News Release
| Release Number: | 99-048 |
| Dated: | 5/27/1999 |
| Contact: | Public Affairs Office, 503-808-4510 |
Portland, Ore. -- - Prototype tests of 40-foot-long screens at John Day Dam show more downstream migrating juvenile fish are guided into the bypass system, but also raise questions that need to be answered. These screens are being developed as a possible strategy to protect listed salmonids. Such screens have worked well at other projects.
Screens currently used in the juvenile bypass system to guide fish away from the turbines and into the bypass channel are 23 feet long. Research has shown that longer screens that extend further down into the turbine intake can be more effective at guiding juvenile fish away from the turbines.
Indications from 1996 tests show about 10 percent more of some species of migrating salmon entered the bypass system with the longer screens in place. Preliminary results from current tests with longer screens installed on Unit 7 at the dam also indicate guidance is improved.
While the guidance and timing results are very favorable, mortality rates are higher with the test screens in place. The longer screen's effects on lamprey moving through the dam also are being evaluated. The cause of mortality could range from turbulence, to debris, to being caught on the screens. The larger surface area of the longer screens creates more velocity and turbulence. Further tests of the system will be done to isolate the cause and biologists and engineers will work together to find solutions to those problems.
Some regional voices have called for pulling the screens and increasing spill to pass fish through the project. National Marine Fisheries Service (NMFS) and U.S. Army Corps of Engineers biologists, however, know that spill cannot be increased because it would raise gas levels in the river beyond safe levels. Steve Rainey, NMFS engineer, urged people not to give up on the screens yet because the extended screens intercept more fish, thus keeping them out of the turbines where mortality is higher. "The screens need to be judged on their overall passage survival benefit," he said, "and the jury is still out."
Once the higher mortality was noted with these test screens, additional research objectives were developed with the region to determine the cause for this problem. This is critical for the development of an improved screen design. The potential of longer screens to greatly improve juvenile survival warrants such effort.
Extended screen tests began two weeks ago and are expected to continue through July 17.
The Corps operates John Day Dam. Researchers from the Corps and the NMFS are conducting a series of detailed tests to determine the worth of longer screens for the dam's 16 turbine bays. The entire cost if the dam were fitted with longer screens would be about $40 million.
The screens are being tested at John Day, in response to NMFS 1995 Biological Opinion direction to test and, if tests indicate the prototypes work well, to install the screens. The System Configuration Team, the regional body which guides and prioritizes salmon recovery actions on the Columbia/Snake river system, toured the Columbia River projects last week and discussed the current tests. SCT members include the Bonneville Power Administration, U.S. Army Corps of Engineers, Bureau of Reclamation, NMFS, U.S. Fish and Wildlife Service, and the Northwest Power Planning Council and state fish and wildlife agencies.