The Hydro Addressing Engine is a set of National Map geospatial REST service end points that allow software developers to address (or reference, index, or conflate) point, line or polygon features to the National Hydrography Dataset (NHD).

Data addressed to the NHD has a network address—a unique location on the NHD network. Features addressed to the NHD can represent nearly any kind water-related feature, such as biological sampling locations, stream gages, fish passage barriers, toxic spills, scenic or impaired stretches of river, or algal blooms on reservoirs.

This document lists the service end points, describes the input parameters, and includes example JSON requests and response objects.

The Addressing Engine is robust enough to allow development of web-based applications. For instance, the USGS HydroAdd tool, a flexible web-based addressing tool for the NHD, uses the Hydro Addressing Engine.

To learn more, contact us at hydroadd@usgs.gov