dear all,
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@PERMANENT flow=runoff threshold=100 accumulation=discharge basin=basin
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 that correct?
the resulting discharge-map using flow=runoff looks reasonable.
any help would be most appreciated!
thanks a lot and best regards, boris.