Salmon survival, cleaner hydropower focus of ORNL research
A new advanced turbine being tested at Wanapum Dam in Washington state produces nearly 5 percent more power, but before more are installed researchers at Oak Ridge National Laboratory are getting input from several thousand fish.
The project is part of an upgrade to a hydroelectric power plant owned by Public Utility District No. 2 of Grant County, and utility officials want to know how fish-friendly the new minimum gap runner turbine is compared to the 40-year-old turbine it replaced. Several Department of Energy Hydropower Program studies seek to answer that and other questions.
"Power company and DOE laboratory biologists are looking at direct mortality to fish caused by injuries during turbine passage, and theyre also attempting to assess indirect mortality," said Glenn Cada of ORNLs Environmental Sciences Division. "Even if a fish isnt killed immediately after passing through a turbine, it may become disoriented or physiologically stressed by the experience, and an apparently uninjured fish may fall easy prey to a predator or die later because of the passage stresses."
Indeed, the journey through a turbine isnt easy because fish are subjected to high pressures, shear forces, turbulence and possible mechanical strikes. Still, every year the vast majority of an estimated 2.5 million juvenile Chinook salmon and juvenile steelhead successfully make it through the 10 turbines at Wanapum Dam, located on the Columbia River. Nevertheless, DOE, Grant County officials and resource agencies want to further improve the odds, and theyre hoping that this project, one of the largest fish survival studies ever at a single hydroelectric dam, helps.
While the mortality rate of fish passing through conventional hydropower turbines ranges from 5 percent to 15 percent or more, the goal of DOEs hydropower program is to reduce these rates to 2 percent. Advanced turbines are approaching this goal by reducing turbulence, pressure changes and shear that occur within the turbine. The new minimum gap runner design at Wanapum Dam, however, has one more blade (six vs. five) and more wicket gates (32 vs. 20) than the older Kaplan turbine. So while the new design turbine generates more power, utility district officials want to ensure that there are no adverse effects on fish.
If the Federal Energy Regulatory Commission deems the fish passage survival rate through the new turbine acceptable, the utility district plans to replace the remaining nine units at a rate of one per year. Replacing the Kaplan turbines with minimum gap runner turbines could increase the electrical power rating of the Wanapum Dam from 895 megawatts to 940 megawatts.
In looking at indirect mortality, Cada and ORNL colleague Mike Ryon measure something called "C-start," or burst, swimming performance, a reflex behavior typically used by fish to escape predators. In this test, uninjured Chinook salmon that have passed through the turbine are rapidly transferred to shore, where their C-start behavior is filmed in the first minutes after exposure using a high-speed camera.
"This test allows us to evaluate whether a turbine-passed fishs predator avoidance behavior is compromised compared to the behavior of unstressed control fish," Cada said. "In addition, we are testing the hypothesis that the advanced turbine induces less sub-lethal stress than the conventional turbine."
A final report for the C-start behavior study will be complete by September.
In another ORNL-led study, Environmental Sciences Division researchers Mark Bevelhimer and Marshall Adams are examining blood and gill tissue from salmon that have passed through the turbine to determine the prolonged stress response to physical trauma experienced during passage through the turbine. Results will help researchers assess the level of general stress experienced by the juvenile salmon that have passed through the turbine, plus assess the rate of stress alleviation after a recovery period.
Meanwhile, Pacific Northwest National Laboratory researchers are developing methods to provide more complete information about the complex hydraulics of the turbine environment. They have tested a sophisticated "6 degree of freedom" sensor fish that they send through the turbine to gather information about water velocities, pressures and levels of turbulence. They expect this work to provide some of the first measurements of the fluid stresses experienced by fish passing through a turbine.
Another PNNL study involves immersing fish in a non-toxic dye that adheres to tissue that is exposed when a fish has been injured. Under particular wavelengths of light, the dye reveals injuries that might not be detected with the naked eye. Injuries revealed by the dye technique will be photographed and archived.
Depending on weather patterns, hydroelectric power accounts for between 7 percent and 12 percent of the electricity generated in the United States, but it plays a far bigger role along the Pacific Coast. There, it accounts for more than 50 percent of the electricity generated.
"One of the goals of the Department of Energy hydropower program is to find engineering solutions that will make the route of passage through turbines safer for fish," Cada said. "If we can accomplish that goal, hydropower will become a more acceptable form of clean renewable energy."
Ron Walli | EurekAlert!