How to delineate watershed when one river has two outlet?

[Feiyan]

Hello Everyone !  

 I'm delineating watershed in QSWAT+. In my case, the river divides into two parts at the lower reaches. One  flows toword northeast, but the other one flows into a lake in the south. 

If I breaks the northern one like picture2, all of water from upper reaches will flow into the lake, this is not conform with reality. So how should I  delineate watershed？

Thank you and have a nice day!

[Chris George]

You can cut one channel as in your second picture. You should also
place an outlet point where the original junction was, which will ensure
you get a division into two of the channel through this point. Do the
delineation and create HRUs. Now look at the gis_routing table in the
project database. You will have stream A, say, flowing into point P
(the outlet point you created) flowing into channel B, say (which
ultimately flows into the lake). All you have to do is reduce the
percentage by which P flows into B from 100 to 40, for example, and add
a new flow from point P to the clipped channel with a percentage, in
this case, of 60.

You can, I expect, achieve the same changes in the SWAT+ editor, but I
am not familiar with that tool.

Chris

On 5/7/2021 2:13 PM, Feiyan wrote:
> Hello Everyone !
>  I'm delineating watershed in QSWAT+. In my case, the river divides
> into two parts at the lower reaches. One  flows toword northeast, but

> the other one flows into a lake in the south. picture2.png

> If I breaks the northern one like picture2, all of water from upper
> reaches will flow into the lake, this is not conform with reality. So

> how should I  delineate watershed？Picture2.png

> Thank you and have a nice day!
>

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[Feiyan]

@ Chris 

Thank you very much. I found the table you mentioned. I can change it in "......\Scenarios\Default\TxtInOut\chandeg.con" or the properties of channels in SWAT+Editor. Thanks for you help again.

Feiyan 

[Feiyan]

Chris，

Hello！I  meet an error in adding lakes when delineating watersheds. The lake in my study area is a closed lake, so I  created a  core shape and removed DEM with core(picture1). But after adding the lake shapefile and clicking the Ok, there is an error occurred(picture2). I tried to remove the lake core as picture3, the same error occured. Do you know why?