Nearly 400,000 fish have migrated downstream past Round Butte Dam in Oregon since the beginning of 2010, indicating that the selective water withdrawal tower installed in the reservoir behind the dam in late 2009 has successfully restored fish passage from the Upper Deschutes River Basin.
By Steven Corson
As of August 2012, more than 397,000 fish had been passed downstream around the Pelton Round Butte Hydroelectric Project on the Deschutes River in Oregon. This large number is due to operation of a selective water withdrawal tower in the reservoir behind Round Butte Dam, which began operating in December 2009. Before the tower began operating, fish passage around the project had been blocked since the late 1960s.
Even more encouraging, on May 25, 2011, the first returning adult upper basin fish was captured at the fish trap below the Pelton Round Butte project, signaling that a fish marked and released in the Upper Deschutes Basin as the selective water withdrawal tower was installed had begun completing the migratory cycle, journeying to the Pacific Ocean and returning as an adult.
Later fish were marked using passive integrated transponder tags. With state and tribal authorization beginning in June 2012, more than 40 of these returning fish have now been transported above Round Butte Dam to complete their life cycle in the upstream tributaries where they were released as fry beginning in 2007.
|The selective water withdrawal structure installed in the reservoir impounded by Round Butte Dam has allowed migration of nearly 400,000 fish since it began operating.|
Designing and building the tower
This selective water withdrawal tower was designed to combine fish collection, water flows for power generation and downstream temperature management. It draws water from both the warmer surface layer and the cold bottom layer of Lake Billy Chinook, the reservoir impounded by Round Butte Dam. The structure changes surface currents to attract fish to the collection facility, lowers the temperature in the lake to provide healthier conditions for fish and allows management of the temperature in the lower Deschutes River where it exits the hydroelectric project to more closely match conditions that would be expected if the project were not there.
The structure also provides water to the three turbine-generator units in the 338-MW powerhouse at Round Butte Dam and uses turbine flow, not pumps, to create currents that draw fish to the facility.
Round Butte is one of three dams and hydro facilities in the 465-MW Pelton Round Butte Project on the Deschutes River. From upstream to downstream, the facilities are: Round Butte, 108-MW Pelton and a 19-MW reregulating dam. Portland General Electric is majority owner and operator of the Round Butte and Pelton dams. The Confederated Tribes of the Warm Springs Reservation of Oregon are PGE’s co-owners on the project and wholly own the reregulating dam.
Before the tower was built, fish passage facilities at Round Butte Dam (completed in 1964) consisted of a downstream surface collector, fish ladder and transport hopper system. These facilities were intended to provide both upstream and downstream passage for chinook, steelhead and sockeye. However, confounding surface currents in the Round Butte Dam forebay made it nearly impossible for fish to find the juvenile bypass system.
As a result, in 1966 PGE abandoned use of the juvenile and adult fish passage facilities at the project. To mitigate the effects of a lack of fish passage, in 1968 PGE began funding a hatchery program administered by the Oregon Department of Fish and Wildlife. Under this program, the Round Butte Fish Hatchery was constructed at the base of Round Butte Dam.
As its original Pelton Round Butte Project operating license from the Federal Energy Regulatory Commission neared expiration, PGE considered potential relicensing issues and began work in the mid-1990s to design a system that would both meet downstream temperature requirements and provide for fish passage. Then, in June 2005, as part of the process of renewing the FERC operating license, PGE and the tribes – which acquired an ownership share of the project in 2002 – agreed to spend $130 million for fish-related projects over the course of a new 50-year operating period.
There are two goals with regard to operation of the selective water withdrawal tower. The first is to create surface currents within the forebay that will help attract migrating summer steelhead, spring chinook and kokanee/sockeye smolts. The second is to return the temperature of water downstream in the Deschutes River to conditions that would be expected if the dams and reservoirs were not there by allowing withdrawal of water from various levels in the reservoir.
Installation of the selective water withdrawal tower began in the fall of 2007. All three major pieces were assembled on construction barges in the forebay and then set in place.
The 273-foot-tall structure cost $108 million to build and is divided into three sections. The bottom section, which is submerged to 270 feet deep and anchored directly in front of the powerhouse intake, is 70 feet tall by 60 feet wide. The middle section of the structure is a 40-foot-diameter vertical steel conduit that is 135 feet tall and connects the bottom and top sections. The top section, which separately sends water to the powerhouse and collects fish, is 60 feet tall, 90 feet wide and 150 feet long.
The water selection feature allows operators to draw cooler water from the bottom of the lake to mix with warmer water as needed to modify temperatures at the outflow downstream and approximate water temperatures that would be expected without the project in place.
At the intake structure, fish are collected into two V-screens and sorted by size. Larger fish (such as bull trout and kokanee) are returned to the lake. Smaller fish are further sorted and tagged on an adjacent floating fish transfer facility about 150 feet from the top structure, near the west shore of the lake. Juvenile salmon and steelhead are then loaded into a truck for transport and released downstream from all three dams to continue their migration to the Pacific Ocean.
Overall, results have been good, but variations have been seen. For example, catch rates of both chinook and sockeye salmon were substantially higher in 2011 than they were during 2010, but sockeye catch rates were then substantially lower than expected in the spring of 2012. This is a reminder that fish runs can vary significantly from year to year, depending on food supply, predation, growth rates and various other habitat conditions.
The standard for safe downstream passage at the new fish facilities is 93% for the first three to five years and then increases to 96% during the remaining license period.
Barnard Construction Company Inc. of Bozeman, Mt., was the general contractor for construction of the selective water withdrawal tower. CH2M Hill of Bellevue, Wash.; EES Consulting of Kirkland, Wash.; and ENSR/AECOM Technology Corp. of Redmond, Wash., designed the tower in collaboration with PGE Engineering. Thompson Metal Fabricators Inc. of Vancouver, Wash., fabricated the structure.
In addition, Dix Corp. of Spokane, Wash., provided expertise in marine construction and deployment. Associated Underwater Services of Spokane provided divers for underwater assembly of the structure.
In 2007, the Low Impact Hydropower Institute certified the Pelton Round Butte project as low-impact hydropower based on an array of environmental protection measures that included the selective water withdrawal tower. At the time, this was the second largest project ever designated by LIHI.
Portland General Electric and the Confederated Tribes of the Warm Springs Reservation of Oregon won an Outstanding Steward’s of America’s Waters award from the National Hydropower Association in 2011 for design and implementation of the selective water withdrawal structure and fish collection facility. This award recognizes the best example of hydropower’s ability to generate clean, renewable, reliable and affordable electricity while protecting the riverine ecosystem.
PGE also was named winner of the domestic Edison Award given by Edison Electric Institute in 2011 for completion of the tower. This award is presented annually and recognizes electric utilities for their innovation and role in advancing the industry.
In addition, the project received the American Council of Engineering Companies’ Grand Award in 2011. This award is given to engineering feats that exhibit uniqueness; technical, social and economic value; complexity; and success meeting project goals.
This fish tower has proven to not only be an effective way to transport fish but also takes into consideration the size of the fish being moved, making sure the smaller fish are able to make their downstream migration past the facility.
The results speak for themselves. Migratory fish are safely passing through the Pelton Round Butte Hydroelectric Project, and some of those fish have later returned upstream. This is a sign that the new system of fish transport is giving the river’s salmon and steelhead populations a strong change of growing over time and returning to upper basin tributaries as healthy, harvestable, sustainable runs that coexist with power generation, agriculture and other uses of the river system.
Bennett, Walter N., Vince Rybel, Mike Jenkins, Kerry Donohue, Richard E. Riker and Doug Sticka, “Retrofitting a Deep Water Plant Intake to Improve Fish Passage,” Hydro Review, Volume 30, No. 8, December 2011, pages 38-46.
In “Merrimack Village Dam: Results of Removing a Dam in New Hampshire” in the July issue, we incorrectly indicated that the dam had been removed in the photo on page 79. In fact, this dam was still in place at the time that photo was taken. Hydro Review editors regret this error.
Steve Corson is spokesman for Portland General Electric.