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I am using ArcMap 10.3 on a Windows x64 system.

I would like to extract the sub-watershed for a particular area. The data I used was ASTER 30m DEM and a shapefile of my study site. The first step was to clip the DEM using the shapefile of my study site.Then, the general steps included Fil, Flow Direction, Flow Accumulation, Basin. Figure 1 shows the sub-watershed, and there are 15 sub-watersheds I extracted.

Here what my concern is that the sub-watershed boundary is usually partial overlap the admistrative boundary. And the purpose of extracting the sub-watershed is to calculate the water yield in each sub-watershed. The mode I used to calculate the water yield is the InVEST water yield model. The accuracy of sub-watershed boundary can affect the results of water yield simulation.

So, I created a large-scale DEM mosaic dataset (Figure 1b) and then extract the watershed boundary from this big DEM mosaic dataset. I found, for example, that sub-watered No.1 in Figure 1a just account for a very small part in the watershed No.2 in Figure 1b. Here I am not sure that if I can use the sub-watershed boundary shown in Figure 1a to calculate the water yield in each sub-watershed in my study site.

How can I get better results?

enter image description here

  • 2
    Your watersheds must be based on larger dataset, not a clip. – FelixIP Nov 5 '17 at 20:29
  • Thank you @ FelixIP. First, I extracted the 1st level watersheds from the country. It was divided into 14 watersheds. Then, I used the big watershed (752 000 km²) where my study site is located to extract the 2nd level watersheds. – user121 Nov 6 '17 at 12:54
  • @FelixI, the new reaults indicated that the sub-watershed boundaries do not overlap the administrative boundary vell well. Many papers usually choose a whole watershed as the case study. But not always like this due to the different research objectives. Here, my new question is: is the value of water yield calculated on one part of a watershed a correct/useful value? Thank you. – user121 Nov 10 '17 at 2:26

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