[GRASS-user] Global Hydrological modeling with r.watershed, r.stream.extract, r.stream.extract

[Giuseppe Amatulli]

Thanks Ken,
I try that option but it was creating output files (e.g. flow accumulation)
extremely huge, moreover it does not support the option  -b.
Markus any suggestion?
Thanks
Giuseppe

On Sun, 10 May 2020 at 19:57, Ken Mankoff <mankoff at gmail.com> wrote:

> Hi Guiseppe,
>
> I've successfully run with 4.5 billion cells. How many cells do you have?
> I notice you do not have the "-m" flag to tell it to use disk swap in place
> of all memory. Maybe that would help?
>
>   -k.
>
> On 2020-05-05 at 11:55 -07, Giuseppe Amatulli <giuseppe.amatulli at gmail.com>
> wrote...
> > Dear GRASS Team
> >
> > I am running a global analysis where I need to use "tiles" as
> computational
> > units in which I use the following three commands:
> > r.watershed -b elevation=elv depression=dep accumulation=flow
> > drainage=dir_rw flow=pixel_area  memory=100000 --o --verbose
> > r.stream.extract elevation=elv accumulation=flow depression=dep
> > threshold=0.05 direction=dir_rs stream_raster=stream memory=100000 --o
> > --verbose
> > r.stream.basins -l  stream_rast=stream direction=dir_rs   basins=lbasin
> >  memory=100000 --o --verbose
> >
> > The basins that were not completely within a tile (resulting in
> > broken-basins) have been removed (see below the three tiles in Figs.
> 1,2,3
> > including only entire basins),
> > and now I'm in the phase of merging all the tiles having only complete
> > basins.
> >
> > When I merge the tiles (Fig 4), some basin borders do not match
> perfectly,
> > and some areas have NoData (see Fig 5,6) or have the Basin ID of the
> below
> > basin (Fig 7).
> > I noticed that these phenomena appear only when I merge tiles that have
> > very large broken-basins that can not be included in the tile due to RAM
> > limitations.
> >
> > My thought is that r.stream.basins needs the entire dimension of two
> > adjacent basins to be able to detect the border without gap and without a
> > potential random selection.
> > Is there any part of the r.stream.basins code that I can potentially
> check
> > and eventually hack to avoid this problem?
> >
> > For the rest, all the RAM limitation and other problem have been solved
> > soon we will have a global stream network and basin delineation performed
> > 100% in GRASS!!!
> >
> > Thank you
> > Best Regards
> > Giuseppe
> >
> >
> >
> > Fig 1. Left Tile
> > [image: image.png]
> >
> >
> > Fig 2. Center tile
> > [image: image.png]
> >
> >
> > Fig 3. Right Tile
> > [image: image.png]
> >
> >
> > Fig 4. Merge all the tiles
> > [image: image.png]
> >
> >
> > Fig 5. Gap -> small white area
> > [image: image.png]
> >
> >
> > Fig 6. Gap -> small white area
> > [image: image.png]
> >
> > Fig 7. boarder Basins inconsistency among tiles
> >
> > [image: image.png]
>
>

-- 
Giuseppe Amatulli, Ph.D.

Research scientist at
School of Forestry & Environmental Studies
Center for Research Computing
Yale University
New Haven, CT, USA
06511
Teaching: http://spatial-ecology.net
Work:  https://environment.yale.edu/profile/giuseppe-amatulli/
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