U.S. Geological Survey. National Hydrography Dataset high-resolution flowline data. The National MapArchived 2017-08-23 at the Wayback Machine, accessed April 1, 2011
web.archive.org
U.S. Geological Survey. National Hydrography Dataset high-resolution flowline data. The National MapArchived 2017-08-23 at the Wayback Machine, accessed April 1, 2011