This data was prepared by the U.S. Environmental Protection Agency (EPA) in 1982 and include all hydrography shown on USGS maps having a scale of 1:250,000 with extensive additions, corrections and improvements in detail made by NOAA from aerial photography and satellite imagery. In the 1980's, RF1 was used by EPA for performing water quality modeling on whole river basins for all of the hydrologic regions in the conterminous United States. In this role, it was used to provide national assessments and overviews of water quality and to provide the foundation for a nationwide stratified sampling frame for performing statistical summaries of modeled and measured water quality on all the surface waters of the 48 States.
