| Abstract: |
The National Hydrography Dataset (NHD) is the surface-water component of The National Map, an online interactive map that provides access to basic geographic information describing the landscape of the United States. The NHD is a comprehensive set of digital spatial data that represent surface-water features of the nation such as lakes, ponds, streams, rivers, canals, and oceans. These data are designed to be used in general mapping and in the analysis of surface water systems using a geographic information systems (GIS). NHD contains a rich set of embedded attributes that can be processed to generate specialized information largely possible because of a flow direction network that traces the water downstream or upstream. It also uses an addressing system to integrate specific information about the water such as water discharge, water quality, and fish community composition. Using the basic water features, flow network, linked information, and other characteristics, the user can study cause and effect relations, such as that between a point-source discharge as a source of poor water quality and the downstream health of a fish community. NHD has also been processed with elevation-derived data to be used in watershed analysis databases like StreamStats and NHDPlus. |