U.S. Geological Survey. National Hydrography Dataset high-resolution flowline data. The National MapArchived 2016-06-30 at the Wayback Machine, accessed April 27, 2011
U.S. Geological Survey. National Hydrography Dataset high-resolution flowline data. The National MapArchived 2016-06-30 at the Wayback Machine, accessed April 27, 2011