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Water: Georeferencing

A Brief History of Reach Files

The Reach File was first conceived in the 1970s with a proof-of-concept database, known as Reach File Version 1.0 Alpha (RF1-Alpha), completed in 1975. The first full implementation, referred to as Reach File Version 1.0 (RF1), was completed in 1982. The source for RF1 was the U.S. Geological Survey's (USGS) 1:250,000-scale hydrography that had been photo-reduced to a scale of 1:500,000 by the National Oceanic and Atmospheric Administration (NOAA). RF1 consists of approximately 68,000 reaches comprising 650,000 miles of stream. RF1 is still in use for national-level problem analysis.

While RF1 still supports broad-based national applications, the need to provide a complementary and more detailed hydrologic network motivated the development of Reach File Version 2.0 (RF2) in the late 1980's. RF2 was created by using the Feature File of the USGS Geographic Names Information System Version 1 (GNIS I) to add one new level of reaches to RF1. RF2 contains 170,000 reaches. Shortly thereafter, widespread interest in providing a more comprehensive, nationally consistent hydrologic database prompted the effort to produce Reach File Version 3.0 (RF3).

In 1997, RF3 was "frozen" so that efforts could be focused on building the next generation, which is a combined map and routing system called the National Hydrography Dataset (NHD). NHD is the next generation reach file that combines in one database the official USGS National Mapping Division digital maps and the EPA Reach File. The RF3 was overlayed onto the most current version of the USGS 1:100,000 scale DLG using a combination of automated and manual processes with detailed quality control of the network. The NHD will be maintained by USGS, with initial retrievals from this database by subbasin (formerly cataloging unit). The NHD includes Washington, Oregon, and Idaho, which were not available in RF3.

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Figure 3. RF3(1992-1997)
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Figure 4. NHD (1999)
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