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I am trying to perform an overland flow routing on a large area using r.sim.water in GRASS GIS. I've looked at other answers and made sure to set my computational region to the elevation raster I'm using which seems to be the first issue. I ran the following command:

r.sim.water -t elevin=ForGrass_ProjectRaster1 dxin=ValleyDX dyin=ValleyDY rain=rain manin=manning infil=infilt depth=depth --overwrite

The rain, infiltration, and manning maps were just made like in the tutorial as a trial step:

# synthetic maps
r.mapcalc "rain    = if(elevation.10m, 5.0, null())"
r.mapcalc "manning = if(elevation.10m, 0.05, null())"
r.mapcalc "infilt  = if(elevation.10m, 0.0, null())"

The result in the command window shows:

Number of threads: 1
default nwalk=401152772, rwalk=401152772.000000
Min elevation   = 326.00 m
Max elevation   = 5381.00 m
Mean Source Rate (rainf. excess or sediment)    = 0.000001 m/s or kg/m2s
Mean flow velocity  = 3.995791 m/s
Mean Mannings   = 0.095378
Number of iterations    = 159 cells
Time step   = 0.94 s
(Thu Jun 13 21:44:06 2019) Command finished (23 sec) 

And gives the following output:

enter image description here

So while it does not throw an error, the answer "converges" way too quickly for the size of my area and the 15m resolution. Anyone familiar with the command know what may be stopping the process without throwing an error?

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    I'm not familiar with r.sim.water, but do you have a raster map in your location called "elevation.10m"? If not, then all your synthetic maps will be null. You can test with i.e. r.info rain. – Micha Jun 14 at 19:58

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