I have a number of data points showing the placement of stream gauges. What I'd like to do is to delineate the subwatershed for each point, so that when rainfall events occur, I can see the drainage area for water that will travel through that stream gauge.

I have my clipped DEM, to my area of study (in red), as well as the first stream gauge point I'd like to use for delineation (green):

enter image description here

However, I've tried a handful of guides for this delineation, and each time the output is not correct.

I believe that my main issue is that when the flow accumulation is performed, it is only picking up on the largest nearby river, and not some of the smaller tributaries. The gauge/pour point I'm interested in is very far from the nearest accumulation point:

enter image description here

Some of the steps I've tried: Clip DEM, Fill DEM, Flow Direction, Flow Accumulation, Pour Point (using the green gauge point as the pour point), and Watershed.

I've also followed this guide before: https://imap.maryland.gov/Documents/Training/LiDAR_Mod7_DelineatingWatersheds.pdf

Any suggestions on what I'm doing wrong, or maybe someone has a better guide/ set of steps to get this done?

  • 1
    Classify flow accumulation in 2 classes and manually move you gauge to nearest channel.
    – FelixIP
    Dec 2, 2019 at 19:43
  • To aid in your pour point placement: I find it easier to identify the smaller tributaries by opening up the flow accumulation raster layer properties-->Symbology tab--> change the "stretch type" to 'percent clip' or 'standard deviations' or maybe even 'histogram equalize' and also specify that you want the statistics "From Current Display Extent". This will highlight flow lines more dynamically as you zoom in and pan around.
    – Zipper1365
    Dec 4, 2019 at 15:50

1 Answer 1


Found the answer: The DEM was quite large, and the Flow Accumulation tool was focusing on the main river, and 'ignoring' the smaller tributaries. The solution was to crop the DEM to specific areas so that the accumulation could pick up on the tributaries. The above steps (Clip DEM, Fill DEM, Flow Direction, Flow Accumulation, Pour Point, Watershed) worked properly.

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