USGS Washington Water Science Center
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The City of Tacoma relies on surface water stored in the Howard A. Hanson Reservoir, in the Green River Basin in King County, to meet municipal needs and demands. Reservoir managers must also consider how allocation and use of the resource are affected by ongoing activities in the basin associated with fisheries enhancement and by rules implemented under the Endangered Species Act for salmonid fish proposed for listing.
To help managers continue to improve reservoir management strategies, the USGS is developing four different linear equations to estimate or forecast at long-lead times the monthly mean reservoir inflows for the months of April through July. At the latest, the estimates need to be made by mid-January. Developing the equations involves exploring the relations between monthly inflows and climatic information, precipitation, and temperature, identifying important variables to be used in the regression equations, and developing a list of these variables for each of the inflow months.