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nhd
National Hydrography Dataset
(NHD)
The National Hydrography Dataset (NHD) is a geographic
database that interconnects and uniquely identifies the
stream segments or "reaches" that comprise the nation's
surface water drainage system. It is based initially upon
the content of the U.S. Geological Survey 1:100,000-scale
Digital Line Graph (DLG) hydrography data integrated with
reach-related information from the U.S. Environmental Protection
Agency Reach File Version 3.0 (RF3). More specifically,
it contains reach codes for networked features and isolated
lakes, flow direction, names, stream level, and centerline
representations for areal water bodies.
The NHD provides a national framework for assigning reach
addresses to water-related entities, such as industrial
dischargers, drinking water supplies, fish habitat areas,
wild and scenic rivers. Reach addresses establish the locations
of these entities relative to one another within the NHD
surface water drainage network in a manner similar to street
addresses. Once linked to the NHD by their reach addresses,
the upstream/downstream relationships of these water-related
entities and any associated information about them can be
analyzed using software tools ranging from spreadsheets
to Geographic Information Systems (GIS). GIS can also be
used to combine NHD-based network analysis with other data
layers, such as soils, land use and population, to help
better understand and display their respective affects upon
one another. Furthermore, since the NHD provides a nationally
consistent framework for addressing and analysis, water-related
information linked to reach addresses by one organization
(national, state, local) can be shared with other organizations
and easily integrated into many different types of applications
to the benefit of all.
The National Hydrography Dataset is designed to provide
comprehensive coverage of hydrologic data for the US. While
initially based on 1:100,000-scale data, the NHD is designed
to incorporate -- and encourage the development of -- higher-resolution
data required by many users. It will facilitate the improved
integration of water-related data in support of the application
requirements of a growing national user community and will
enable shared maintenance and enhancement.
For more information on the National Hydrography Dataset,
see http://nhd.usgs.gov.
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