Presentation Abstract
	The National Hydrography Dataset (NHD)
	Hank Nelson, NHD, Data Stewardship Program, USGS, NGTOC II
	Thursday, September 11, 2008 - 10:50 AM - Track 3
	The National Hydrography Dataset (NHD) is the surface water component of The National Map, which provides the United States with access to basic geographic information that describes the landscape of the nation. The NHD is a comprehensive set of digital spatial data that represents the surface water using common features such as lakes, ponds, streams, rivers, canals, and oceans. This data is designed to be used in general mapping and in the analysis of surface water systems using geographic information systems. In mapping, the NHD is used with other themes of data such as elevation, boundaries, and transportation to produce general reference maps. In analysis, the NHD is used by scientists study surface water using geographic information system technology. This takes advantage of a rich set of embedded attributes that can be processed to generate specialized information largely possible because the NHD contains 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 population. Using the basic water features, flow network, linked information, and other characteristics, it is possible to study cause and affect relationships, such as how a source of poor water quality upstream might affect a fish population downstream.
	Presentation Powerpoint (63.1MB)