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 thresh=5000 accum=accum_5K drain=draindir_5K output=basin_5K
       r.water.outlet input=draindir_5K output=basin_A30 coord=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

       Figure: Watershed draped over flow accumulation

SEE ALSO

        d.where, r.basins.fill, r.watershed, r.topidx

AUTHOR

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

       Last changed: $Date: 2014-12-19 22:55:37 +0100 (Fri, 19 Dec 2014) $

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