The National Map
Data on America's surface waters are available from the USGS in the National Hydrography Dataset (NHD). The NHD includes datasets covering all streams and lakes at scales of 1:24,000 and 1:100,000. In some areas, the NHD is being supplemented with data larger than 1:24,000-scale. The NHD provides a true network that supports the analysis of any type of movement (for example, navigation, sediment transport, and effluent dispersion) by surface waters. Further information and data download are available at http://nhd.usgs.gov/.
The Watershed Boundary Dataset (WBD) defines the areal extent of surface water drainage to a point, accounting for all land and surface areas. Watershed boundaries are determined solely upon science-based hydrologic principles, not favoring any administrative boundaries or special projects, nor a particular program or agency. The intent of defining Hydrologic Units (HUs) for the WBD is to establish a base-line drainage boundary framework. At a minimum, the WBD is being delineated and geo-referenced to the USGS 1:24,000 scale topographic base maps, except for Alaska at 1:63,360 scale, and 1:25,000 scale in the Caribbean, to meet National Map Accuracy Standards. More information is available at http://nhd.usgs.gov/wbd.html.