Synthetic Salmon Answer Questions on Conditions Inside Hydroelectric Dams

High water velocities, changing pressure, increased dissolved gas concentrations, and the presence of turbine blades: these are the potentially fatal conditions a salmon encounters as it navigates its way through the turbines of hydroelectric dams on its journey to the sea. Although less than 10 percent of the fish actually incur direct injuries, the rate is still unacceptably high to resource managers. To better understand the conditions that fish endure during passage, researchers at the Pacific Northwest National Laboratory (PNNL) – a facility operated by Battelle for the U.S. Department of Energy (DOE) – in a program supported by the U.S. Army Corps of Engineers (USACE), Bonneville Power Administration, and the DOE, have developed the sensor fish: a rubber-encased battery of sensors, shaped like a real juvenile salmon, that measures and records pressure, strain, acceleration, and other hydraulic parameters.

“This is the first time we’ve had something we can send through a severe hydraulic environment and get real data about exposure,” says Tom Carlson, PNNL researcher. The sensor fish are released upstream, directed through the turbines, and then, equipped with balloons that float them to the surface, are recovered downstream. The sensors provide accurate data about the rate and magnitude of pressures experienced during turbine passage and allow scientists to “see” what it’s like to experience shear force, a severe condition that occurs when different water velocities collide. Depending on the shear’s intensity, a fish may become disoriented, lose its scales, or be bruised or cut. These sublethal injuries are important, because they weaken the fish and make it more susceptible to predation.

“The mechanical fish is not a complete package,” says Carlson. “It gives us data, but we still have to make sense of the data.” To facilitate data interpretation, PNNL has built a test facility to simulate the environment. “If we obtain data we don’t understand, we can try to duplicate the experience through the test facility. It also provides a way to validate numerical modeling.”

After scientists have completed advanced feasibility testing on the prototype, they will focus on the manufacturability of the sensor fish, which is designed to use off-the-shelf components and standard engineering principles. “It could easily be commercialized,” says Carlson, “and has already generated a lot of interest.”

The issue of restoring endangered populations of salmonids and determining how best to mitigate impacts of hydroelectric dams on salmon survival is highly controversial in the Pacific Northwest, where hundreds of projects have been built ranging in size from small irrigation diversions to large storage projects like Hells Canyon and the Grand Coulee dams. The trade-off between our need for power and water and our need to protect our environment is a delicate balancing act. Hydroelectric dams generate some of the lowest cost electricity in the world and dams provide irrigation to millions of acres of farmland.

The DOE, USACE, Bonneville Power Administration, and researchers at PNNL hope the sensor fish may provide a better understanding of conditions inside turbines and how they might be operated or modified to provide a safer passage for juvenile salmon and steelhead. Carlson adds, “Any time you provide safer passage for fish, you increase the hydraulic efficiency of the turbines by reducing avoidable losses. It’s a win/win situation.”

For more information, please contact Tom Carlson at (503) 417-7567 or via e-mail at thomas.carlson@pnl.gov.