With salmon counts lagging at the Bonneville Dam, fish and hydro system managers have ventured into relatively new territory by holding back a share of the incoming for a four-hour period Thursday from a surging Columbia River in an attempt to entice movement of what was expected to be a bumper upriver run.
The U.S. Army Corps of Engineers, at the request of salmon managers, scaled back gushing flows through the spillway at Bonneville, and to some degree through the hydro turbines, to see if unusually high flows this year are daunting upriver spring chinook salmon.
Preliminary results being gathered Thursday afternoon did not seem to indicate a huge surge—though numbers were up -- had been triggered by the operational test, according to Doug Baus of the Corps’ Water Management Division. The Technical Management Team, made up of federal, state and tribal salmon and hydro management representatives, was set to meet today to evaluate the operation, and decide it if it might be tried again.
“It didn’t seem like there was an immediate response,” Baus said of preliminary dam passage information in hand late Thursday afternoon.
The Technical Advisory Committee, also made up of federal, state and tribal officials, met Monday to review the progress of the upriver spring chinook salmon run and concluded that it “is unlikely to meet the preseason forecast of 314,200 fish at the river mouth.”
That forecast, if fulfilled, would represent the fourth highest return since 1980, and 156 percent of the average return observed over the past decade. It was based to some degree on the fact that the second largest count of jacks on record was counted last year. Jacks are fish that return after only one year in the ocean. Most of their broodmates are expected to return this year and next as 4 and 5 year olds.
But, through Thursday only 29,992 adult salmon had been counted at Bonneville’s fish ladders, which is the second lowest count through that date in the past 10 years. The lowest count in the past 10 years through May 3 was 13,316 in 2006, when the final run-size estimate was 132,600 fish to the river mouth. The Washington Department of Fish and Wildlife guides the counting operations at Columbia and Snake river mainstem dams, which are operated by the Corps.
The 2011 upriver spring chinook return to the Columbia River mouth totaled 221,200 adults. Through May 3 last year a total of 68,752 springers had passed over Bonneville
Based on the 10-year average, 50 percent of the upriver run will have passed Bonneville by May 6 (range April 24-May 12), according to TAC.
Bonneville is 146 river miles upstream from the Pacific. The “upriver” spring chinook run includes fish bound for hatcheries and tributary spawning grounds above Bonneville in Idaho, Oregon and Washington.
Flows through Bonneville Dam have been over 400,000 cubic feet per second April 26-29, with 46 percent of the flow coming from spill.
Flows through Bonneville started and ended the day Thursday at or near 429 kcfs. During the holdback that ended about 9 a.m. flows were decreased to as little as 333 kcfs. Most of the cutback was achieved by reducing spill, though flows through turbines were eased. Spill during recent high flows has been well above standards required for fish passage by NOAA Fisheries’ Federal Columbia River Power System biological opinion.
The BiOp prescribes 100 kcfs in spill in springtime to provide downstream passage for juvenile spring chinook – wild Upper Columbia and Snake River fish – that are listed under the Endangered Species Act. Spill in April averaged nearly 125 kcfs and during the first three days of May averaged 176.8 kcfs.
Upriver spring chinook counts appeared to be on the rise with a peak of 4,873 adult fish counted April 24, but as flows began to increase toward the end of last month the counts dropped to as low as 603 this past Saturday. They revived a bit, rising to 2,238 on Tuesday and the tally was 1,746 on Wednesday. On Thursday, which included the special Bonneville operations, the count climbed to 2,506.
The Thursday operation at the “run-of-the-river” hydro project – which has little storage capacity – resulted in the elevation of Bonneville’s reservoir by as much as three feet. Much of that elevation gain was reversed by the end of the day.
The Columbia River Inter-Tribal Fish Commission’s Tom Lorz, who represents the Umatilla Tribes at TMT meetings, said the elevation rise is “worrisome” because of its potential to damage tribal set nets now in place for subsistence harvest.
Representatives of the four states said the operational experiment was worth a try. None of those participating in Wednesday’s TMT meeting objected to the flow cutback, which was scheduled from 5 to 9 a.m. Thursday.