Study to test effectiveness of strobe light systems as a deterrent to resident fish entrainment
(Confederated Tribes of the Colville Reservation news release)
July 16, 2001
Nespelem, Wash. –
In an effort to deter resident fish species from entering turbines at Grand Coulee Dam and leaving Lake Roosevelt, the Confederated Tribes of the Colville Reservation announced today that a 5-week study to test an underwater strobe light system began June 30. Scientists from the Tribe, Pacific Northwest National Laboratory, U.S. Geological Survey and Bureau of Reclamation are conducting the work.
"This is an important study for the Tribe, and the entire region," said Richard LeCaire, the project manager for the Chief Joseph Kokanee Enhancement Project. "The Colville Tribe is committed to enhancing resident fish populations, but also understands the importance of hydropower to the region. This project is an important first step in testing what could be an extremely effective tool for enhancing resident fish stocks without affecting power generation-both at Grand Coulee and at other dams as well. We are pleased to be teaming with PNNL scientists in solving this complex technical problem."
Because construction of Grand Coulee Dam in the late 1930s blocked anadromous fish runs to the Upper Columbia watershed, efforts through the Northwest Power Planning Council (NWPPC) and Bonneville Power Administration (BPA) to mitigate these losses have been ongoing. One form of mitigation is resident fish programs. But when fish leave Lake Roosevelt, or are entrained, it adversely affects these programs.
Prior research conducted by the Colville Tribes Chief Joseph Kokanee Enhancement Project determined that entrainment at Grand Coulee Dam is significant and that 85 percent of the entrainment occurs at the dam's Third Power Plant. An estimated 402,000 fish per year are entrained through the turbines at Grand Coulee Dam. Once fish are entrained, their mitigation value to Lake Roosevelt is completely lost. The Tribe is attempting to reduce entrainment to maintain the success of the mitigation programs.
The system to be tested consists of a number of distinct components. Three powerful strobe lights manufactured by Flash Technology Corporation were loaned to the project by the Bureau of Reclamation's Denver office. These will be suspended below a barge in front of the dam's third powerhouse. Also attached to the light array are multi/split beam hydro-acoustic transducers. These function to track fish movement so Pacific Northwest National Labs (PNNL) scientists can observe how fish react to the strobe lights. Finally, a number of hatchery reared kokanee salmon and rainbow trout will have sonic tags surgically implanted. These tags will be tracked by sensors near the forebay area and allow the scientists to better understand how resident fish specifically react to the lights.
"We'll be running the study 24 hours per day, 7 days per week for about six weeks. Other studies have only tested the equipment at much smaller dams and on a smaller scale," said Bob Johnson, the PNNL fisheries biologist leading the field tests. "PNNL scientists have studied strobe light impacts on fish behavior previously and also used hydroacoustics to track fish behavior near surface bypass collectors at Bonneville Dam on the Columbia River and Lower Granite Dam on the Snake River. This project is a natural next step to combine this expertise to address a regional issue."
"We hope the system will keep kokanee and rainbow trout away from the turbines, keeping them in Lake Roosevelt where they will be accessible to subsistence and recreational fishermen. This is important for restoring resident fish populations, and will hopefully help recreation in the area as well," said LeCaire.
LeCaire added that the fish array may be visible from the shore, but should not affect recreation.
Tags: Energy, Hydropower