A program that involves significant coordination between fish biologists and dam operators at several hydroelectric projects in the mid- and upper Columbia River has shown increasing success at keeping fall Chinook alive in their freshwater life stages.
Agreements in 1988 and 2004 have led to increased redd counts, better egg-to-smolt survival and adult returns that continue to meet goals in Hanford Reach. This stretch of river below Grant County Public Utility District's Priest Rapids Dam is often called the last free-flowing section of the Columbia River, and is highly productive habitat for the main-stem river's fall Chinook population.
"At each phase, there have been really marked improvements in survival," Peter Graf, Grant PUD river coordinator, told the Northwest Power and Conservation Council on May 17. "It's really encouraging to see. Everyone in the region has been really pleased with how this has worked out," he added.
The Hanford Reach Fall Chinook Protection Program involves managing flows at seven projects—from Grand Coulee Dam to Priest Rapids Dam—for nine months of the year, Graf said. It requires active cooperation and collaboration from the Bonneville Power Administration, along with Grant, Chelan and Douglas public utility districts. "We work on it together and figure out ways to make this whole program work while still providing viable power and doing everything we need to do in the region," Graf added.
Efforts to preserve and restore fall Chinook in the Hanford Reach began in 1988 with the Vernita Bar Agreement, the initial settlement in which hydroelectric dam operators at Priest Rapids Dam and above on the Columbia agreed to work together on a flow regime. Graf said under the agreement, they focused on the spawning period. They kept flows at specific elevations during spawning, surveyed the river elevation of redds after Chinook had spawned, and ensured flows were sufficient to keep the eggs wet until young Chinook fry emerged.
Graf said one of the biggest challenges is keeping flows low enough during spawning so there's enough water during the winter—when the river naturally recedes—to keep the redds submerged. "The goal here is to manage our flows during the spawning period so all the redds stay wet," he said. It can be challenging because fall is often a time with significant precipitation. Operators use a method called reverse load factoring, targeting flows of between 55,000 and 70,000 cfs during the daylight hours, when fall Chinook spawn. At night, they release water to make room for more water.
This flow pattern was discovered by biologists researching fall Chinook in the Hanford Reach, Graf said.
When spawning is complete, biologists survey the elevation level of redds, which sets the flow levels for the winter, resulting in flows of between 65,000 and 70,000 cfs. "In a sense, that's the simple part of the program, but it also requires the most coordination among the signatories," he said.
"That worked really well," Graf said. But soon after, other challenges downstream revealed that large fluctuations in the hydro-system water releases pushed juvenile salmon into side-water areas where they would become stranded and trapped as soon as river levels dropped.
In 2004, the dam operators agreed to the Hanford Reach protection program, which expanded the Vernita Bar accord protections. Expanded flow protections include the period after Chinook fry emerge from their eggs and remain in the river until they're ready to migrate downstream—from about mid-February to mid-June.
In this third phase, dam operators are careful not to fluctuate river levels too rapidly, to prevent stranding of emerging juveniles. "This took a while for us to really dial in," Graf said, adding, "A lot of these flow constraints are really challenging, and it took us some time to figure out how to really do this and do this well."
Every five years, the Pacific Northwest National Laboratory conducts a monitoring and evaluation of the Hanford Reach fall Chinook program to ensure the flow protections are having the desired effects, Graf said.
From 2004 through 2006, soon after the Hanford Reach agreement was reached, overall compliance to flow targets ranged from 64 to 77 percent. But each year since 2007 except one, at least 94 percent of the compliance targets were met. In the last 10 years, compliance has been between 98 and 100 percent.
Graf noted the flow regimes are not based on specific dates. "This program is unique in that each phase of the program is really dictated by the life stages" and not by the calendar, he noted. "Transitions are determined by the salmon," he added.
Completed in 1961, Priest Rapids Dam had an immediate impact on fall Chinook returns to Hanford Reach, Graf said. But since the mid-1980s, when studies on flow designs showed optimal flows for spawning and incubation periods, the escapement goal of 31,100 adult returns has been met nearly every year, he noted.
He said it's hard to compare the current success of fall Chinook survival with what their survival might be under natural river conditions. But compared to other populations that experience natural flows, he said, the egg-to-smolt survival is very high because the controlled flows prevent extremely high flows when scouring events can wash redds downstream.
Patty O'Toole, director of the Council's Fish and Wildlife Division, said that Grant PUD's project to protect fall Chinook has been embedded in the Council's Fish and Wildlife Program since the late 1980s and is a great example of how the program protects not just listed species but other populations and habitat that are affected by hydroelectric dams throughout the Columbia Basin. "We do a lot for endangered species, but our program is broader and is focused also on protecting nonlisted stocks," she said.