[GRASS-user] question on r.watershed
boris.orlowsky at env.ethz.ch
Wed Nov 13 03:58:11 PST 2013
i have a question on the output of r.watershed.
my analysis goal is the following: from climate model output (from the
WATCH dataset, eu-watch.org), i have runoff on a 0.5 degree grid (entire
globe). i want to compute the accumulated flow for each grid cell,
taking the inflow from other grid cells into account. my idea is to use
r.watershed elevation=SRTM_1km at PERMANENT flow=runoff threshold=100
from grass gis (i have tried 6.4.1 and 7.0), using a MASK according to
the SRTM data.
i am a bit confused because the basin maps that i obtain differ strongly
between a run which includes the flow=runoff and a run without this
information. in the first case, catchments are lost over most of the
globe (random colors), without the flow=runoff i get the expected
basins. maybe i don't understand correctly what r.watershed is supposed
to do, but i thought that the basins should depend only on the dem. is
the resulting discharge-map using flow=runoff looks reasonable.
any help would be most appreciated!
thanks a lot and best regards, boris.
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