Data Exchange Description
The National Hydrography Dataset Events (NHDEvent) data exchange enables participants to submit spatial representations of surface water-related features. It supplements water program-related data flows that exchange surface water attribute information. NHDEvent is not a standalone data flow; rather, it provides the means for Partners to submit:
- Spatial representations of surface water features;
- Surface water feature links to the underlying NHD features;
- Feature-level spatial metadata; and
- Linkage to the external surface water attributes (in the related data flow).
Information on EPA’s integrated information system for the nation’s surface waters is available at: Watershed Assessment, Tracking and Environmental Results (WATERS).
- Clean Water Act Integrated Reporting, Water Quality Assessment, Impaired Waters Data Exchange (OWIR) – In addition to the spatial data exchanged, water program data must also be exchanged to provide information related to each spatial feature (such as water quality assessment information). The OWIR data flow uses NHDEvent to exchange the spatial data related to the program data.
- National Hydrography Dataset (NHD) – USGS’ NHD is a comprehensive set of digital spatial data that represents the surface water of the United States using common features such as lakes, ponds, streams, rivers, canals, streamgages, and dams. The NHD provides a spatial framework for integrating water resources information, such as water quality assessments and impairments, gaging stations, and monitoring sites, by linking the information to the underlying NHD. NHDEvent will exchange data linked to any surface water base layer; however, as the surface water feature data component of The National Map, the NHD is the surface water base layer of choice.
- Reach Address Database (RAD) – EPA’s RAD contains a copy of the NHD and spatial representations of water-related activities, such as assessments and impairments, for many EPA Office of Water programs.
Project Summary and Future Directions
In March 2013, EPA updated the NHDEvent schema to v2.1 to support the USGS NHD v2.1 data model. Additional data flows are expected to make use of the NHDEvent data flow to exchange surface water-related spatial data.
The NHDEvent schema and documentation package has been approved for use on the Exchange Network. The most current version is v2.1.