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Questions tagged [r.watershed]

r.watershed is an R module that calculates hydrological parameters and RUSLE factors.

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Is it possible to split a polygon-subwatershed with a gage point without v.overlay?

After creating a clean map of subwatersheds I want to split some where control gages are located. If I try to do this with v.overlay (AND) - clipping subwatersheds previously generated with r.basins ...
Nikolay Yasinskiy's user avatar
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How to set up r.watersheds if it generates too short streams on river valley sections that are too wide

Related to this question too I am delineating a very big watershed with very wide river valley. When I tried to perform with PCRaster, the directions map wasn't generated properly, as sticks upon ...
Nikolay Yasinskiy's user avatar
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1 answer
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Running GRASS r.watershed in Python returns SyntaxError: expression cannot contain assignment

I am trying to run r.watershed in my Python script using GRASS. I am trying to put in the appropriate parameters but I keep getting the error: SyntaxError: expression cannot contain assignment, ...
gwydion93's user avatar
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r.watershed error in QGIS (3.16.2) for MAC [closed]

I'm trying to use the r.watershed tool, here is the error that is arising. I've tried changing the GRASS path to custom /Applications/QGIS.app/Contents/Resources/grass78 and it doesn't seem to work ...
Luna Paluna's user avatar
1 vote
0 answers
670 views

GRASS r.viewshed Command Line Error: Raster map <rasterfile> not found

I'm struggling to make sense of the grass command line syntax for specifying a raster geotif as an input parameter for a watershed analysis using a DEM tif. I may also have the user folder setup, ...
GIS_py's user avatar
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r.watershed stream/rivers pixel size

I am using r.watershed to get a stream map (which I assume is rivers). However the output rivers is always 1 pixel wide. I would've assumed that if I run this on say Iraq I would see the Tigris and ...
KaiserJohaan's user avatar
1 vote
1 answer
273 views

GRASS GIS change raster output size?

I have a large inut raster geotiff map of size 12000x9000. I am running r.watershed to output a stream raster map. However it is much lower resolution, only about 960x711. How do I make GRASS GIS / r....
KaiserJohaan's user avatar
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1k views

Why no need for "fill-sinks" when using r.watershed in GRASS QGIS?

I've seen a few places that when using the r.watershed function in GRASS QGIS, you do not need to use the "fill-sinks" procedure on the DEM before running the function. According to the ...
Simen's user avatar
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3 votes
2 answers
3k views

Obtain channel/stream network from a DEM in QGIS

This might sound like a basic question, but running SAGA's Strahler order won't do the job for me. The lengths of the streams look way too short and this is quite a mountainous area. The result makes ...
Sep's user avatar
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GRASS 7.8.3 problem with r.watershed and r.water.outlet

I need to find the basin of a small river and this is what I did: I found the drainage direction with r.watershed I used r.water.outlet to find the basin for the coordinates of the water outlet point....
Elena Aragona's user avatar
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Flow accumulation from r.watershed creates discontinuous stream network

I am interested in using r.watershed as integrated in QGIS for a course I teach, but am noticing discrepancies in the flow accumulation (facc) rasters and resulting stream networks that I get from ...
Trent Biggs's user avatar
1 vote
1 answer
257 views

how can interior basins be modified in the r.watershed GRASS function?

This is a follow up question to How does "Minimum Size of Exterior Watershed Basin" work in r.watershed command in qgis 2.18.12? I understood that the threshold parameter is used to ...
Juan Ossa's user avatar
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1 vote
0 answers
426 views

GRASS GIS: Getting know about stream power index (SPI) computation by r.watershed function

I need to know exact way how stream power index (SPI) is computed by module r.watershed. On the help page is that SPI is α * tan(β), where: α is cumulative upslope area draining through a point per ...
david_p's user avatar
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2 votes
1 answer
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Watershed Delineation Loop - r.water.outlet resulting in NAN area while snapped

I am attempting to create multiple watershed delineations for stations within a CSV file. I have files for flow direction (raster with a cell size of 30m), flow accumulation(raster with a cell size of ...
Nicole's user avatar
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3 votes
1 answer
3k views

How does "Minimum Size of Exterior Watershed Basin" work in r.watershed command in qgis 2.18.12?

I have delineated the watersheds from DEM using r.watershed command. I have specified the Minimum Size of Exterior Watershed Basin as 1500. I have read the description of r.watershed as well. I am not ...
Parth Gupta's user avatar
1 vote
1 answer
375 views

Getting error while executing grass algorithms from PyQGIS

I am trying to run r.water.outlet by PyQGIS but getting grass folder not configured error I have QGIS 2.18 installed and Grass is not installed on windows 10 and I am able to use r.water.outlet from ...
sudhanshud's user avatar
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1 answer
188 views

R.Watershed unable to process a large geotiff (dem) file

I have a large geotiff file (dem) that I am planning to use with r.watershed to delineate a very large drainage basin. The file is 142 GB. When I try to run r.watershed after a few second it gives me ...
Francis's user avatar
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3 votes
2 answers
2k views

Can't get GRASS r.water.outlet to work

I'm new to GRASS. We want to delineate a watershed using the LIDAR data we have our hands on. I tried to follow several procedures to do so, but despite all my efforts, I can only get it to select a ...
Horizen's user avatar
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1 vote
2 answers
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G_malloc error while running r.watershed in GRASS 7.0.4

I tried to use r.watershed function in GRASS GIS, and got an error message ERROR: G_malloc: unable to allocate 3837384596 bytes of memory at raster/r.watershed/ram/init_vars.c:146 before getting the ...
Heinz's user avatar
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