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Watersheds are defined by a combination of the hydrology and topography of the landscape. Watersheds are ubiquitous: no matter where you live, you live in a watershed. The U.S. Geological Survey has provided a standardized definition of watersheds that subdivide the country into 2,262 hydrologic units or watersheds. These watersheds provide a common basis of discussion for the public, planners, scientists and decisionmakers to deal with water issues. The links below are intended to provide a roadmap to these watersheds and the basic environmental data available describing the changing conditions within the watershed. Although social and economic data are not collected with respect to these natural boundaries, current geographic information systems and advances in information technology, allow reformatting these data sets into the common framework of watersheds.