U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2009–3054

Revised March 2010

The National Map—Hydrography

Printed on recycled paper

Using the Data

These data are designed to be used in general mapping 

and in the analysis of surface-water systems using geographic information system (GIS) technology. In mapping, 

the NHD is used with other data themes such as elevation, 

boundaries, and transportation to produce general reference 

maps. These maps often serve as base maps for special purpose mapping. A geologic map, for example, may show base 

map information such as hydrography as a reference.

In the analysis of surface water, scientists use the NHD 

and WBD by applying GIS technology. This takes advantage 

of a rich set of embedded attributes that can be processed by 

a computer system to generate specialized information. This 

information then can be portrayed in customized maps to better understand the results. These analyses of hydrography are 

possible largely because the NHD contains the flow-direction 

network, and uses an addressing system to link specific information about the water from other related databases such as 

water discharge, water quality, and fish population. Using the 

basic water features, flow network, linked information, and 

other characteristics, it is possible to study cause and effect 

relationships, such as how a source of poor water quality 

upstream might affect a fish population downstream. The 

WBD plays an important role in this analysis by outlining the 

Awosting Falls, New York. Photograph courtesy of Allen Karsh. area on the landscape that drains into the flow network defined 

The National Hydrography Dataset

The National Hydrography Dataset (NHD) is the 

surface-water component of The National Map. The 

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. Polygons are used to 

represent area features such as lakes, ponds, and rivers; 

lines are used to represent linear features such as streams 

and smaller rivers; and points are used to represent point 

features such as streamgages and dams. Lines also are 

used to show the water flow through area features such 

as the flow of water through a lake. The combination of 

lines is used to create a network of water and transported 

material flow to allow users of the data to trace movement 

in downstream and upstream directions.

The Watershed Boundary Dataset

The Watershed Boundary Dataset (WBD) is a 

companion dataset to the NHD. It defines the perimeter 

of drainage areas formed by the terrain and other landscape 

characteristics. The drainage areas are nested within each 

other so that a large drainage area, such as the Upper Mississippi River, will be composed of multiple smaller drainage 

areas such as the Wisconsin River. Each of these smaller areas 

can further be subdivided into smaller and smaller drainage 

areas. The WBD uses six different levels in this hierarchy, 

with the smallest averaging about 30,000 acres. The WBD is 

made up of polygons nested into the six levels of data.

Example of features in the National Hydrography Dataset over Dillon, 

Colorado.
by the NHD. These data also are linked to the Geographic 

Names Information System to provide accurate hydrography 

names. The NHD and WBD often are used as a data source 

to specific applications such as StreamStats, ICWater, or 

ArcHydro.

Data Availability

The NHD is available nationwide in two seamless datasets; 

one based on 1:24,000-scale topographic mapping, known as 

the high-resolution NHD, and the other based on 1:100,000-

scale topographic mapping, known as the medium-resolution 

NHD. It also is becoming available in select areas based on 

larger scales such as 1:5,000-scale mapping. The WBD also 

is available in a nationwide seamless dataset. Typically, users 

download the WBD polygons using either the fourth or sixth 

levels of the drainage hierarchy. The NHD and WBD will be 

available as part of the same database in 2010.

The NHD and WBD can be viewed in The National Map 

(http://nationalmap.gov/) and downloaded for use in a GIS. 

The NHD and WBD also can be downloaded from a specialized hydrography portal to address the specific needs of 

scientists (http://nhd.usgs.gov/). For data management purposes, the NHD is distributed in units defined by the second 

or fourth levels of the WBD. The hydrography data also can 

be downloaded from the Natural Resource Conservation 

Service (http://datagateway.nrcs.usda.gov/).

Using integrated geospatial data and hydrologic modeling to predict streamflow. Line-width is proportional to modeled streamflow.

Using National Hydrography Dataset upstream navigation 

to predict how dams can act as barriers to invasive species 

migration.
The Hydrography Partnership

Both the NHD and WBD were created by joining the 

efforts of many Federal, State, and local agencies. These large 

and complex databases were built by pooling the funding and 

resources of many agencies into a single effort. This partnership effort also allowed the many agencies to standardize on 

a common design to save money and improve data interoperability. Another example of hydrography partnership efforts is 

the NHDPlus, which was developed by the U.S. Environmental 

Protection Agency in partnership with the U.S. Geological 

Survey (USGS) to extend the power of the NHD by integrating a number of geospatial data to calculate streamflow volume 

and stream velocity for each stream segment. This information 

assists scientists by simulating the amount of water flowing in 

a stream and the speed of its movement, and linking to factors 

such as dissolved or suspended constituents in the water. This is 

particularly useful when studying the affects of water pollution.

The Nation Needs The National Map

As one of the cornerstones of the U.S. 

Geological Survey’s (USGS) National 

Geospatial Program, The National Map is 

a collaborative effort among the USGS and 

other Federal, State, local, and Tribal partners 

to improve and deliver topographic information for the Nation. The National Map has 

many uses ranging from recreation to scientific 

analysis to emergency response. The National 

Map is easily accessible for display on the 

Web, as products and services, and as downloadable data. The geographic information 

available from The National Map includes 

orthoimagery (aerial photographs), elevation, 

geographic names, hydrography, boundaries, transportation, structures, and land cover. 

Other types of geographic information can be 

added within the viewer or brought in with 

The National Map data into a Geographic 

Information System to create specific types of 

maps or map views. 

The National Map is a significant 

contribution to the National Spatial Data 

Infrastructure (NSDI) and provides high quality, integrated geospatial data and improved 

products and services including new generation digital topographic maps. The National 

Map also is foundational to implementation of 

the Department of the Interior (DOI) Geospatial Modernization Blueprint and meeting the 

DOI mission. The National Map underpins 

the USGS Science Strategy, which is based 

on a systems approach to help address multifaceted issues, provide better understanding of 

earth processes, and evaluate broad causes and 

consequences of the use and management of 

natural resources. The National Map promotes 

interdisciplinary science by providing nationally consistent, trusted geospatial data, and 

establishing a consistent national geographic 

context.

Integrating dams and water diversions to the National 

Hydrography Dataset to study effects on streamflow at 

streamgages.

The integrated National Hydrography Dataset and Watershed 

Boundary Dataset to define streams and watersheds.
Data Stewardship

The NHD and WBD partnership is now turning its attention to a program of data stewardship to improve upon the existing NHD and WBD to keep it continuously up-to-date. This data stewardship activity is based on the input of an even larger 

partnership of organizations knowledgeable about the hydrography in their local area. They will have the tools and processes 

necessary to improve the NHD. This will assure that the data are accurate, current, and meet the objectives of users. The NHD 

and WBD include metadata that will track the history of the data as they are repeatedly updated with time.

Further Information

More information about The National Map is available at http://nationalmap.gov/.

For information on other USGS products and services, call 1-888-ASK-USGS or visit the general interest publications 

Web site on maps, imagery and publications at http://www.usgs.gov/pubprod/.

For additional information, visit the http://ask.usgs.gov/ Web site or the USGS home page at http://www.usgs.gov/.

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Rolla Publishing Service Center

The Blue River near Kremling, Colorado. Photograph courtesy of Ariel Bates.