USGS Washington Water Science Center
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To implement and comply with the State of Washington Shoreline Management Act of 1971, the Washington State Department of Ecology (Ecology) needs estimates of the upstream boundary points for Washington streams. These boundary points are locations on the stream where the mean annual flow is 20 cubic feet per second (cfs), as defined by the Shoreline Management Act.
The USGS uses computerized geographic information systems (GIS), regression equations for precipitation, and other techniques to determine the 20-cfs points.
The USGS located these 20-cfs points in three phases. In Phase I, points were determined for streams in northwestern Washington. Phase II focuses on southwestern Washington. The focus of Phase III is on southeastern Washington.