3

I put a pourpoint at the end of a headwater stream, then another further downstream that is fed by that headwater stream plus two others.

Obviously the pourpoint further downstream is going to share a watershed with the headwater pourpoint.

Is there a way of identifying the individual watersheds so that the watershed of the pourpoint further downstream includes that headwater?

I want to be able to do many pourpoints together and get the real watersheds, but they always are cut off by the overlaps.

I DO NOT have Arc Hydro because I cannot get it to install properly and haven't been able to find instructions on how to do so - see https://gis.stackexchange.com/questions/137538/installing-arc-hydro-problems.

I'm using ArcMap 10.2.2

  • Just do them all in 1 go. Convert points to grid using integer field and use standard tool to get watersheds – FelixIP Mar 4 '15 at 8:57
  • which tool is that? And what do you mean by integer field? Could you describe in more detail, please? – StreamSide Mar 5 '15 at 16:29
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    @StreamSide I recall running into this same problem once. About five years ago I wrote a tool called Unnest Basins for an older version of some software that I created (see unc.edu/courses/2010spring/geog/591/001/software/bin/Help/…) If this sounds like the kind of operation that satisfies your request, I can look into reimplementing the tool in the current version of the open-source GIS Whitebox GAT. Just let me know. – WhiteboxDev Mar 11 '15 at 21:11
  • Just as an update for future readers looking for an answer, I did reimplement the Unnest Basins tool as a plugin for Whitebox GAT 3.3 (uoguelph.ca/~hydrogeo/Whitebox) written in JavaScript, with the source code available here: github.com/jblindsay/whitebox-geospatial-analysis-tools/blob/… – WhiteboxDev May 18 '16 at 17:36
1

All the tools mentioned below (in capitals) are from Spatial Analyst-Hydrology toolbox.

  1. FILL digital elevation model. Output - 'filled'
  2. Calculate FLOW DIRECTION raster using 'filled'. Output - 'fdir'
  3. Calculate FLOW ACCUMULATION raster using 'fdir'. Output 'facc'. Apply classified symbology to 'facc' to see where your 'streams' are. The picture below shows terrain with 'facc' on the top (blue). Note that low accumulation cells shown with transparent color:

enter image description here

  1. Create points at your discharge locations using 'facc' to place them nicely in the 'stream'. Points shown have field [pointid], type of the field is short integer. I labelled them using values stored in this field (0,1,2,3)
  2. Calculate WATERSHED. Output 'wsheds' enter image description here Apply Raster to Polygon (conversion tools) to 'wsheds' to get this. Note watersheds are labelled by their discharge pointIDenter image description here
  • It won't work unless you access "environments" and access processing extent. It will process any watersheds for all the points, but they will not be allowed to overlap. In other words, one point's watershed from far downstream should include the whole upstream area, but if there is another point upstream, that area is omitted. It simply shares a border with that upstream watershed. It's difficult when wanting to calculate watershed areas from several points along a stream. – StreamSide Mar 5 '15 at 22:17
  • Remove point 3 and see what happens – FelixIP Mar 5 '15 at 22:50
  • I don't know what you're referring to. – StreamSide Mar 6 '15 at 17:21

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