[GRASS-user] Re: understanding r.watershed

[Georg Kaspar]

> If these lakes have an outflow, i.e. water is leaving these lakes, the
> results will be more realistic when you omit the depression input to
> r.watershed and only use the (not filled) DEM.
> 
> If you are talking about the basins output having NULL values around
> these depression, this is because your basin threshold value was too
> high, set it to a lower value. Check the current flow accumulation
> output for a reasonable threshold.

so, my accumulation map contains values from -144714 to 58920 with a 
majority of cells between 0-100. what would be an appropriate threshold 
value? I already tried 5000 and it looked similar to the output I 
received from r.terraflow, but when running r.watershed with depression 
input I still receive those null()-areas...

by the way, this is what my region looks like:

GRASS 6.2.3 (Schweiz):~ > g.region -p
projection: 99 (Swiss. Obl. Mercator)
zone:       0
datum:      ch1903
ellipsoid:  bessel
north:      193996.9
south:      182009.4
west:       777510.9
east:       812479.6
nsres:      29.96875
ewres:      29.99030875
rows:       400
cols:       1166
cells:      466400