U.S. Geological Survey. National Hydrography Dataset high-resolution flowline data. The National MapArchived 2016-06-30 at the Wayback Machine, accessed March 21, 2011
web.archive.org
U.S. Geological Survey. National Hydrography Dataset high-resolution flowline data. The National MapArchived 2016-06-30 at the Wayback Machine, accessed March 21, 2011