The water level in the Crooked River took a dramatic drop this week after dam operators cranked down the gates at Bowman Dam due to drought conditions that produced historic low levels in Prineville Reservoir.
The reduced flow will make it difficult for fish to survive until more water becomes available in November.
As of Friday on the Crooked River, about 35 cubic feet of water per second was flowing out of the dam, down from a level of 180 cfs on Wednesday when the ramp-down effort began. The flow is expected to continue to drop to around 10 cfs, said Bruce Scanlon, general manager for the Ochoco Irrigation District.
Scanlon, the general manager for the past four years, said the ramping down marks the end of the irrigation season for his district’s 900 patrons. He does not discount unusually low water levels seen in the reservoir.
“The magnitude of this historic situation — and its impacts on not only farmers, (but also) fish, wildlife, and recreators — is huge,” said Scanlon. “It’s an economic impact. It has environmental impacts across the board. It’s a situation none of us ever wanted to be in.”
The 125-mile-long Crooked River is a tributary of the Deschutes River, running mainly through Crook County. Parts of the river are protected under the National Wild and Scenic Rivers System. It’s popular among kayakers and is well-known as a fishery for steelhead, brown trout, and native rainbow trout.
But the river, like others in Central Oregon, has been in trouble in recent years due to historic drought conditions that have left much of Crook County bone dry.
Prior to the construction of Bowman Dam in 1961, the Crooked River would commonly fall to around 10 cfs or lower by late summer, according to Kyle Gorman, region manager for the Oregon Water Resources Department. But since the construction of the dam, the river had never before fallen to 10 cfs in September.
Scanlon said irrigation season normally ends in mid-October, and Crooked River levels drop to 50 cfs to support fish and aquatic life. This year, the 50 cfs level will resume on Nov. 1, according to the U.S. Fish and Wildlife Service. That leaves about six weeks for fish to survive in dramatically low river level conditions.
Some storage water is being held back to provide “pulse flows” to occur in the river in the late winter and early spring to assist chinook and steelhead smolts migrating out of the Crooked River system.
The drop in water level means an early end of water deliveries for around 900 Ochoco Irrigation District patrons who grow hay and other crops in the Prineville area. But Scanlon said it could have been worse had the spring rains not arrived.
“We were blessed this year with the May and June rain and runoff that helped us extend the season because prior to that we thought we would be done almost two months earlier. So I think we are looking at the bright side of shutting off water now rather than two months ago,” said Scanlon.
But the low flow in the Crooked River has raised alarm bells among Central Oregon’s angling and naturalist community.
Anglers, flyfishing groups, fishing guides, birders, and naturalists have contacted the Oregon Department of Fish and Wildlife in recent weeks to express concern over the long-term health of the river, said Jerry George, district fish biologist with the agency.
George said he is also “extremely concerned” for the health of redband trout and mountain whitefish fisheries below Bowman Dam. At 10 cfs, he said, water quantity and quality will be reduced to levels that could pose an acute threat to fish and aquatic species.
“We are in uncharted territory here,” said George.
The main concern is that cold water from the bottom of the lake, which typically supports fish downstream, will be unavailable this fall.
In normal years, the cold water supports a productive tailwater fishery for trout and whitefish. It also produces an important holding, spawning, and rearing habitat for spring-run chinook salmon and summer steelhead.
The low levels have prompted ODFW to encourage catch-and-release anglers to avoid fishing during the 10 cfs period or to fish during cooler morning hours to minimize stress.
“We have heard from many local guides that plan to not take clients to fish the Crooked River during the 10 cfs period,” said George.
ODFW reports that a minimum summer discharge of 140 cfs and winter minimum discharge of 90 cfs is necessary to provide sufficient habitat to support “robust” salmonid populations in Crooked River below Bowman Dam.
When river levels drop, the result is the creation of pools that trap fish, restricting their seasonal movement to different habitat. George explains that this causes increased competition, stress, and disease transmission, and can lead to widespread mortality of fish in the river.
The low flows also impact the wider ecosystem, he said, reducing macroinvertebrate production, an important forage base for Crooked River fish.
Scanlon said his district has consulted with ODFW during the ramp-down process on how to mitigate risk for fish.
“As we ramp down and decrease flow we are trying not to strand fish and to give them opportunities to seek places to hole up,” said Scanlon. “So we are following ODFW guidance in ramping procedures to allow that to happen.”