When salmon swim through dam turbines, the changes in pressure can be catastrophic to their bodies. Researchers are trying to figure out how improve fish survival rates. And the U.S. Army Corps of Engineers is paying attention. Reporting for EarthFix, Courtney Flatt has more.
A small trailer sits outside Pacific Northwest National Laboratory’s new aquatic research center. The trailer houses four oval tanks. Each is about as wide as a basketball hoop.
Researcher Brett Pflugrath points out a balloon in one of the tanks. It represents a fish’s swim bladder. The swim bladder helps fish float up and down.
Pflugrath begins to raise and lower the atmospheric pressure inside the tanks. This mimics the pressure fish experience when swimming through a hydroelectric dam turbine. He raises his voice over the loud machines.
Plugrath: “If we increase the pressure, that balloon will actually get much smaller.”
As fish swim toward the dam, pressure increases. But as soon as they pass through the turbine blade, pressure drops dramatically in seconds.
This rapidly changing pressure is bad news for fish. It causes fish to experience something like the bends. Imagine if you rose too quickly from a dive. Or if your airplane cabin suddenly lost pressure. Then multiply that feeling about 50 times.
Researcher Richard Brown says says pressure changes differ depending on how deep fish are when they approach dams.
Brown: “This is very unique because this is the only system that can perform really rapid decompressions across the whole broad range of pressure changes.”
Brown says researchers can connect injuries they see in fish with different types of pressure changes.
Brown: “So when they build a new turbine, the pressure changes will be mild enough so that you won’t see injuries or mortality.”
Shawn Nelson is a project manager with the U.S. Army Corps of Engineers. He says engineers are using this research to design new turbines at the lower Snake River’s Ice Harbor Dam.
Nelson: “We are seeing efficiency improvements. We are seeing fish survival improvements. From an environmental perspective, it’s a sustainable option. And from a power perspective, we’re gaining power.”
Nelson says building and installing a turbine costs $20 to $25 million. The new turbines will likely be installed in 2015.
Copyright 2013 Northwest Public Radio