PowerPoint Presentation
Flip-Flop Origins
- Major and Mighell (1969) estimated 30-50% mortality of spring chinook eggs from dewatering in upper Yakima River
- 1980 Quackenbush Decision mandated that the Yakima Project be operated to reduce impacts on fish. Minimum of 2 inches of water flowing over redd tailspills
- USBR established SOAC
- Flip-Flop was designed to protect fish and satisfy irrigation deliveries
The Flip-Flop Strategy
- Prevent de-watering of spring Chinook redds below upper Yakima dams
- Underlying assumption: spring Chinook production was limited by egg survival
- Decrease outflow during spring Chinook spawning
- Switch to water from Rimrock Reservoir to supply downstream water needs
Distribution
of spring Chinook spawning redds in the Yakima Basin,
1957–1961
Yakima and Naches Flows (2006)
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Naches River NR Naches Regulated, Unregulated Discharge Summary Hydrographs
Objectives of this Study
- Review in-basin and out-of-basin research related to the potential effects of Flip-Flop
- Analyze currently available data to quantify the effects of Flip-flop on spring Chinook
- Identify any needs for studies to fill critical data gaps
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What Information is Available?
- No estimate of the %redds dewatered as flow drops
- Adult escapement and spawning surveys
- Smolt abundance at Prosser
- Juvenile growth rates in the upper Yakima
- Juvenile habitat use in upper Yakima
- PIT tag detections to estimate smolt migration survival
Potential Tradeoffs
- Spring Chinook eggs gain some level of protection
- Is abundance of fry limiting spring chinook production?
- Is rearing capacity limiting production
- Is migration survival limiting production?
- Is salmonid production in the Naches Basin altered by Flip Flop?
Recruitment of Age-0+ Spring Chinook Rearing in the Upper Yakima River
Age-0+ Spring Chinook Size (Sept-Oct) Versus the Number of Redds the Year Prior
Potential Tradeoffs
- If juvenile rearing is the bottleneck,…
- Can we retrain Flip Flop, but also increase rearing capacity?
- OR…
- Can we gain more juvenile habitat by reducing summer flows, such that rearing gains exceed egg losses?
Rearing Habitat vs Flow
- Pearsons et al. 2006
- Compared habitable rearing area, based on depth velocities, in three reaches before and after Flip Flop
- Habitable area decreased in two reaches and increased in the third when flows dropped after flip flop
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Critical Data Gaps
- Determine the relationship of egg-to-fry survival to flows after spawning. How does the timing and magnitude of flow reduction affect egg survival?
- Observation or tracking of juvenile behavior to change in flow at time of Flip Flop. Do they shift habitats? What proportion migrate?
- Determine the relationship of parr habitat capacity to flow
- Estimate freshwater survival for each subbasin with substantial spring Chinook production
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