This dataset contains subwatersheds (HUC 12-digit)
within basins intersecting the Colorado Plateau, Arizona/New Mexico
Plateau, and Sonoran Desert eco-regions in the southwestern United
States. It is an extract of the National Watershed Boundary Dataset
(WBD), obtained January 2011. For more information on the WBD, see
http://www.ncgc.nrcs.usda.gov/products/datasets/watershed/index.html .