Watershed tool not nesting catchments

[BrandyEverett]

I am trying to use the watershed tool to create watershed catchments of several sites along streams. I've used the tool with a 10m DEM.

I have filled the DEM, used the flow direction tool, the flow accumulation tool, and have snapped the pour points. The pour points look to be at a the correct spots on the highest accumulation point.

When I then run the watershed tool, making sure that in the environment to use the flow direction in the processing extent and snap raster selections, the catchments do not nest correctly.

[DanPatterson]

do you have a screen grab of the situation?

[TaniaLopezCantu]

Hi BrandyEverett,

Could you please share a screenshot of the Watershed tool output, and if possible, include the Input Pour Points visible as well?

If by nested watersheds you mean that the catchment for a given pour point should include all upstream areas, the ArcGIS Pro Watershed tool does not produce this result when multiple pour points are located along the same stream. Instead, the tool generates a separate catchment for each pour point. 

When pour points are upstream of another pour point, the tool delineates individual subcatchments for those upstream points. Then, starting from the boundaries of those subcatchments, it delineates the catchment for the downstream pour point. You can try running the tool one pour point at a time, beginning with the most downstream point. For a single pour point, the tool will include the entire catchment area draining to that location.

Please let me know if I interpreted wrongly your question and share with us more details on the input, the watershed output and what you expect. 

Thank you,

Tania

[BrandyEverett]

Please see the attached screenshot. For example, site IR59's catchment should encompass all other catchments (except Baron & Watts). Is there a way to get nested watershed catchments, i.e. force the watershed tool to not start from the boundaries of the upstream subcatchments without having to run each individual pour point? I have  ~1200 sites that need their subcatchments generated and running each pour point individually is not feasible. 

[TaniaLopezCantu]

Hi Brandy,

Thank you for your patience. I understand your problem and what is the expected output you are looking for. Unfortunately, with the Watershed tool, there is no other solution but to run the tool with one point at a time, as I mentioned earlier.

There's another solution that does not use the Spatial Analyst toolbox, Hydrology toolset, Watershed tool, but the Ready to Use toolbox, Watershed tool (see the screenshot below from the Analysis ribbon, Geoprocessing section. You can also find the Ready to Use toolbox in the Geoprocessing pane, under Toolboxes. This tool is free to use.).

This tool returns the catchment polygons that you're looking for, but there's a drawback. This tool uses preprocessed hydrologic data that was derived from a preconditioned Digital Elevation Model (different resolutions across the globe) and it's not possible to use your own DEM. The resolution of the DEM used in the Ready to Use Watershed tool may be coarser than your DEM, but the resulting catchments may be sufficiently detail for your analysis.

Hope this is helpful! 

Best Regards,

Tania