User:Jdsimley

National Hydrography Dataset

The National Hydrography Dataset (NHD) is the surface water component of The National Map for the United States. It is used to represent surface water on maps and is also used to perform geospatial analysis. The NHD is a digital vector dataset used by geographic information systems (GIS)for these two purposes. It contains features such as lakes, ponds, streams, rivers, canals, dams and streamgages. These data are designed to be used in general mapping and in the analysis of surface-water systems.

In mapping, the NHD is used with other data themes such as elevation, boundaries, and transportation to produce general reference maps. In geospatial analysis the NHD is used by scientists using GIS technology. This takes advantage of a rich set of attributes that can be processed to generate specialized information. These analyses are possible because the NHD contains a flow direction network that traces the water downstream or upstream. It also uses an addressing system to link specific information about the water 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 affect relations, such as how a source of poor water quality upstream might affect a fish population downstream.

Simley, J.D., Carswell Jr., W.J., 2009, The National Map—Hydrography: U.S. Geological Survey Fact Sheet 2009-3054, 4 p.