Keeping Fish Moving During Hot Times
Idaho Water temperatures at Lower Granite Dam exceeded allowable limits twice this past summer, temporarily stopping the adult runs of both sockeye and fall chinook salmon through the Snake River dam's fish ladder.
Managers "pulled out all the stops," according to Steve Hall, US Army Corps of Engineers, Walla Walla District, using every tool available, but at one time they still counted fewer adult fish traveling up the fish ladder than those returning to the river below the dam.
That was all due to temperatures exceeding the 68 degree limit (set by the federal Biological Opinion for salmon and steelhead) at the upstream end of the south fish ladder, with temperatures in two cases reaching as high as 74 degrees.
At its annual review of lessons learned, held last week in Portland, the Technical Management Team went through its list of tools -- cool augmenting water from Dworshak Dam and pumping cooler water (until it wasn't cool enough) from the depths of the Lower Granite Dam pool and into the fish ladder, as well as some spill and hydro operations -- but TMT still felt it came up short at least twice.
Two ideas that may be used in the future when temperatures in the lower Snake River again rise above levels detrimental to passing adults are longer hoses that pump cooler water that would extend from reservoir's lowest regions and drafting Dworshak below its minimum elevation level of 1,520 feet.
Neither was thought as good, or as possible, a solution as simply keeping the reservoir cool enough through the summer so that fish passing the dam would not be hindered or stopped by higher than normal temperatures in the bypass system.
Lower Granite is the last of eight hydro projects spawning salmon and steelhead must pass on their way to streams in Idaho, northeast Oregon and southeast Washington. Twice this year water temperatures between the fish ladder and the tailrace impeded adult passage.
The first incident was in late July when rising water and air temperatures in the Snake River basin resulted in water temperatures as high as 74 degrees in the upper fish ladder. High winds that mixed cool and warm waters in the reservoir exacerbated the temperature problem, leaving water at normally cool depths warmer than normal. That caused sockeye salmon migrating upstream to enter the fish ladder near the dam's tailrace, where water temperature was around 68 degrees, only to turn around at the top of the fish ladder before reaching the reservoir where the temperature was 74 degrees.
Snake River sockeye salmon were listed as endangered in 1991. The sockeye swim an additional 400 miles beyond Lower Granite Dam to spawning grounds in the upper Snake and Salmon rivers. Most of the returning fish will ultimately be trapped either at Sawtooth Hatchery near Stanley, Idaho, or in nearby Redfish Lake Creek.
The second incident was in early September when high water temperatures impacted migrating adult fall chinook.
The main tools available to fish managers - cool augmentation flows into the Lower Granite reservoir from Dworshak Dam on the North Fork of the Clearwater, which feeds into the Clearwater and then the lower Snake, pumping cooler water from the reservoir's depths through the fish ladder, and turbine operations - all failed.
In early August, a variety of operational changes were implemented. Emergency pumps, which were installed in 1992 to feed water into fish ladders during an experimental drawdown of Lower Granite's reservoir to test effects on juvenile salmon migration, were turned on.
Hall and some other river managers thought the pump hoses could be extended further into the reservoir's depths to draw out cooler water for a longer period of time.
In addition, turbine operations were switched back and forth in the hope that cooler water could be channeled toward the fish ladders to keep the entry at 68 degrees or less.
Hall creatively and painstakingly graphed the summer's week to week actions and resulting water temperatures at Lower Granite from July 1 to Sept. 23, providing the information at TMT's Lessons Learned workshop last week. These graphs, or "dashboards," are available at the TMT website.
Each graph includes flow and elevation at Dworshak Dam, flow out of the upper Snake River and flow, along with fish ladder and forebay temperatures at Lower Granite Dam. On July 22, flow from the cooler waters of Dworshak was at maximum, 12,100 cubic feet per second and elevation at the dam was about 1,586 feet, yet the upper fish ladder temperature, due to weather extremes, had reached 74 F.
While it impacted sockeye salmon adults, most had already passed the dam, according to information provided by Russ Kiefer, Idaho Fish & Wildlife. Yet, about 25 percent of sockeye counted at Lower Goose Dam downstream from Lower Granite Dam were unaccounted for, said Charles Morrill of the Washington Department of Fish & Wildlife.
In early September, temperatures in the upper fish ladder rose again to over 72 F, impacting adult chinook. By Sept. 16 Dworshak water was nearly depleted as it approached 1,520 feet and flows declined to 3 kcfs, its limit set by the Nez Pearce agreement. By Sept. 20, water in the fish ladder cooled to under 70 F. Most adult steelhead passed mid-September to mid-October.
Columbia System Gets Hotter and Deadly for Salmon and Steelhead by Rocky Barker, Idaho Statesman, 7/30/13
Climate Change Impacts Suggest Snake River Fish Passage Facilities Need 'Thermal/Hydraulic' Features by Staff, Columbia Basin Bulletin, 1/10/14
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