This data set consists of geo-referenced digital map data and attribute data. The map data include complete coverage of the entire state including those subwatersheds crossing the borders of adjoining states. The digitized hydrologic units provide area extent of drainage patterns at the appropriate level of detail (basin, subbasin, watershed and subwatershed). Each polygon is linked to a set of attributes, including the hydrologic unit code and information on acreage, type, non-contributing area and trans-basin flow.
The data are distributed as a single arc export file (wshed), or as both a polygon (wshedp) and arc (wsheda) shapefile.
This data set is to be used as a primary reference source. This is public information and may be interpreted by organizations, agencies, units of government, or others based on needs; however, they are responsible for the appropriate application. Federal, state, or local regulatory bodies are not to reassign to the Natural Resources Conservation Service any authority for the decisions they make.
Photographic or digital enlargement of these maps to scales greater than that at which they were originally delineated can cause misrepresentation of the data. If enlarged, the maps will not include the fine detail that would be appropriate for mapping at the small scale. Digital data files are periodically updated, and users are responsible for obtaining the latest version of the data.
The typical size of a level 6 watershed is 10,000 to 40,000 acres. Not all watersheds exceeding 10,000 acres are delineated. Only those watersheds that show some unique cultural, physical, or logical significance are included in the data.
The order of precedence for establishing the pour point of a subwatershed is: (1) at the outlet of a lake or pond; (2) at a confluence; (3) at some topographic feature, such as a natural gap in topography; (4) at a dam; (5) at a stream gauging station.
A map unit symbol uniquely identifies each closed polygon. Each symbol is linked to a hydrologic unit code.