Preliminary data suggests the new fish facility at central Oregon’s Round Butte Dam can sweep in significant numbers of salmonid smolts so that the young fish can be given a ride around the hydro project and two other dams to be released downstream.
Between 25 to 50 percent of the chinook smolts and 12 to 24 percent of steelhead smolts PIT-tagged last year found their way down the long arms of Lake Billy Chinook to the dam, aided by a developing current created by a selective water withdrawal tower that now stands upstream of the dam.
And those numbers should only climb higher as round-the-clock water withdrawals establish a new water temperature regime and current in the reservoir, Portland General Electric researcher Megan Hill said last week during a two-day workshop in Madras. Researchers gathered there to review results of research and project implementation related to Deschutes River subbasin fish and habitat restoration.
The Deschutes and two of its tributaries, the Crooked and Metolius rivers fill Lake Billy Chinook, which is backed up by Round Butte. One of the major focuses in the basin is the reintroduction of spring chinook and steelhead above the Pelton-Round Butte complex of three dams. Chinook and steelhead were extirpated in the upper Deschutes watershed soon after construction of the three dams in the 1960s. The dams control flows in the lower 100 miles of the Deschutes River.
Original dam construction included a fish passage system; however, due to bottom withdrawal, confusing reservoir currents in Lake Billy Chinook and temperatures it did not attract smolts to the forebay and fish transfer facility.
The 140-foot-tall tower is changing all that. It is designed to selectively draw cold water from the bottom of Lake Billy Chinook and warm water from the surface during different parts of the year to meet downstream water temperature and quality requirements. The water withdrawal are also intended to a create a cooler reservoir that should be healthier for fish and a surface guidance current to attract migrating young salmon and steelhead into the tower’s floating top structure, which is a fish collection facility.
The Crooked, Deschutes, and Metolius river arms comprise 23 percent, 26 percent, and 51 percent of the total lake surface area, respectively. The respective length of each arm is 6.5, 8.7 and 12.1 miles.
Hill said it could take as long as four years for the reservoir regime shift to be fully completed. This year and in the next years the draw toward the tower should become stronger.
Hill, Cory Quesada, and Micah Bennett conducted migration research in the first year of the tower’s operation. The $108 million structure was cranked up for the first time in December 2009. During that first year nearly 100,000 juvenile anadromous fish — including 50,000 kokanee, 42,000 spring chinook and 7,800 steelhead smolts — were transferred downstream to continue their migration to the Pacific Ocean.
The research, which is ongoing, seeks to monitor the outmigration of chinook and steelhead from their release in the tributaries, through the reservoir to the tower and to points downstream such as Bonneville Dam on the lower Columbia River. The Deschutes feeds into the Columbia between The Dalles Dam (the next dam upstream of Bonneville) and John Day dams. The study also aims to develop smolt production estimates (how many survived from the fry stage) for each tributary, evaluate the size and growth of the young fish and chart their migration timing, travel times and migration routes.
Another focus of the research is to evaluate survival rates from the tributary streams across the reservoir to the fish collection facility and the facilities collection efficiency.
In anticipation of fish passage, chinook and steelhead fry have been outplanted in the Metolius, Crooked and Deschutes rivers and tributaries since 2007.
As part of the study the researchers captured and PIT-tagged 1,686 chinook and 536 steelhead smolts in the upper tributaries in the spring of 2010. In addition, 52 steelhead were radio-tagged in the Crooked River (river kilometer 62).
The highest survival in 2010 was for hatchery chinook smolts tagged in the Crooked River and recaptured at the fish collection facility, at 50.5 percent. That accomplished one of the initial goals of the salmon/steelhead introduction program -- to capture at least 50 percent of the smolts of one species (spring chinook, steelhead or kokanee/sockeye salmon) from one of the three major tributaries to Lake Billy Chinook.
The Metolius survival total for PIT-tagged chinook was 29.2 percent and the Deschutes chinook survival to the collection facility was 24.3 percent.
For steelhead, survival was 24.2 percent down through the Crooked River arm and 11.5 percent down the Deschutes arm.
The 2010 data shows that smolt size varied by tributary. Chinook captured in the Crooked River system were significantly larger than chinook captured in the Metolius or Whychus creek, a tributary to the Deschutes. Crooked River and McKay Creek steelhead were similar in size, but significantly smaller than steelhead captured in the Deschutes arm.
PIT-tagged chinook grew an average of 0.58 millimeters (about 0.02 inches) per day between the times of PIT tagging and recapture at the collection facility. Steelhead grew an average of 0.80 millimeters per day.
The chinook grew an average of 1.4 inches from the time they were trapped in the tributaries to when they got to the collection facility and the steelhead grew about 1.1 inch on average.
The chinook migration in the Crooked and Metolius rivers peaked during the last two weeks in March. Chinook caught at the collection facility increased significantly the first week of April. There were two large pulses of chinook at the FTF, one the first week of May and one the first week of June.
Steelhead had shorter travel times through Lake Billy Chinook than chinook, traveling an average of 2-3 kilometers per day. Chinook in the Crooked River were significantly faster than fish tagged in the Metolius or Whychus Creek. Naturally-reared chinook moved through the reservoir faster than hatchery Chinook used as part of the study. Travel time decreased for both chinook and steelhead later in the migration season