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News Release

U.S. Department of the Interior
U.S. Geological Survey

Release: November 29, 2000
John Vaccaro
253-428-3600, ext. 2620

New Forecasting Method Helps Guide Reservoir Releases

A new experimental method to forecast streamflows coming into reservoirs will help guide decisions to release or store water, according to a report published today by the Department of the Interior, U.S. Geological Survey (USGS). The method was developed in cooperation with Tacoma Public Utilities, Seattle Public Utilities, and the U.S. Army Corps of Engineers.

Managing a reservoir requires carefully timing the release of water to meet the often conflicting demands of spawning salmon and seasonal water needs. The new method gives reservoir managers a tool to predict from 2-14 months ahead of time the amount of streamflow coming in, taking away a lot of uncertainty about how much water to release or store.

The method was used to forecast streamflow into Howard A. Hanson Reservoir on the Green River. It can also be applied to nearby Chester Morse Lake on the Cedar River. Both reservoirs are important water sources for Tacoma and Seattle.

Forecasting equations in the new method take into account climate-forcing variables like atmospheric circulation, sea surface temperatures, rainfall, and sunspot numbers. These variables are related to how much water will find its way into Washington streams.

"The approach is based on the well-documented, strong link between climate- forcing mechanisms in our hemisphere and streamflow in the Pacific Northwest," said John Vaccaro, USGS hydrologist and author of the report.

The report, "Development, Testing, and Assessment of Regression Equations for Experimental Forecasts of Fall-Transition-Season Inflows to the Howard A. Hanson Reservoir, Green River, Washington," is published as a USGS Water-Resources Investigations Report 00-4153. Copies are available for reading at the U.S. Geological Survey, 1201 Pacific Avenue, Suite 600, Tacoma, Washington 98402. Copies can be purchased from the U.S. Geological Survey, Information Services, Box 25286, Federal Center, Denver, CO 80225-0286, telephone (303) 202-4200.

As the Nation's largest water, earth and biological science, and civilian mapping agency, the USGS works in cooperation with more than 2,000 organizations across the country to provide reliable, impartial scientific information to resource managers, planners, and other customers. This information is gathered in every state by USGS scientists to minimize the loss of life and property from natural disasters, contribute to the sound conservation and the economic and physical development of the nation's natural resources, and enhance the quality of life by monitoring water, biological, energy, and mineral resources.

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