NGP Standards and Specifications

Hydrography Standards and Specifications

The National Map serves surface water hydrography data for the United States in several different datasets, including the National Hydrography Dataset (NHD) High Resolution, the Watershed Boundary Dataset (WBD), and the NHDPlus High Resolution (NHDPlus HR).  

Links to specifications tools and information can be found on this page. 

BETA - Spec-X

BETA - Spec-X

Spec-X is a guide for exploring The National Map Specifications. *BETA Release*

Spec-X BETA

NHD User Guide and Feature Catalog

NHD User Guide and Feature Catalog

The NHD User Guide contains Interactive tutorials, a feature catalog, and the NHD Video Library, which can be accessed by clicking on the "NHD User Guide" folder on the left side of the page.

NHD User Guide

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 V2.2.1. 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 NHD User Guide contains the NHD Feature Catalog, which provides structure, definitions, examples, and delineation guidelines for the NHD.  It is available in an interactive catalog of further definitions. To use it, click on NHD User Guide in the left panel, then Feature Catalog, then Hydrography Dataset. 

Additionally, a draft version of Standards for NHD from 1999 is available for research purposes only, 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. USGS is currently developing specifications and guidance for delineating hydrographic features for the NHD. A link will be provided here when they are available. 

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 and draft NHDPlus HR Data Dictionary

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