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Hot Weather Forces Dworshak Flow Increase to Cool Lower Snake by Staff Columbia Basin Bulletin, June 26, 2015

Snake River Sockeye Passing Bonneville

Hot weather, warm water and lower than average flows in the Snake River dominated the regional Technical Management Team meeting this week, but Russ Keifer of the Idaho Department of Fish and Game also had good news about Snake River sockeye adults passing Bonneville Dam.

"As of last night, 109 PIT-tagged Snake River sockeye salmon had passed Bonneville Dam," Keifer said. "That translates to 532 sockeye coming up the river, so it looks like another good return for the Snake River sockeye."

However, warm and low water could slow the sockeye adult migration and TMT is working to keep the river as cool as possible.

A long hot spell with temperatures in the upper 90s and lower 100s is heating tailwater at Lower Granite Dam on the lower Snake River dangerously close to 68 degrees Fahrenheit, the limit allowed by a NOAA Fisheries biological opinion.

As a result, the U.S. Army Corps of Engineers increased the flow of Dworshak's cold water Wednesday this week at midnight. Dworshak flows rose to 8,500 cubic feet per second, an increase from flows set last Tuesday at 5.3 kcfs, which also was intended to cool tailwater at Lower Granite. Previously flows had been 2.9 kcfs.

Water released from Dworshak Dam on the North Fork of the Clearwater River, a tributary of the Snake River, is about 42 degrees this week and provides a boost of cool water for projects lower in the river.

"We're having record highs continuously day after day," Kevin Schneidmiller of the Corps' Walla Walla office told TMT this week. "We're surprised."

He said the Corps will continue to model daytime temperature and Lower Granite tailwater temperature through the weekend to determine if it needs to go to full powerhouse flows, which is about 10 kcfs.

Given this current operation, by the end of July, flows would have to drop to 8.5 kcfs or less and would be 4 kcfs to 7 kcfs for most of August in order to preserve Dworshak water, said Steve Hall of the Corps' Walla Walla office. Another scenario would be to release closer to gas cap, about 13.5 kcfs, through July and go to 4 kcfs in August.

"We're doing our best to stay close to the 68 degrees and not exceed our target through the weekend," Hall said. "It takes three days for water to reach Lower Granite from Dworshak, so we have to look out ahead."

Also at TMT this week salmon managers questioned an agreement that allowed the Corps to move from spilling 30 percent of the river at Little Goose Dam to a flat spill rate when flows dropped below 32 kcfs.

"I think we're dropping spill levels lower than we agreed to," said Russ Keifer of the Idaho Department of Fish and Game. "With this new flat spill, we've been dropping down below 30 percent spill on some days."

Doug Baus of the Corps disagreed, saying it was a TMT agreement and that, since the operation began last week, spill on a daily average has been above 30 percent, although there have been some drops.

"We made this operation to finish the spill season as best we can," Baus said, pointing to the lower than usual water this year. "We're doing in June what we would normally do in August."

Keifer said what he is seeing is a lot of variability, but thought the spill regime set at TMT in 2008 for Little Goose was a flat 11 kcfs spill when flows fall below 32 kcfs, 9 kcfs spill when flows fall below 28 kcfs and 7 kcfs spill when they fall below 26 kcfs, but he was having trouble tracking down the documentation.

A portion of this operation had already been incorporated into the 2015 fish operations plan (FOP). Baus pointed out that when flows drop below 28 kcfs, the spill percentage actually goes up (9 kcfs/28 kcfs = 32 percent).

After a meeting of salmon managers Wednesday afternoon to discuss the issue, TMT met again Thursday morning and salmon managers proposed a system operations request laying out the precise operation they wanted.

Offering its history, Keifer said the operation was developed over time beginning in late August 2008 when low flows that fell to under 32 kcfs at Little Goose, along with power house limitations, made it difficult to hold a percentage spill, so TMT agreed to go to a flat spill of 11 kcfs.

In August 2009, flows fell below 28 kcfs, so TMT set a flat spill at 9 kcfs. By the end of August, flows were even less, 24 kcfs, so TMT set a flat spill of 7 kcfs.

This week's SOR is similar to the historical record, setting flat spill at 11 kcfs when flows are equal to or less than 32 kcfs and more than 28 kcfs; 9 kcfs of spill when flows are equal to or less than 28 kcfs and more than 24 kcfs; 7 kcfs when flows are less than 24 kcfs. When Little Goose can't spill 7 kcfs and maintain the power house minimum, then spill would be the excess water of the power house minimum.

The action agencies and fish managers agreed to use the previous day's daily average flow to determine the current day's spill operation, automatically going to the day's operations in the early morning hours. If flows rise above 32 kcfs, spill will revert to 30 percent of the river, according to the Corps.

Farther upstream on the Snake River, flows over Shoshone Falls will drop beginning tonight (June 26) as the volume of water passing Milner Dam falls to about half of its current level.

Idaho Power will maintain a minimum flow of 300 cfs over Shoshone Falls, with the remaining water being diverted through its power plant for electricity generation.

Snake River flows below Milner Dam, located between Twin Falls and Burley, will drop from the current level of 1,500 cfs to about 750 cfs by 6 p.m. today.

Idaho Power-owned water in American Falls Reservoir has been released by the U.S. Bureau of Reclamation, which operates the reservoir, over the past several weeks, keeping flows at their current level. That release is now complete. Idaho Power has leased additional water from the Shoshone-Bannock Tribe, which will begin flowing through the company's hydroelectric system as the company anticipates high electrical demand during the coming heat wave.

That water will last until late July, when flows are expected to drop to zero below Milner.

The changing water level will impact river users all along the Snake River. Irrigators with pumps need to be aware that the river will begin dropping Friday. Anglers and other users should be aware of the falling river levels as well. Return flows will add some volume downstream, but river users should expect very low flows downstream to Brownlee Reservoir.