NAME

       r.water.outlet  - Creates watershed basins from a drainage direction map.

KEYWORDS

       raster, hydrology, watershed

SYNOPSIS

       r.water.outlet
       r.water.outlet --help
       r.water.outlet   input=name  output=name  coordinates=east,north   [--overwrite]   [--help]   [--verbose]
       [--quiet]  [--ui]

   Flags:
       --overwrite
           Allow output files to overwrite existing files

       --help
           Print usage summary

       --verbose
           Verbose module output

       --quiet
           Quiet module output

       --ui
           Force launching GUI dialog

   Parameters:
       input=name [required]
           Name of input drainage direction map

       output=name [required]
           Name for output watershed basin map

       coordinates=east,north [required]
           Coordinates of outlet point

DESCRIPTION

       r.water.outlet generates a watershed basin from a  drainage  direction  map  and  a  set  of  coordinates
       representing the outlet point of watershed.

       Input drainage direction map indicates the "aspect" for each cell. Multiplying positive values by 45 will
       give  the direction in degrees that the surface runoff will travel from that cell. The value -1 indicates
       that the cell is a depression area. Other negative values indicate that surface  runoff  is  leaving  the
       boundaries  of  the  current  geographic region. The absolute value of these negative cells indicates the
       direction of flow. This raster map is generated from r.watershed.

       Output raster map values of one (1) indicate the watershed basin. Values of  zero  (0)  are  not  in  the
       watershed basin.

NOTES

       In the context of this program, a watershed basin is the region upstream of an outlet point. Thus, if the
       user  chooses  an  outlet  point  on  a  hill  slope,  the  resulting  map  will be a thin silver of land
       representing the overland slope uphill of the point.

EXAMPLE

       A watershed in the North Carolina sample dataset region:
       g.region raster=elev_lid792_1m -p
       # the watershed outlet position should be placed on a stream (from
       # accumulation map):
       r.watershed elev_lid792_1m threshold=5000 accumulation=accum_5K drainage=draindir_5K basin=basin_5K
       r.water.outlet input=draindir_5K output=basin_A30 coordinates=638740.423248,220271.519225
       d.mon wx0
       d.rast map=accum_5K
       d.rast map=basin_A30
       # overlay with transparency
       r.colors map=basin_A30 color=grey
       d.his h=accum_5K i=basin_A30
       # report outlet size in ha
       r.report map=basin_A30 units=h

       Figure: Watershed draped over flow accumulation

SEE ALSO

        r.wateroutlet.lessmem (addon), d.where, r.basins.fill, r.watershed, r.topidx

AUTHOR

       Charles Ehlschlaeger, U.S. Army Construction Engineering Research Laboratory

SOURCE CODE

       Available at: r.water.outlet source code (history)

       Accessed: Friday Apr 04 01:19:47 2025

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       © 2003-2025 GRASS Development Team, GRASS GIS 8.4.1 Reference Manual

GRASS 8.4.1                                                                               r.water.outlet(1grass)