Data Exchange Description
This exchange enables participants to submit spatial representations of surface water related features. This exchange supplements water program related data flows that exchange surface water attribute information.
The NHDEvent data flow provides the means for States to submit the following data:
- spatial representations of surface water features
- surface water feature links to the underlying NHD features
- feature level spatial metadata
- linkage to the external surface water attributes (in the related data flow)
For more information about the concepts related to surface water features (events) visit the WATERS website.
Related Elements
- Associated Data Flows – The NHDEvent data flow is not a standalone data flow; in addition to the spatial data exchanged in this data flow, water program data must also be exchanged to provide information related to each spatial feature (such as water quality assessment information). The following data flows utilize the NHDEvent data flow to exchange the spatial data related to their program data:
- The National Hydrography Dataset (NHD) – The NHD is a comprehensive set of digital spatial data that contains information about surface water features, such as rivers and lakes. 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. The NHDEvent data flow 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.
- The EPA Reach Address Database (RAD) – The 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. For more information, see http://www.epa.gov/waters.
Project Summary and Future Directions
EPA recently made updates to the NHDEvent schema to support the new USGS V2.0 data model. These changes are reflected in the NHDEvent V2.0 schema and this schema version is expected to be stable for the foreseeable future.
Additional data flows are expected to make use of the NHDEvent data flow in the future to exchange their surface water related spatial data. As data flows adopt the NHDEvent data flow, they will be listed above in the Related Elements section.
Version Notes
Status: Supported
The NHDEvent documentation package has been received and reviewed by the NTG Conformance Committee. The Committee has deemed the schema and supporting flow documentation acceptable for use on the Exchange Network. The most recent version of the NHDEvent data exchange is version 2.0. The following links are to implementation resources for this most recent version.
For more information on the schema and documentation review, you can read the developer’s Schema Conformance Report above and the NTG’s Conformance Review. For additional information on the review process, please visit the section on Publishing a Data Exchange.
