This page contains resources and information about USGS National Hydrography specifications. The National Map serves surface water data in several related geospatial datasets, including the National Hydrography Dataset (NHD), the Watershed Boundary Dataset (WBD), and the NHDPlus High Resolution (NHDPlus HR). For more information, please visit the National Hydrography webpage.
National Hydrography Dataset - General
The National Hydrography Dataset (NHD) standards are composed of a three primary references:
1) The Geographic Information Framework Data Content Standard, Part 6: Hydrography (FGDC-STD-014.6-2008) provides a conceptual framework for hydrography, but does not specifically define the NHD. The primary purpose of this part of the document is to support the exchange of surface water (hydrography) data, seeking to establish a common baseline for the semantic content of hydrography databases for public agencies and private enterprises. It also seeks to decrease the costs and simplify the exchange of hydrography data among local, Tribal, State, and Federal users and producers. That, in turn, discourages duplicative data collection. Benefits of adopting this part of the standard also include the long-term improvement of the geospatial hydrography data through the establishment of Web data services for hydrography data and maps within the community.
2) The NHD is an implementation of this standard, and is defined through a data model. The current data model is the National Hydrography Dataset (NHD) Model V2.3. The data model is a holistic view of the the entire NHD database, including an overview of the database structure, feature classes, event feature classes, attribute tables, domains, and feature-level metadata.
3) The Spec-X application, currently in a beta version, contains the most up-to-date data dictionary and feature descriptions for the NHD. Also available is the NHD User Guide containing the NHD Feature Catalog, which provides information on the structure, definitions, examples, and delineation guidelines of the NHD. Please note that the technology used for the NHD User Guild is now obsolete and we can no longer update the information within it. We are working to determine the best platform for this information. Please email email@example.com if you have questions.
Additionally, a draft version of Standards for National Hydrography Dataset (1999) is provided here as background information, but is not applicable to use as current NHD specification information.
Use of the National Hydrography Dataset Specifications
The NHD is a digital geospatial dataset. For it to be distributed, maintained, and updated from a national data repository, it must conform to a standardized structure, contain standardized values, hold only valid relationships, and represent only approved content. All operational phases are managed by customized software that enforce the standards, making it impossible to alter the national NHD database outside of this environment. All NHD datasets are “stamped” with a Version Number and a Schema Version (Model Identifier) found in the NHD Processing Parameters table associated with the data. The standards also contain judgment criteria that cannot be enforced by a software system. For example, a Lake/Pond may be incorrectly delineated and not conform to the standard outlined in the NHD Feature Catalog. These types of issues fall under the domain of quality assurance, using standards as a reference. Quality assurance is accomplished through training and controlled editing. The USGS has conducted hundreds of training seminars throughout the life of the NHD. In order to build or maintain NHD data, all editors must use an accredited set of tools that are only able to access after completion of an NHD training curriculum.
National Hydrography Dataset - Elevation-derived Hydrography
Elevation-Derived Hydrography is hydrography derived directly from elevation data, providing the best possible horizontal and vertical fit between they hydrography and the elevation data it was derived from. The USGS has published the Elevation-Derived Hydrography Acquisition Specifications and the Representation Extraction Attribution and Delineation Rules as guidance for delineating elevation-derived hydrographic features for the NHD.
NHDPlus High Resolution
NHDPlus High Resolution (NHDPlus HR) documentation includes a poster of the NHDPlus HR Data Model v1.0 with details on dataset structure, feature classes, domains, and relationships, and a User’s Guide for the National Hydrography Dataset Plus High Resolution.
Watershed Boundary Dataset
The Watershed Boundary Dataset (WBD) standards are published as Federal standards and procedures for the National Watershed Boundary Dataset (WBD), Techniques and Methods 11-A3. The current data model for the WBD is the Watershed Boundary Dataset (WBD) Data Model V2.3.