite tiny "watershed".
You will not see the small imperfections in your dem that are causing this.
N

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2 Replies
NeilAyres
MVP Alum
You need to use the snappour command / tool to snap your "random" pour point to a cell of highest accumulation within a certain radius.
If you just input any "random" point its likely that you will get many that have a quite tiny "watershed".
You will not see the small imperfections in your dem that are causing this.
N
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LenDesson
Emerging Contributor
You need to use the snappour command / tool to snap your "random" pour point to a cell of highest accumulation within a certain radius.
If you just input any "random" point its likely that you will get many that have a quite tiny "watershed".
You will not see the small imperfections in your dem that are causing this.
N


Yep, this was the step I was missing... the Snap Pour Points tool snapped my random point to the closest high accumulation flow line, returned a raster which I was able to feed in to the Watershed tool to delineate the real watershed.
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