An overview of the Hydrology toolset

Available with Spatial Analyst license.

The Hydrology tools are used to model the flow of water across a surface.

Information about the shape of the earth's surface is useful for many fields, such as regional planning, agriculture, and forestry. These fields require an understanding of how water flows across an area and how changes in that area may affect that flow.

When modeling the flow of water, you may want to know where the water came from and where it is going. The following topics explain how to use the hydrologic analysis functions to help model the movement of water across a surface, the concepts and key terms regarding drainage systems and surface processes, how the tools can be used to extract hydrologic information from a digital elevation model (DEM), and sample hydrologic analysis applications.

The Hydrology tools can be applied individually or used in sequence to create a stream network or delineate watersheds.



Creates a raster delineating all drainage basins.


Fills sinks in a surface raster to remove small imperfections in the data.

Flow Accumulation

Creates a raster of accumulated flow into each cell. A weight factor can optionally be applied.

Flow Direction

Creates a raster of flow direction from each cell to its downslope neighbor, or neighbors, using D8, Multiple Flow Direction (MFD) or D-Infinity (DINF) methods.

Flow Distance

Computes, for each cell, the horizontal or vertical component of downslope distance, following the flow path(s), to cell(s) on a stream into which they flow. In case of multiple flow paths, minimum, weighted mean, or maximum flow distance can be computed.

Flow Length

Calculates the upstream or downstream distance, or weighted distance, along the flow path for each cell.


Creates a raster identifying all sinks or areas of internal drainage.

Snap Pour Point

Snaps pour points to the cell of highest flow accumulation within a specified distance.

Stream Link

Assigns unique values to sections of a raster linear network between intersections.

Stream Order

Assigns a numeric order to segments of a raster representing branches of a linear network.

Stream to Feature

Converts a raster representing a linear network to features representing the linear network.


Determines the contributing area above a set of cells in a raster.

Tools in the Hydrology toolset

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