Re: [GRASS-user] r.watershed identify inland watershed

[ming han]

Hi Micha

I understand what you mean. But it requires another step to
manually identify depressions from these pre-conditioned DEM.

Cheers
Ming


Micha Silver  于2021年4月3日周六 下午12:43写道：

>
> On 4/2/21 5:37 PM, ming han wrote:
> > Maybe I am the only one who has this demand. Following is just a
> > recommendation to GRASS r.watershed function.
> > Maybe it is worth having an option to avoid r.watershed overcome
> > depressions.
> > The reasons are 1) there are many hydrologically pre condition DEM
> > data available globally, such as:HydroSHEDS, MERIT
> > 2) the depression in these DEM are real
> > depressions, overcome these depressions will make the entire drainage
> > system
>
>
> Regarding Hydrosheds, the documentation[1] in section 3.4 explains how
> they overcame the problem of sinks. They performed a regular "fill
> sinks" operation on areas that were SRTM artifacts. True natural
> depressions were identified manually, then another manual procedure of
> carving rivers was done to force flow thru these depressions and produce
> hydrologically correct streams and basins. So pre-conditioning to
> overcome depressions is not a magic bullet...
>
>
> In my opinion, the best results are obtained when true depressions
> (pits, salt playas or karst regions) are identified, and set to NULL in
> the elevation raster. That will allow r.watershed to stop routing at
> those locations, and produce correct stream and basin layers.
>
>
> [1]https://hydrosheds.org/images/inpages/HydroSHEDS_TechDoc_v1_2.pdf
>
>
> > incorrectly.
> >
> > I understand GRASS has other functions to solve this problem, but just
> > a user recommendation. I use GRASS a lot.
> >
> > Thanks
> > Ming
> >
> > ming han mailto:dustm...@gmail.com>>
> > 于2021年3月30日周二 上午8:06写道：
> >
> > Got it, thanks everyone~
> > Ming
> >
> > Micha Silver mailto:tsvi...@gmail.com>>
> > 于2021年3月29日周一 下午2:40写道：
> >
> > Hello:
> >
> > You might try `r.param.scale`, or even better `r.geomorphons`
> > modules to
> > identify geomorphology features, then filter out all pixels
> > identified
> > as pits.
> >
> >
> > r.watershed is purposely designed to overcome depressions, and
> > find flow
> > routing thru these spots. So I don't think you can use that
> > module to
> > identify depressions.
> >
> >
> > On 3/27/21 8:49 PM, ming han wrote:
> > > Hi  Everyone
> > >
> > >  When I do watershed delineation using r.watershed for
> > great salt
> > > lake watershed. I found r.watershed always tried to assign
> > an outlet
> > > for a great salt lake, which does actually not exist because
> > it is an
> > > inland lake and the great salt lake has no watershed outlet
> > at all.
> > >
> > >   I noticed that there is a depression option. But is
> > there any
> > > way that  r.watershed can automatically identify depressions
> > while
> > > defining flow accumulation and stream network?
> > >
> > > Thanks
> > > Ming
> > >
> > > ___
> > > grass-user mailing list
> > > grass-user@lists.osgeo.org 
> > > https://lists.osgeo.org/mailman/listinfo/grass-user
> > 
> >
> > --
> > Micha Silver
> > Ben Gurion Univ.
> > Sde Boker, Remote Sensing Lab
> > cell: +972-523-665918
> >
> --
> Micha Silver
> Ben Gurion Univ.
> Sde Boker, Remote Sensing Lab
> cell: +972-523-665918
>
>
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Re: [GRASS-user] r.watershed identify inland watershed

[Micha Silver]

On 4/2/21 5:37 PM, ming han wrote:
Maybe I am the only one who has this demand. Following is just a 
recommendation to GRASS r.watershed function.
Maybe it is worth having an option to avoid r.watershed overcome 
depressions.
The reasons are 1) there are many hydrologically pre condition DEM 
data available globally, such as:HydroSHEDS, MERIT
                            2) the depression in these DEM are real 
depressions, overcome these depressions will make the entire drainage 
system



Regarding Hydrosheds, the documentation[1] in section 3.4 explains how 
they overcame the problem of sinks. They performed a regular "fill 
sinks" operation on areas that were SRTM artifacts. True natural 
depressions were identified manually, then another manual procedure of 
carving rivers was done to force flow thru these depressions and produce 
hydrologically correct streams and basins. So pre-conditioning to 
overcome depressions is not a magic bullet...



In my opinion, the best results are obtained when true depressions 
(pits, salt playas or karst regions) are identified, and set to NULL in 
the elevation raster. That will allow r.watershed to stop routing at 
those locations, and produce correct stream and basin layers.



[1]https://hydrosheds.org/images/inpages/HydroSHEDS_TechDoc_v1_2.pdf



incorrectly.

I understand GRASS has other functions to solve this problem, but just 
a user recommendation. I use GRASS a lot.


Thanks
Ming

ming han mailto:dustm...@gmail.com>> 
于2021年3月30日周二 上午8:06写道：


Got it, thanks everyone~
Ming

Micha Silver mailto:tsvi...@gmail.com>>
于2021年3月29日周一 下午2:40写道：

Hello:

You might try `r.param.scale`, or even better `r.geomorphons`
modules to
identify geomorphology features, then filter out all pixels
identified
as pits.


r.watershed is purposely designed to overcome depressions, and
find flow
routing thru these spots. So I don't think you can use that
module to
identify depressions.


On 3/27/21 8:49 PM, ming han wrote:
> Hi  Everyone
>
>      When I do watershed delineation using r.watershed for
great salt
> lake watershed. I found r.watershed always tried to assign
an outlet
> for a great salt lake, which does actually not exist because
it is an
> inland lake and the great salt lake has no watershed outlet
at all.
>
>       I noticed that there is a depression option. But is
there any
> way that  r.watershed can automatically identify depressions
while
> defining flow accumulation and stream network?
>
> Thanks
> Ming
>
> ___
> grass-user mailing list
> grass-user@lists.osgeo.org 
> https://lists.osgeo.org/mailman/listinfo/grass-user


-- 
Micha Silver

Ben Gurion Univ.
Sde Boker, Remote Sensing Lab
cell: +972-523-665918


--
Micha Silver
Ben Gurion Univ.
Sde Boker, Remote Sensing Lab
cell: +972-523-665918

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Re: [GRASS-user] r.watershed identify inland watershed

[Veronica Andreo]

Dear Ming,

To avoid that your suggestion gets lost in emails, please fill in a
*feature request* issue with all details here:
https://github.com/OSGeo/grass/issues/new/choose

Best,
Vero


El vie, 2 abr 2021 a las 16:37, ming han () escribió:

> Maybe I am the only one who has this demand. Following is just a
> recommendation to GRASS r.watershed function.
> Maybe it is worth having an option to avoid r.watershed overcome
> depressions.
> The reasons are 1) there are many hydrologically pre condition DEM data
> available globally, such as:HydroSHEDS, MERIT
> 2) the depression in these DEM are real
> depressions, overcome these depressions will make the entire drainage
> system incorrectly.
>
> I understand GRASS has other functions to solve this problem, but just a
> user recommendation. I use GRASS a lot.
>
> Thanks
> Ming
>
> ming han  于2021年3月30日周二 上午8:06写道：
>
>> Got it, thanks everyone~
>> Ming
>>
>> Micha Silver  于2021年3月29日周一 下午2:40写道：
>>
>>> Hello:
>>>
>>> You might try `r.param.scale`, or even better `r.geomorphons` modules to
>>> identify geomorphology features, then filter out all pixels identified
>>> as pits.
>>>
>>>
>>> r.watershed is purposely designed to overcome depressions, and find flow
>>> routing thru these spots. So I don't think you can use that module to
>>> identify depressions.
>>>
>>>
>>> On 3/27/21 8:49 PM, ming han wrote:
>>> > Hi  Everyone
>>> >
>>> >  When I do watershed delineation using r.watershed for great salt
>>> > lake watershed. I found r.watershed always tried to assign an outlet
>>> > for a great salt lake, which does actually not exist because it is an
>>> > inland lake and the great salt lake has no watershed outlet at all.
>>> >
>>> >   I noticed that there is a depression option. But is there any
>>> > way that  r.watershed can automatically identify depressions while
>>> > defining flow accumulation and stream network?
>>> >
>>> > Thanks
>>> > Ming
>>> >
>>> > ___
>>> > grass-user mailing list
>>> > grass-user@lists.osgeo.org
>>> > https://lists.osgeo.org/mailman/listinfo/grass-user
>>>
>>> --
>>> Micha Silver
>>> Ben Gurion Univ.
>>> Sde Boker, Remote Sensing Lab
>>> cell: +972-523-665918
>>>
>>> ___
> grass-user mailing list
> grass-user@lists.osgeo.org
> https://lists.osgeo.org/mailman/listinfo/grass-user
>
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Re: [GRASS-user] r.watershed identify inland watershed

[ming han]

Maybe I am the only one who has this demand. Following is just a
recommendation to GRASS r.watershed function.
Maybe it is worth having an option to avoid r.watershed overcome
depressions.
The reasons are 1) there are many hydrologically pre condition DEM data
available globally, such as:HydroSHEDS, MERIT
2) the depression in these DEM are real
depressions, overcome these depressions will make the entire drainage
system incorrectly.

I understand GRASS has other functions to solve this problem, but just a
user recommendation. I use GRASS a lot.

Thanks
Ming

ming han  于2021年3月30日周二 上午8:06写道：

> Got it, thanks everyone~
> Ming
>
> Micha Silver  于2021年3月29日周一 下午2:40写道：
>
>> Hello:
>>
>> You might try `r.param.scale`, or even better `r.geomorphons` modules to
>> identify geomorphology features, then filter out all pixels identified
>> as pits.
>>
>>
>> r.watershed is purposely designed to overcome depressions, and find flow
>> routing thru these spots. So I don't think you can use that module to
>> identify depressions.
>>
>>
>> On 3/27/21 8:49 PM, ming han wrote:
>> > Hi  Everyone
>> >
>> >  When I do watershed delineation using r.watershed for great salt
>> > lake watershed. I found r.watershed always tried to assign an outlet
>> > for a great salt lake, which does actually not exist because it is an
>> > inland lake and the great salt lake has no watershed outlet at all.
>> >
>> >   I noticed that there is a depression option. But is there any
>> > way that  r.watershed can automatically identify depressions while
>> > defining flow accumulation and stream network?
>> >
>> > Thanks
>> > Ming
>> >
>> > ___
>> > grass-user mailing list
>> > grass-user@lists.osgeo.org
>> > https://lists.osgeo.org/mailman/listinfo/grass-user
>>
>> --
>> Micha Silver
>> Ben Gurion Univ.
>> Sde Boker, Remote Sensing Lab
>> cell: +972-523-665918
>>
>>
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Re: [GRASS-user] r.watershed identify inland watershed

[ming han]

Got it, thanks everyone~
Ming

Micha Silver  于2021年3月29日周一 下午2:40写道：

> Hello:
>
> You might try `r.param.scale`, or even better `r.geomorphons` modules to
> identify geomorphology features, then filter out all pixels identified
> as pits.
>
>
> r.watershed is purposely designed to overcome depressions, and find flow
> routing thru these spots. So I don't think you can use that module to
> identify depressions.
>
>
> On 3/27/21 8:49 PM, ming han wrote:
> > Hi  Everyone
> >
> >  When I do watershed delineation using r.watershed for great salt
> > lake watershed. I found r.watershed always tried to assign an outlet
> > for a great salt lake, which does actually not exist because it is an
> > inland lake and the great salt lake has no watershed outlet at all.
> >
> >   I noticed that there is a depression option. But is there any
> > way that  r.watershed can automatically identify depressions while
> > defining flow accumulation and stream network?
> >
> > Thanks
> > Ming
> >
> > ___
> > grass-user mailing list
> > grass-user@lists.osgeo.org
> > https://lists.osgeo.org/mailman/listinfo/grass-user
>
> --
> Micha Silver
> Ben Gurion Univ.
> Sde Boker, Remote Sensing Lab
> cell: +972-523-665918
>
>
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Re: [GRASS-user] r.watershed identify inland watershed

[Ken Mankoff]

I'm on mobile and can't fully reply, but isn't there an r.lakes or r.fill
module (possibly add on) that does this?

Generic answer: r.watershed is the wrong tool, but GRASS has support for
this.

Please excuse brevity. Sent from tiny pocket computer with non-haptic
feedback keyboard.

On Mon, Mar 29, 2021, 11:40 Micha Silver  wrote:

> Hello:
>
> You might try `r.param.scale`, or even better `r.geomorphons` modules to
> identify geomorphology features, then filter out all pixels identified
> as pits.
>
>
> r.watershed is purposely designed to overcome depressions, and find flow
> routing thru these spots. So I don't think you can use that module to
> identify depressions.
>
>
> On 3/27/21 8:49 PM, ming han wrote:
> > Hi  Everyone
> >
> >  When I do watershed delineation using r.watershed for great salt
> > lake watershed. I found r.watershed always tried to assign an outlet
> > for a great salt lake, which does actually not exist because it is an
> > inland lake and the great salt lake has no watershed outlet at all.
> >
> >   I noticed that there is a depression option. But is there any
> > way that  r.watershed can automatically identify depressions while
> > defining flow accumulation and stream network?
> >
> > Thanks
> > Ming
> >
> > ___
> > grass-user mailing list
> > grass-user@lists.osgeo.org
> > https://lists.osgeo.org/mailman/listinfo/grass-user
>
> --
> Micha Silver
> Ben Gurion Univ.
> Sde Boker, Remote Sensing Lab
> cell: +972-523-665918
>
> ___
> grass-user mailing list
> grass-user@lists.osgeo.org
> https://lists.osgeo.org/mailman/listinfo/grass-user
>
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Re: [GRASS-user] r.watershed identify inland watershed

[Micha Silver]

Hello:

You might try `r.param.scale`, or even better `r.geomorphons` modules to 
identify geomorphology features, then filter out all pixels identified 
as pits.



r.watershed is purposely designed to overcome depressions, and find flow 
routing thru these spots. So I don't think you can use that module to 
identify depressions.



On 3/27/21 8:49 PM, ming han wrote:

Hi  Everyone

     When I do watershed delineation using r.watershed for great salt 
lake watershed. I found r.watershed always tried to assign an outlet 
for a great salt lake, which does actually not exist because it is an 
inland lake and the great salt lake has no watershed outlet at all.


      I noticed that there is a depression option. But is there any 
way that  r.watershed can automatically identify depressions while 
defining flow accumulation and stream network?


Thanks
Ming

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--
Micha Silver
Ben Gurion Univ.
Sde Boker, Remote Sensing Lab
cell: +972-523-665918

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