USGS Washington Water Science Center
|U.S. Department of the Interior
U.S. Geological Survey
Release: February 25, 2004
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[Note: The report can be viewed on the Web at http://pubs.water.usgs.gov/sir2004-5016/ .]
Streamflow in the Puyallup River dips below state-required levels, and analysis suggests a link to water releases from Lake Tapps, according to a report released by the USGS, in cooperation with the Puyallup Tribe of Indians.
The Washington Department of Ecology sets the minimum water levels or flows in rivers, called “instream flows,” needed to protect fish and other wildlife as well as to preserve rivers for human uses. In the Puyallup River, minimum instream flows, which vary with natural conditions throughout the year, are set for several locations.
Scientists from the USGS looked for trends in streamflow in the lower Puyallup River Basin to help the Puyallup Tribe manage their fish hatchery and water resources. To find any trends, they evaluated daily mean flow (average flow for the day), daily minimum flow, and unit-value flow (flow measured every 15 minutes) values. Scientists also compared those values with instream flows set for the river. Although they didn’t find any significant trends in daily average streamflows, the scientists did find a couple of notable results.
“Using 15-minute flows showed us a rise-and-fall pattern in streamflow that closely echoed the release of water from the dam at Lake Tapps,” said USGS hydrologist Steve Sumioka, author of the report. “If you look only at daily average flows, you may miss seeing streamflow dropping below the minimum instream flows that appeared when we used 15-minute flows.”
“By using streamflow measured every 15 minutes, you get much more information about meeting instream flows than you would using only an average flow for the day.”
Meeting instream flow requirements is highly important to successfully manage Tribal fisheries and water resources, according to Char Naylor, water-quality manager for the Tribe. The Tribe is both a co-manager of fisheries and a water-quality regulator in the lower Puyallup River Basin.
The analysis of streamflow conducted by Sumioka follows up on two previous USGS studies of the lower Puyallup River. See http://wa.water.usgs.gov/projects/puyallup/ for more information.
The report, “Trends in Streamflow and Comparisons With Instream Flows in the Lower Puyallup River Basin, Washington,” by Steve S. Sumioka, is published as U.S. Geological Survey Scientific Investigations Report 2004-5016. The report can be viewed on the Web at http://pubs.water.usgs.gov/sir2004-5016/ . Copies can be purchased from the U.S. Geological Survey, Information Services, Box 25286, Federal Center, Denver, CO 80225-0286, telephone 303-202-4200.
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