EPA Reach File References

The U.S. Environmental Protection Agency's (USEPA) Reach Files are a series of national hydrologic databases that uniquely identify and interconnect the stream segments or "reaches" that comprise the Country's surface water drainage system. The three versions of the Reach File that currently exist, known as RF1, RF2, and RF3-Alpha respectively, were created from increasingly detailed sets of digital hydrography data produced by the U.S. Geological Survey. RF1, at a scale of 1:500,000, is still utilized while RF2 and RF3, at a scale of 1:100,000, have been superseded by the National Hydrography Dataset (NHD). The USEPA enhanced these hydrography datasets by assigning a unique reach code to each stream segment, determining the upstream/downstream relationships of each reach, and, when possible, identifying the stream name for each reach. A variety of other reach-related attributes that support mapping and spatial analysis applications, such as the stream level attribute, are also available. Click on the graphic below to explore the various Reach File references.

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