This Year’s Operations At Dworshak Dam Keep Snake River At Lower Granite Dam Cool Enough For Salmon Through August

A U.S. Army Corps of Engineers’ operation that began July 1 to maintain tailwater temperatures at Lower Granite Dam under 68 degrees Fahrenheit by releasing cool water from Dworshak Dam into the lower Snake River system is coming to an end this weekend.

68 degrees is the maximum allowed by NOAA Fisheries’ biological opinion on impacts of the federal hydroelectric system on salmon and steelhead. Temperatures higher than 68 degrees can be lethal to both adult and juvenile salmonids migrating in the river, including endangered Snake River sockeye salmon arriving in late July and early August.

However, beginning Sept. 1, that operation that had successfully maintained cool tailwater temperatures downstream at Lower Granite will be replaced by flow augmentation of 200,000-acre feet through most of September. The 200 kaf is required by the Snake River Basin Adjudication, according to Jay Hesse of the Nez Perce Tribe. The water from the Dworshak Dam reservoir, located on the North Fork Clearwater River, will continue to cool Lower Granite’s tailwater and it will also cool lower Clearwater River water temperatures as adult Chinook salmon arrive in the river to spawn.

The Snake River Basin Adjudication is an agreement that gives the Tribe a claim each year on 200 kaf of water stored in the Dworshak reservoir. It will use that water allotment during September. The Agreement stems from an April 20, 2004 document titled “Mediators Term Sheet,” which was included in the Snake River Water Rights Act of 2004.

All of that water is available but only as long as the reservoir’s elevation on Aug. 31 each year is at least at 1,535 feet, which is the case this year. The elevation Aug. 28 was 1,539.45 feet, as was reported by Jessica Sollider of the Corps’ Walla Walla District office at this week’s interagency Technical Management Team meeting.

Hesse said the Dworshak Board of Directors that oversees the operational plan for the 200 kaf is recommending that the current water releases from Dworshak begin to be gradually ramped down Sept. 1 from the current 9,200 cubic feet per second with the hope that the Tribe’s 200 kaf of water will last at least through Sept. 27 when the reservoir reaches an elevation of 1,520 feet, the minimum for the end of September. A final plan by the Board, he said, was released Wednesday, Aug. 28 and posted to the TMT website at https://pweb.crohms.org/tmt/agendas/2024/0828_Base_DWR_Operational_Plan_Aug_2024_Final_0829.pdf

“Releases of cool water from Dworshak Dam reduce summer temperatures and drafting of the reservoir improves flows in the lower Snake River, improving conditions for migrating smolts, juveniles rearing in the reservoirs, and adult migrants,” the operational plan says.

A memorandum of agreement for the 200 kaf was signed in 2005 by the Tribe, the Corps, the Bonneville Power Administration, NOAA Fisheries and the state of Idaho.

The Board consists of each of the parties to the original MOA. According to the plan, it describes “the intended operation under the assumption that pending environmental conditions and actual operations will be consistent with an August 31 pool elevation of at least 1,535 feet.”

The reason the Corps was able this year to meet the minimum pool level in the Dworshak reservoir that sets the stage for the 200 kaf is due to lower-than-expected air temperatures and falling water temperatures in August, in addition to an alternative management operation recommended by TMT’s fisheries managers and implemented by the Corps the first eight days of August, according to an overview of the July through August operation for TMT by Willow Walker of the Corps’ Walla Walla District.

In her overview, Walker said that at a July 24 meeting, TMT members discussed three risk management alternative operations for Dworshak’s water supply and had decided on a “relaxed temperature criterion” that raised the maximum Lower Granite tailwater temperature from the BiOp maximum of 68 degrees F to 69.5 F from Aug. 1st to Aug. 9th.

“The alternative operation was intended to save as much water as possible in Dworshak reservoir during the specified time window that aligned with the anticipated lull in passage shifting between the Sockeye to the fall Chinook run in the Lower Snake River,” she said in her overview. “The water saved from the temperature relaxation would then be used in the latter part of August when more Chinook are present and broodstock operations occur.”

Before alternative operation was brought into play, the chances of maintaining the required 68 F temperature in Lower Granite’s tailwater was more limited. Walker said there was enough water to maintain 68 F in Lower Granite’s tailwater through the end of August only if average conditions occurred. That would require that the lower Snake River would have no heatwaves and that three days of spill could be used to mitigate increased tailwater temperatures during Lower Granite’s doble testing.

“Thanks to the selected adaptive operation as well as cooler ambient air temperatures at the end of July, an additional 2.5 days of spill are now available for operations outside of doble testing,” Walker concluded in her overview. “These extra days can be utilized in the face of another heatwave or other event.”

Walker’s overview can be found at https://pweb.crohms.org/tmt/agendas/2024/0814_DWR-Summer-Water-Supply-Outlook_Update.pdf.

A Doble test is maintenance on a transformer and checks the integrity of the transformer conductors, according to Tom Conning, public affairs specialist with the Corps’ Northwest Division.

“Turbine generators generate electrical power (in the form of voltage and current) and that power is transmitted to the grid through a transformer,” he said in an email. “The transformer steps up the generated voltage to match the voltage of the line or grid, where that power then flows to the load, where another transformer (local to the load) steps down the voltage to a useable value.

“When we do a Doble test, the units are unable to generate or send power to the grid. Generally, we cannot utilize the turbines, so projects have to spill water. We typically can run 1 unit at speed no load which means the generator is running at speed with no significant power output, greatly reducing the amount of water that is released through the powerhouse.”

TMT is an inter-agency group that consists of sovereign representatives from: the tribes of Nez Perce, Kootenai, Colville, Umatilla, Spokane, and Warm Springs; the states of Oregon, Washington, Idaho, and Montana; NOAA Fisheries; US Fish and Wildlife Service; and the federal Action Agencies – the Bureau of Reclamation, the Corps and the Bonneville Power Administration. TMT responsibilities generally function to address changing conditions, such as water supply, fish migration, water quality, new information, and maintenance issues as it pertains to dam operations in an effort to meet the expectations of applicable biological opinions.

TMT’s goal is to protect fish by recommending beneficial operations, including spill, temperature, and flows for ESA-listed salmon, steelhead, sturgeon, and bull trout species within the Columbia River Basin, according to a statement by the Corps. While the TMT encourages conversation, Action Agencies are responsible for management and operation of the Columbia River System. The TMT members can make a recommendation for fish and wildlife benefits to the Action Agencies for their consideration, but the Action Agencies cannot accommodate all requests.

Dam, stream and weather information used at this week’s TMT meeting can be found here: https://pweb.crohms.org/tmt/agendas/2024/0828_Agenda.html

For background, see:

— CBB, July 5, 2024, With Air, Water Temps In Lower Snake Heating Up, Corps Releasing Cool Dworshak Flows To Aid Salmon, Steelhead, https://columbiabasinbulletin.org/with-air-water-temps-in-lower-snake-heating-up-corps-releasing-cool-dworshak-flows-to-aid-salmon-steelhead/

— CBB, June 21, 2024, BASIN SUMMER WATER SUPPLY? RECORD LOW SNOWPACKS IN THE NORTH, ABOVE NORMAL SOUTHERN IDAHO, DALLES DAM RUNOFF 77 PERCENT OF AVERAGE, HTTPS://CBBULLETIN.COM/BASIN-SUMMER-WATER-SUPPLY-RECORD-LOW-SNOWPACKS-IN-THE-NORTH-ABOVE-NORMAL-SOUTHERN-IDAHO-DALLES-DAM-RUNOFF-77-PERCENT-OF-AVERAGE/

— CBB, March 7, 2024, FEBRUARY’S LOWER TEMPS, NORMAL PRECIP GIVES SLIGHT IMPROVEMENT TO COLUMBIA BASIN APRIL-AUGUST WATER SUPPLY FORECAST; 83 PERCENT OF AVERAGE, HTTPS://CBBULLETIN.COM/FEBRUARYS-LOWER-TEMPS-NORMAL-PRECIP-GIVES-SLIGHT-IMPROVEMENT-TO-COLUMBIA-BASIN-APRIL-AUGUST-WATER-SUPPLY-FORECAST-83-PERCENT-OF-AVERAGE/

— CBB, February 16, 2024, BASIN WATER SUPPLY DROPPING WITH MOST WATERSHEDS WELL BELOW NORMAL, SETTING UP LOW EXPECTATIONS FOR THE YEAR, HTTPS://CBBULLETIN.COM/BASIN-WATER-SUPPLY-DROPPING-WITH-MOST-WATERSHEDS-WELL-BELOW-NORMAL-SETTING-UP-LOW-EXPECTATIONS-FOR-THE-YEAR/

— CBB, January 18, 2024, SEEMS LIKE A LOT OF SNOWY, WET WEATHER, BUT COLUMBIA BASIN WATER SUPPLY LIKELY TO REMAIN BELOW NORMAL; 77 PERCENT AT DALLES DAM, HTTPS://CBBULLETIN.COM/SEEMS-LIKE-A-LOT-OF-SNOWY-WET-WEATHER-BUT-COLUMBIA-BASIN-WATER-SUPPLY-LIKELY-TO-REMAIN-BELOW-NORMAL-77-PERCENT-AT-DALLES-DAM/

— CBB, August 23, 2023, NEZ PERCE MOA ON DWORSHAK WATER HELPS KEEP CLEARWATER, LOWER SNAKE RIVER COOL IN SEPTEMBER FOR MIGRATING, OVER-WINTERING SALMON, STEELHEAD, HTTPS://CBBULLETIN.COM/NEZ-PERCE-MOA-ON-DWORSHAK-WATER-HELPS-KEEP-CLEARWATER-LOWER-SNAKE-RIVER-COOL-IN-SEPTEMBER-FOR-MIGRATING-OVER-WINTERING-SALMON-STEELHEAD/

— CBB, July 27, 2023, FISHERY MANAGERS PREPARE FOR ALLOWING DWORSHAK’S COOLING WATER FOR LOWER SNAKE TO LAST LONGER; SOCKEYE RUN ‘NOT A PRETTY PICTURE’ https://columbiabasinbulletin.org/fishery-managers-prepare-for-allowing-dworshaks-cooling-water-for-lower-snake-to-last-longer-sockeye-run-not-a-pretty-picture/

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This Year’s Operations At Dworshak Dam Keep Snake River At Lower Granite Dam Cool Enough For Salmon Through August

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