This represents groundwater sub basins.
Data was taken from the Watershed Boundary Dataset as provided by the USGS. The Watershed Boundary Dataset (WBD) - is a nationally consistent watershed dataset that is subdivided into 6 levels (12-digit hucs) and is available from the USGS and USDA-NRCS-National Cartographic and Geospatial Center's (NCGC). The WBD contains the most current 8-digit, 10-digit and 12-digit hucs and are available below. A pdf file which lists the 2-digit, 4-digit, 6-digit and 8-digit hucs for the WBD and their naming convention is available at wbd_huc8.pdf.(this pdf file is no longer accurate).
