USGS Washington Water Science Center
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WA286 - Stillaguamish River Basin Instream Flow and Water Quality - Completed FY1986
Problem - The State Department of Ecology (DOE) is determining required minimum flows for major streams in the State, including the Stillaguamish River. The Stillaguamish Tribe has a legal right to harvest fish in the river and to manage and protect this resource. However, water use in the basin has reduced flow so that at times sufficient water is not always available for spawning and rearing. The Tribe and DOE are attempting to reach a common agreement on minimum flow requirements; the Tribe has solicited technical assistance from the U.S. Geological Survey (USGS) for part of this effort.
Objectives - A technique has been developed by the Instream Flow Service Group (IFG) of the Fish and Wildlife Service (FWS) to monitor and document physical habitat conditions. The Stillaguamish Tribe has requested that the USGS gather the required data for the IFG analysis and apply the IFG model to the Stillaguamish River. In addition, we will collect and analyze baseline water-quality stream data in order to characterize the surface-water resources chemically.
Approach - Main-stream reaches and tributaries of the Stillaguamish River basin critical to various anadromous fish life stages will be selected and inventoried. The required data will be collected during low, medium, and high flows, and will consist of cross-section profiles both above and below water line, water depth, water velocity, substrate, cover, and general water quality. The computer simulation and analysis results will be compared to those of Swift (1979) in order to assess the relative suitabilities of both methods to adequately demonstrate or predict the effects of various flow regimes.