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Flows in Place to Protect
Snake River Fall Chinook Spawners

by Mike O'Bryant
Columbia Basin Bulletin - November 1, 2002

Preparing for the arrival of spawning salmon downstream from its Hells Canyon Dam, Idaho Power initiated stable and even flows Oct. 14, just in time to ensure salmon redds will not be dewatered.

One week later biologists from the utility and the U.S. Fish and Wildlife Service, while surveying the Snake River below the dam, found 30 redds made by spawning fall chinook salmon.

Wild fall chinook were listed by the National Marine Fisheries Services as threatened under the federal Endangered Species Act in April 1992 after their numbers reached a low of 79 spawning fish in 1990.

When Idaho Power built nearly 50 years ago the three dams that make up the Hells Canyon Complex of Dams -- in order from downstream, they are Hells Canyon, Oxbow and Brownlee dams, accounting for 60 percent of the utility's electricity generation -- they effectively blocked much of the historic habitat where fall chinook spawned, said Paul Wagner of NMFS. Today spawning for those fish is limited to about a 50-mile stretch of mainstem river below Hells Canyon Dam.

Idaho Power, which initiated the salmon flow in 1993 to improve spawning conditions as a response to the listing, this year set the flow at a flat 8,700 cubic feet per second, 24-hours a day. The utility intends to hold the flow until early December, or until further surveys show that salmon are no longer spawning, according to Dennis Lopez of Idaho Power. The utility will then likely increase flows through the winter (depending on water volumes this winter) as it evacuates its upriver reservoirs in preparation for the spring snowmelt, while also continuing to ensure redds are watered through emergence of fry into April 2003.

Since Idaho Power began the flow program, the number of fish returning to spawn has risen and this year, according to NMFS biologist Ritchie Graves, the number of fall chinook spawning in the area could reach as many as 10,000 fish. While NMFS has some operational and water quality issues that Graves prefers to remain confidential because they are a part of the Snake River Adjudication proceedings, he did say NMFS favors Idaho Power's program. "We have always supported Idaho Power's fall chinook spawning program," he said. "It is good for the mainstem spawners downstream from the dams."

However, the increase in the number of spawners is also due to other measures taken and not all of those fish are wild: some are first generation hatchery fish, he said. One of those measures is a change in where hatchery operators release juvenile fish from Lyon's Ferry Hatchery near Lower Monumental Dam. The hatchery, operated by the Washington Department of Fish and Wildlife, is a lower Snake River compensation hatchery designed to compensate for the loss of salmon and habitat from construction of the four lower Snake River dams in the 1960s.

Fall chinook salmon at Lyon's Ferry are "consistent with the genetics of the wild population," Graves said, a necessary feature to support the Nez Perce Tribe's desire to supplement the wild stock with the hatchery stock to get the population restarted.

At one time, the hatchery released juveniles at Ice Harbor Dam, but at the tribe's request, that changed in 1995 when the hatchery operators began releasing fish into the Lower Granite reservoir and the lower Clearwater River. The idea is to get returning adult salmon to move further upriver to spawn and help rebuild the population, Graves said.

However, even with 10,000 salmon expected to spawn in the reach above the Lower Granite reservoir this year, Graves said it is difficult to "tease apart" the information to know if the wild population is actually growing, information that is crucial to eventually delisting the species. The determination whether the natural population is trending upwards, downwards, or is holding steady will eventually be determined by a Snake River Basin Recovery Team, he said.

Since its inception, the initial flow chosen by Idaho Power for the operation has varied between 8,500 kcfs and 13,500 kcfs, depending on existing and potential basin water volume. "This has been a low flow year," Graves said. However, even with the high number of returning adult salmon expected, he said it's reasonable to assume there would be enough habitat for spawning.

Idaho Power's fall chinook program is similar to the Vernita Bar Agreement established for fall chinook on Hanford Reach, but it's better because no redds are left dewatered, said Graves. Idaho Power's program was voluntarily adopted by the utility, according to Lopez. The Vernita Bar Agreement was reached between federal and state agencies and Grant County PUD, which owns Priest Rapids Dam.

Another difference between the two programs is that Idaho Power retains a flat flow 24 hours every day while fish are spawning, while Grant County PUD maintains a daily average daylight flow (this year it is about 50 kcfs), but often raises flow levels at night to generate more electricity. Known as reverse load factoring because generators will typically produce more electricity during weekday daylight hours to meet higher consumer demand for electricity, the operation sometimes results in dewatering redds salmon build during the higher water.

While surveying the mainstem Snake River from the air, biologists also found 37 redds in the Grand Ronde River and nine in the Imnaha River. The aerial search, which Idaho Power and the USFWS have been doing since 1991, is conducted six times, weekly from mid-October through November each year, Lopez said.

Beginning next week, biologists will also begin trolling a transponder with a video camera in deeper areas to look for redds they cannot see from the air. Lopez said the utility had always maintained that some salmon were spawning in deeper water.

Related Sites:
Idaho Power:
National Marine Fisheries Service:

Mike O'Bryant
Flows in Place to Protect Snake River Fall Chinook Spawners
Columbia Basin Bulletin, November 1, 2002

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