Minimum Size of subbasin

[Hassen Mohammed]

Dear ArcSWAT Google Group Members,
I am processing a million hectare size watershed to simulate daily stream-flow and sed-yield. I am using a 30 m DEM and  ArcSWAT 2012. I want to limit the number of sub-basins by giving an area threshold during the initial stream network and subbasin outlets definition step. The threshold area I entered was 500 ha, which is much lower than the default minimum threshold   area. The problem is the creation of more than 2500 watersheds  with an area of less than the threshold area,500 ha I input, smaller in size, starting from 0.09 ha (30 m X 30 m). I cant merge sub-watersheds in ArcSWAT. These so many number of slivers make my analyses more difficult. How can limit watershed creation < 500 ha? In which step can I do this? Please help. Thank you so much.

Hassen Mohammed

[Chris George]

The threshold for subbasin areas is really a threshold on the area
required to form a stream, so it only directly affects outer subbasins -
ones in which streams start. You get small internal subbasins where
stream junctions occur close together.

QSWAT is an alternative to ArcSWAT, using QGIS instead of ArcGIS. It
has an option to automatically merge small subbasins with their
downstream subbasins, where you select 'small' in terms of either area
in hectares or percentage of mean subbasin size.

QSWAT is available from the SWAT web site, at
http://swat.tamu.edu/software/qswat/

Chris

> --
> You received this message because you are subscribed to the Google
> Groups "ArcSWAT" group.
> To unsubscribe from this group and stop receiving emails from it, send
> an email to arcswat+u...@googlegroups.com
> <mailto:arcswat+u...@googlegroups.com>.
> To post to this group, send email to arc...@googlegroups.com
> <mailto:arc...@googlegroups.com>.
> Visit this group at https://groups.google.com/group/arcswat.
> For more options, visit https://groups.google.com/d/optout.