Friday, July 1, 2016
As a larger than predicted run of sockeye salmon head up the Columbia and Snake rivers ˆ some 400,000 fish -- the U.S. Army Corps of Engineers took steps this week to cool water in the lower Snake River.
At least 1,900 Snake River sockeye, listed under the Endangered Species Act, are predicted to move into the Snake River during this year‚s return.
Beginning Monday, the Corps increased the outflow at Dworshak Dam on the North Fork of the Clearwater River -- the additional water from the dam cools flows further downstream.
The Technical Management Team, an interagency panel that guides hydro operations throughout the basin, and the Corps are trying to keep water in the tailwater at Lower Granite Dam at a targeted 67 degrees Fahrenheit and no higher than 68 degrees.
In addition, TMT at its meeting Wednesday directed the Corps to close the surface spillway weir and modify spill at the dam, which has been an aid to juvenile fish passage. The largest chunk of juvenile yearling chinook salmon migrating out of the Snake River has already passed the dam as have nearly all of the juvenile sockeye salmon. TMT fisheries managers are uncertain what the impact will be for migrating subyearling chinook.
However, with the surface temperature of the water in the dam‚s reservoir already hitting 77 degrees F (25 degrees Centigrade) on an hourly basis, TMT fisheries managers worried that spilling the warm water would begin to create a thermal block below the dam, which is what happened in 2015 as the few sockeye that made it to the dam were stymied by the warm water and had to be trapped and hauled to Eagle Hatchery in Idaho.
The RSW draws water from the surface waters and passes that water downstream of the project. The goal for the adult sockeye migration is to maintain the water below the dam as cool as possible, according to Paul Wagner of NOAA Fisheries. The fisheries managers agreed to close the surface weir and transfer that volume of spill to the deeper spill bays that draw water from a depth of 50 feet which is much cooler at 67 degrees (19.5C) than the surface weir location.
While it is not certain where the subyearlings pass the project during these warm periods, the volume of spill passing the project will not change, Wagner said.
It‚s been warm in the lower Snake River basin and is predicted to be even warmer, according to Steve Hall, the Corps‚ Walla Walla District reservoir manager, at TMT‚s meeting.
After a weekend of relatively low flowsˆ set at about 2,400 cubic feet per second ˆ from the now full Dworshak Reservoir, the Corps increased flows Monday to help cool Lower Granite water. The release of water does not have an immediate affect at Lower Granite and so releases from Dworshak must be timed in order to keep water temperatures within the acceptable range at the Snake River dam.
"It takes about three days for cold-water releases from Dworshak to reach the downstream side of Lower Granite Dam, where the target temperature gauges are located. So, we have to plan well ahead and make adjustments at Dworshak that will be effective at the time we'll need them further down the river," Hall said. "We are required to maintain water temperatures at Lower Granite below 68 degrees, if possible, using available reservoir-system management methods."
Hall said that over the weekend the Corps was conserving water and ensuring the reservoir was as full as possible. Prior to Monday‚s release, the reservoir was at an elevation of about 1,600 feet, which is considered full.
The Corps gradually ramped up flow Monday and about 2 pm it reached what it calls full powerhouse, generally a discharge of 9.8 kcfs, but Hall said full powerhouse currently is closer to 9.4 kcfs. Water elevation in the Clearwater River downstream of the dam also increased by about one-half to two-thirds feet at the North Fork confluence.
One of the factors that is warming the lower Snake River is discharges at Idaho Power‚s Hells Canyon Dam as the power company generates electricity for air conditioning in the region.
Based on modeling, the higher outflow at Dworshak Dam will lower the reservoir level by about 10 inches per day. Still, the reservoir will be within 5 to 7 feet of full over this holiday weekend.
According to Corps information, NOAA Fisheries Columbia River System Biological Opinion requires the Corps to meet several objectives to enhance ESA-listed fish survival, including maintaining minimum water flows for resident fish and salmon, and releasing Dworshak Reservoir water to maintain lower Snake River water temperatures and help speed juvenile fish downriver to the ocean.
"With such hot weather forecasted to continue, water temperature at Lower Granite could soon exceed 68 degrees if not regulated, creating conditions in the reservoir system that are unhealthy for ESA-listed fish," Hall said. "Dworshak's 43-degree outflows make a big difference in water temperature there and further down the Snake River."
Snake River sockeye salmon are listed as endangered under the federal Endangered Species Act. There is growing evidence that summer sockeye are the most vulnerable to harm from warm water, compared with other salmon runs.
The sockeye run this year was predicted by the U.S. v Oregon Technical Advisory Committee in its pre-season forecast to be 101,600 fish, far fewer fish than the 512,500 sockeye that returned in 2015 and below the 10-year average of 290,200. However, 284,345 sockeye had already passed Bonneville Dam as of Thursday this week. The 10-year average on this date is 193,277 (see www.fpc.org for fish passage information).
TAC updated its predicted run size of sockeye Monday, increasing its estimate to 400,000 sockeye.
As of yesterday, 231,012 of the sockeye have reached The Dalles Dam, 226,807 the John Day Dam, 190,670 McNary Dam, and some fish are already in the lower Snake River with 275 over Ice Harbor Dam, 240 over Lower Monumental Dam, 110 at Little Goose Dam and 57 at Lower Granite Dam. Last year at this time, 67 sockeye had passed Lower Granite. The 10-year average at Lower Granite is 37 as of July 30.
Last year at this time, 357,363 sockeye had passed Bonneville Dam, 290,982 at The Dalles, 252,225 at John Day, 183,687 at McNary, 372 at Ice Harbor, 313 at Lower Monumental, 150 at Little Goose, and 75 sockeye at Lower Granite.
In 2015, low flow conditions, coupled with extremely high air temperatures and warm water in the major tributaries in the lower Snake and Columbia rivers from mid-June to mid-July, resulted in the highest mainstem temperatures recorded in the Columbia River.
At 68 degrees F sockeye salmon begin to die and most of the fish passed Bonneville Dam in 2015 after the water temperature had hit 73 degrees.
For background, see CBB, April 15, 2016, „NW Power/Conservation Council Hears ŒLessons Learned‚ Report On High Mortality For 2015 Sockeye Run,‰ http://www.cbbulletin.com/436491.aspx
Some 99 percent of Snake River sockeye that were counted crossing Bonneville Dam died before they reached the upper Salmon River‚s Sawtooth Valley where the salmon spawn. Just 56 adult sockeye salmon made it on their own to the Sawtooth Valley and another 51 were transported from a trap at Lower Granite Dam to the Eagle Hatchery in Idaho.
And only 3 percent to 4.5 percent of the fish heading up the Columbia River and into the Okanagan River ever made it to the spawning grounds. Some 10 percent to 15 percent made it to the Wenatchee River to spawn, the passage report said.
Since last year, the Corps has installed a permanent adult fish ladder water cooling system that pulls cold water from deep in the Lower Granite forebay into the fish ladder.
A similar device at Little Goose Dam is set to be in operation this week. It pumps water from 60 feet in the Little Goose reservoir, where there is 63 degree water, into the dam‚s fish ladder. Surface water highs at the dam are in the 70s, according to the Corps.
(See Corps information on the project at http://www.nww.usace.army.mil/Missions/Fish-Programs/Lower-Granite-Fish-Ladder-Temperature-Improvement/
and CBB, June 17, 2016, „Corps Moves Forward On Fish Passage Improvements At Lower Granite Dam, Includes Fish Ladder Cooling,‰ http://www.cbbulletin.com/436933.aspx)
For more information, see:
--CBB, June 24, 2016, „Columbia Basin Salmon/Hydro Managers Gear Up For Another Hot Summer: Will Sockeye Get Slammed Again?‰ http://www.cbbulletin.com/436997.aspx
--CBB, April 1, 2016, „Corps Report On 2015 Columbia/Snake Warm Water, Fish Die-Off Will Discuss Actions To Avoid Repeat,‰ http://www.cbbulletin.com/436358.aspx
-- CBB, December 4, 2015, „Post-Mortem 2015 Snake River Sockeye Run; 90 Percent Of Fish Dead Before Reaching Ice Harbor Dam,‰ http://www.cbbulletin.com/435642.aspx
-- CBB, November 6, 2015, „Report Analyzes Impacts, Causes Of This Year‚s Warm Fish-Killing Water In Columbia/Snake,‰ http://www.cbbulletin.com/435505.aspx