Low flows, dry winter could spell trouble for Crooked River fish

November 9, 2018
Low flows, dry winter could spell trouble for Crooked River fish

Managers must balance water storage for irrigation against the needs of fish

By Stephen Hamway

It could be a tough winter for redband trout and other fish living in the Crooked River, thanks to a decision to hold more water in Prineville Reservoir Earlier this fall, the U.S. Bureau of Reclamation announced that it planned to release 50 cubic feet of water per second from Bowman Dam, a 57-year-old dam on the Crooked River that forms Prineville Reservoir.

During dry years, water managers have a mandate to balance water storage for irrigation seasons with the needs of fish. The practice is part of a multiyear plan to retain water in the reservoir.

“If we use it now, we won’t have it later,” said Bridget Moran, supervisor for the Bend field office of the U.S. Fish and Wildlife Service.

But with less water in the reservoir than usual and another dry winter looming, some conservationists are concerned that the fish may be getting shortchanged, and may see dramatic population declines over the winter.

“The only thing we can do is hope for a lot of rain,” said Yancy Lind, a blogger and fisheries activist in Central Oregon.

The stretch of the Crooked River just below Bowman Dam is popular among fishermen, due to its populations of redband trout and mountain whitefish. Brett Hodgson, Deschutes district fish biologist for the Oregon Department of Fish and Wildlife, said the section of the river is also an important corridor for the reintroduction of Chinook salmon and steelhead into portions of the Deschutes Basin.

Over the last four years, water management in the area has been governed by a 2014 law stating that roughly half of Prineville Reservoir’s approximately 148,000-acre-foot capacity must remain in the river for fish, with the other half going to irrigation districts.

The city of Prineville receives a small amount of water from the reservoir. An acre-foot is the amount of water necessary to cover an acre of land with a foot of water.

However, Hodgson said the irrigation districts have first access to the water in question. In dry years, when the reservoir doesn’t fill entirely, less water is left in the river for fish, which reduces food supply and habitat for fish that call the river home.

Hodgson added that releasing 90 cubic feet per second — roughly 40,000 gallons of water per minute — is the lowest amount to create optimal habitat for redband trout and other fish. When the water level drops much below that, Hodgson said it can constrict fish and the insects they eat, increasing competition between fish in the river and driving numbers down.

“You’re limiting the amount of available habitat for fish to sustain themselves in the river,” he said.

The Bureau of Reclamation, after consulting with representatives from local, state and tribal governments, along with other federal agencies, determines how much water to release from the reservoir during dry years. The agencies look at attributes, such as how much precipitation is expected during the winter, and how full the reservoir is, according to Gregg Garnett, manager of the Bend field office of the Bureau of Reclamation.

As of Thursday evening, Prineville Reservoir was 35 percent full, well below average for early November. The reservoir never filled during the spring, and likely won’t again this year, Lind said.

Additionally, long-range forecasts are calling for a warm, relatively dry winter in much of Central and Eastern Oregon. In October, the National Oceanic and Atmospheric Administration declared that it is more likely than not that an El Nino weather pattern will form over the Pacific Ocean.

Garnett wrote in an email that the bureau originally hoped to release 65 cubic feet per second, but revised that prediction based on how dry the year has been.

Moran added that 40 percent of the water left in the reservoir is there because of savings from prior years.

“We would love to be up at 80 CFS this year too,” Moran said. “We’ve had to make hard choices.”

However, the approach has caused problems for fish in the past. During the winter of 2015-16, a shortage of water forced the Bureau of Reclamation to cut the amount of water released to 35 cubic feet per second for a 50-day period, according to a 2016 report from ODFW.

That period corresponded with a cold snap that caused portions of the river to freeze, which further reduced fish habitat. In total, redband trout populations in that portion of the river declined by 87 percent from 2015 to 2016, and mountain whitefish declined by 45 percent.

“It was an unfortunate set of circumstances, to say the least,” Hodgson said.

Hodgson doesn’t anticipate a similar drop-off this winter, but said a “modest reduction” in redband trout could occur. He added that the low flows could impact salmon and steelhead as well, though its harder to know where in the Deschutes Basin the fish will travel to.

Lind acknowledged the gamble could pay off, but he said it would likely require a better-than-anticipated snowpack. More broadly, though, he criticized water managers for not properly accounting for a changing climate and dragging their feet on systemic changes. Any meaningful change would likely come from the Deschutes River Basin Habitat Conservation Plan, a long-term, multiagency plan expected out in draft form in 2019, Lind said. Until then, Lind said he expects water shortfalls to continue.

“We’re talking about re-arranging deck chairs on the Titanic,” he said.

— Reporter: 541-617-7818, shamway@bendbulletin.com

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