The NHD is a comprehensive set of digital spatial data representing surface water of the United States and depicts common features such as rivers, streams, lakes, canals and oceans. The NHD is maintained by the US Geological Survey (USGS) and is the surface water component of The National Map.
The NHD is designed to be used in general mapping and in the analysis of surface water systems using GIS. This is possible due to a built-in flow network, allowing traces upstream and downstream from any point on a stream. It also uses a unique addressing system, called reach codes, allowing users to link specific information such as water quality or discharge rates.
Examples of water-related entities which can be referenced to the NHD are industrial discharges, fish habitat, wild rivers and water quality assessments.