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USGS Water Products
Understanding streamflow dynamics, watershed systems, and their relation to terrain characteristics is essential for describing and planning water supply, water use, and related land use activities. With data from over 1.5 million sites—and monitoring stations established for over 100 years—the U.S. Geological Survey (USGS) and the National Water Information System (NWIS) are the nation's repository of such water resources information. These data are used by government and non-governmental organizations to estimate future conditions and to assess risks such as flooding and drought. Planners and engineers use the data for designing systems for water supply, flood control, environmental protection, and recreation.
Watershed boundaries define the extent of surface water drainage to a given point, usually a stream confluence, taking into account topographic features and elevation gradients. The USGS Hydrologic Unit Code (HUC) system establishes a framework of drainage boundaries that create a hierarchical system of drainages (i.e., smaller watersheds nested within larger ones). Watershed boundaries are often formed along ridge lines, as surface water flows downslope and converges into water bodies such as streams and rivers.
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