Hanford Reach Flow Protections Help Keep Fall Chinook Healthy, Productive
- July 17, 2020
- John Harrison
A program to manage Columbia River flows to protect Fall Chinook salmon that spawn in the Hanford Reach of central Washington is helping keep that population, also known as upriver brights, productive, healthy, and harvestable.
It wasn’t always that way. In fact, before agreements in 1988 and 2004, fluctuating river levels caused by hydropower operations varied widely, ranging from 36,000 to 150,000 cubic feet per second. This caused Fall Chinook egg nests, called redds, to become exposed and juvenile salmon to be stranded along the margins of the shoreline.
Studies conducted in the early and mid-1980s, ultimately lead to the 1988 Vernita Bar Agreement, which provided specific protection for spawning adults and incubating embryos. The 2004 agreement added protections for juveniles emerging from the gravel and rearing along the margins of the shoreline, thereby providing protections for all freshwater life stages of the fish.
Hanford Reach Fall Chinook lay their eggs in the fall. The eggs incubate over the winter, and tiny juvenile fish emerge in the spring and are carried downriver to the ocean. Low and variable flows in the winter can expose eggs laid in the fall, causing them to dry out and die, and high and variable flows in the spring can wash juvenile fish into the sand and grass along the shore, stranding them out of the water when the river recedes.
It was problem with a variety of power-production, environmental, and economic dimensions. It needed solving.
“Multiple parties came together under challenging circumstances to address the issue,” said Tom Dresser, fish and wildlife manager for Grant County Public Utility District, in a presentation at the Council’s July meeting. Grant PUD owns and operates the first two of seven hydropower dams above the Hanford Reach in the United States, Priest Rapids and Wanapum. The most prolific spawning area in the Reach, Vernita Bar, is just downstream from Priest Rapids Dam.
“We all had different ideas and visions, but over time with the best available science and adaptive management, we’ve been able to develop and implement a plan to protect Fall Chinook in the Hanford Reach while also allowing hydropower operators to continue to produce and deliver affordable energy,” Dresser said. “This demonstrates how parties coming together and working together can get to a successful program.”
The parties that worked to develop the program comprised a diverse group, including representatives from the utilities (Bonneville Power Administation, Chelan PUD, and Douglas PUD), state and federal fish and wildlife agencies (NOAA-Fisheries, WDFW and USFWS) and tribal representatives from the Yakama Nation and Colville Confederated Tribes. Other participating entities included the Columbia River Intertribal Fish Commission, Alaska Department of Game and Fish, and the Wanapum People.
Before the dams were built, river flows naturally declined in the fall and winter and increased in the spring and early summer. The hydropower system changed that, increasing flows in the fall and winter with the demand for electricity. Today, flows are still variable, but fluctuations are better controlled and a minimum average flow of 70,000 cubic feet per second is generally targeted during the months that the fish spawn, the eggs incubate, and juvenile fish emerge and rear before heading for the ocean.
Biologists monitor the Reach, and the dam operations commence when the fish begin to spawn. The goal is to keep the eggs underwater. As well, dam operations are modified to account for the fact that Chinook lay their eggs during daylight. Target flows typically around 70,000 cubic feet per second are delivered during the day. Water held back during the day to ensure the target flow is met is released at night.
“A neat feature of this program is that the operations are determined by the fish, not the calendar,” said Peter Graf, a fisheries scientist with Grant PUD. “We protect the redds once the fish start spawning. Water temperatures drive the development of eggs. So every year the timing is a little different.”
This requires carefully watching the river and the fish.
“The sweet spot for the redds is determined by flows and depth of the river,” Graff said. “Over the winter, flows naturally recede, but without close management, flows in the fall can be higher than in the winter. So the goal is to manage flows to keep the eggs underwater for the winter.”
The dam operations continue into the spring, when the juvenile Chinook emerge from their eggs. Overall, it’s working.
“Generally what we found from researchers is that the program has provided benefits to fish,” Graff said.
Paul Hoffarth, a biologist with the Washington Department of Fish and Wildlife, said 87,651 Fall Chinook returned to the Reach in 2019, and the estimate for 2020 is 92,700.
“This population has been holding strong,” Hoffarth said. “Between the flow protections in the fall and the control of fluctuations in the spring, we are continuing to meet our escapement goals and managing the population as very healthy.”
That’s important to the state, but also to fisheries in the North Pacific Ocean. The fishing opportunity has a significant economic value to local communities and to the commercial fishing industry.
“The Hanford Reach Fall Chinook support fisheries all the way to Alaska,” he said. “We average about 27,000 angler trips for Fall Chinook in Washington annually; it’s a huge fishery, all supported by these healthy returns. We are able to provide lots of opportunity that would not be there without the protections in the Hanford Reach.”