These functions help you use hydrology analysis.
trace_downstream
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arcgis.features.hydrology.trace_downstream(input_points, point_id_field=None, source_database='Finest', generalize=False, gis=None, future=False) 
The
trace_downstreammethod delineates the downstream path from a specified location. Esri-curated elevation data is used to create an output polyline delineating the flow path downstream from the specified input location. This method accesses a service using multiple source databases which are available for different geographic areas and at different spatial scales.Parameter
Description
input_points
Required FeatureSet or Spatially Enabled DataFrame Points delineating the starting location to calculate the downstream location from. See Feature Input.
point_id_field
Optional string. Field used to identify the feature from the source data. This is useful for relating the results back to the original source data.
source_database
Optional string. Keyword indicating the source data that will be used in the analysis. This keyword is an approximation of the spatial resolution of the digital elevation model used to build the foundation hydrologic database. Since many elevation sources are distributed with units of arc seconds, this keyword is an approximation in meters for easier understanding.
Finest: Finest resolution available at each location from all possible data sources.
10m: The hydrologic source was built from 1/3 arc second - approximately 10 meter resolution, elevation data.
30m: The hydrologic source was built from 1 arc second - approximately 30 meter resolution, elevation data.
90m: The hydrologic source was built from 3 arc second - approximately 90 meter resolution, elevation data.
The default value is ‘Finest’.
generalize
Optional boolean. Determines if the output downstream trace lines will be smoothed into simpler lines.
The default value is False.
gis
Optional
GISObject instance. If not provided as input, a GIS object instance logged into an active portal with elevation helper services defined must already be created in the active Python session. A GIS object instance can also be optionally explicitly passed in through this parameter.future
Optional boolean. If True, a future object will be returned and the process will not wait for the task to complete. The default is False, which means wait for results.
- Returns
A new
FeatureSet
# USAGE EXAMPLE: To trace downstream path from from the outlet points. path = trace_downstream(input_points=fs, source_database='Finest', generalize=False)
watershed
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arcgis.features.hydrology.watershed(input_points, point_id_field=None, snap_distance=10, snap_distance_units='Meters', source_database='Finest', generalize=False, gis=None, return_snapped_points=True, future=False) 
The
watershedis used to identify catchment areas based on a particular location you provide and ArcGIS Online Elevation data.Parameter
Description
input_points
Required FeatureSet or Spatially Enabled DataFrame. Points delineating the starting location to calculate the downstream location from. See Feature Input.
point_id_field
Optional String. Field used to identify the feature from the source data. This is useful for relating the results back to the original source data.
snap_distance
Optional float. The maximum distance to move the location of an input point.
Interactive input points and documented gage locations may not exactly align with the stream location in the DEM. This parameter allows the task to move the point to a nearby location with the largest contributing area.
The snap distance should always be larger than the source data resolution. By default, the snapping distance is calculated as the resolution of the source data multiplied by 5.
The default value is 10.
snap_distance_units
Optional String. The linear units specified for the snap distance.
Choice list: [‘Meters’, ‘Kilometers’, ‘Feet’, ‘Yards’, ‘Miles’].
The default value is ‘Meters’.
source_database
Optional String. Keyword indicating the source data that will be used in the analysis. This keyword is an approximation of the spatial resolution of the digital elevation model used to build the foundation hydrologic database. Since many elevation sources are distributed with units of arc seconds, this keyword is an approximation in meters for easier understanding.
Finest: Finest resolution available at each location from all possible data sources.10m: The hydrologic source was built from 1/3 arc second - approximately 10 meter resolution, elevation data.30m: The hydrologic source was built from 1 arc second - approximately 30 meter resolution, elevation data.90m: The hydrologic source was built from 3 arc second - approximately 90 meter resolution, elevation data.
The default value is ‘Finest’.
generalize
Optional boolean. Determines if the output downstream trace lines will be smoothed into simpler lines.
The default value is False.
gis
Optional
GISObject instance. If not provided as input, a GIS object instance logged into an active portal with elevation helper services defined must already be created in the active Python session. A GIS object instance can also be optionally explicitly passed in through this parameter.return_snapped_points
Optional boolean. Determines if a point feature at the watershed’s pour point will be returned. If snapping is enabled, this might not be the same as the input point.
The default value is True.
future
Optional boolean. If True, a future object will be returned and the process will not wait for the task to complete. The default is False, which means wait for results.
- Returns
Result object comprised of two FeatureSets - one for watershed_area, and another for snapped_points
# USAGE EXAMPLE: To identify catchment areas around Chennai lakes. lakes_watershed = watershed(input_points=lakes_fs, snap_distance=10, snap_distance_units='Meters', source_database='Finest', generalize=False)