The Watershed tool determines the contributing area above a set of cells in a raster.
Note:
To run this tool, the portal must be configured for raster analysis.
If you do not see this tool in Map Viewer, contact your portal administrator. Your portal may not be configured for raster analysis, or you may not have the privileges required to run the tool.
Workflow diagram
Examples
An input point on the Mississippi River in Louisiana will create a watershed feature extending to include areas from New York to Montana and into Canada.
Usage notes
A watershed is the upslope area that contributes flow—generally water—to a common outlet as concentrated drainage. It can be part of a larger watershed and can also contain smaller watersheds, called subbasins.
The value of each watershed will be taken from the value of the source in the input raster or feature pour point layer. When the pour point is a raster dataset, the cell values are used by default. When the pour point is a point feature dataset, the values will come from the specified field.
The Watershed tool only supports a D8 input flow direction raster layer.
When specifying the input pour point locations as feature data, the default field will be the first available valid field. If no valid fields exist, the ObjectID field (for example, OID or FID) will be the default.
The parameters for this tool are listed in the following table:
| Parameter | Explanation |
|---|---|
| Choose flow direction layer | The input raster that shows the direction of flow out of each cell. The flow direction raster can be created using the Flow Direction raster function, with default flow direction type D8. |
| Specify input pour point locations | The input pour point locations. This can be a raster or a point feature. For a raster, this represents cells above which the contributing area, or catchment, will be determined. All cells that are not NoData will be used as source cells. For a point input, this represents locations above which the contributing area, or catchment, will be determined. |
| Choose pour point field | The field used to assign values to the pour point locations. If the input pour point layer is a raster, Value is used. If it is feature, a numeric field is used. If the field contains floating-point values, they will be truncated into integers. |
| Result layer name | The name of the layer that will be created in My Content and added to the map. The default name is based on the tool name and the input layer name. If the layer already exists, you will be prompted to provide another name. You can specify the name of a folder in My Content where the result will be saved using the Save result in drop-down box. |
Environments
Analysis environment settings are additional parameters that affect a tool's results. You can access the tool's analysis environment settings by clicking the gear icon 
at the top of the tool pane.
This tool honors the following Analysis Environments:
- Output coordinate system—Specifies the coordinate system of the output layer.
- Extent—Specifies the area to be used for analysis.
- Snap Raster—Adjusts the extent of the output so it matches the cell alignment of the specified snap raster layer.
- Cell size—The cell size to use in the output layer.
- Mask—Specifies a mask layer, where only the cells that fall within the mask area will be used for analysis.
Similar tools and raster functions
Use the Watershed tool to determine the contributing area above a set of cells in a raster. Other tools may be useful in solving similar problems.
Map Viewer analysis tools and raster functions
Use the Watershed raster function to determine the contributing area above a set of cells in a raster.
ArcGIS Pro analysis tools and raster functions
The Watershed geoprocessing tool is available in the Spatial Analyst toolbox.
The Watershed tool is also available as a Raster Analysis toolbox.
Watershed is also available as a raster function.
ArcGIS Enterprise developer resources
If you are working in the ArcGIS REST API, use the Watershed task.
If you are working in ArcGIS API for Python, use watershed 
from the arcgis.raster.functions.gbl module.