Watershed or subwatershed provides a good SDR Result?

Software Support
1

Could you justify why?. In the watersheds (vector) box, what is the good choice to add: single watershed boundary, or a watershed that contain many sub-watershed boundaries?. When I try SDR model using single watershed, the result is different from that of using sub-watershed.

2

Hi @Eshetu -

The watershed input to SDR is used in two ways:

1/ to clip the input data to the watershed boundary
2/ to aggregate the model results

If your single watershed boundary is the same outline as the many sub-watershed boundaries, then the only difference in results is that you’ll get results aggregated to one large watershed or aggregated to many sub-watersheds. The underlying per-pixel values should be the same.

It is up to you to decide whether it’s more useful for your analysis to aggregate to one larger or many smaller watersheds. You can also do the same aggregation manually, using a GIS Zonal Statistics tool.

~ Stacie

3

Dear Swolny, thank you so much for your timely reply. I tried both single and many sub-watersheds having the same boundary. Even when I used sub-watershed, the result is not aggregated at sub-watershed level. The main difference I observed is that using single watershed significantly reduced the upper value of “avoided export” and “sediment deposition” as compared to that of using sub-watershed. The value of other output is nearly the same, although the upper value of “sediment export” and “usle” were slightly smaller when using sub-watersheds. The difference I saw is on the values, no aggregation was found.
Many thanks for your time !!

4

When you use sub-watersheds, what is shown in the output watershed_results_sdr.shp? It should list all of the sub-watersheds, with values for each one. If this isn’t happening, can you post a screenshot of your sub-watershed table and watershed_results_sdr.shp table?

~ Stacie

5

Thank you for your straightforward solution. The shape file aggregated values for each subwatershed, just like zonal statistics. Thank you very much

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