U.S. Geological Survey. National Hydrography Dataset high-resolution flowline data. The National MapArchived March 29, 2012, at the Wayback Machine, accessed April 1, 2011
U.S. Geological Survey. National Hydrography Dataset high-resolution flowline data. The National MapArchived March 29, 2012, at the Wayback Machine, accessed April 1, 2011