Fish-friendly solutions

A close-up image shows a young salmon being introduced to the testing pool close to the jet nozzle. The High-velocity stream helped scientists understand why fish are commonly injured by hydroelectric dam turbines.

Although turbines have generated power at hydroelectric dams for many years, not much is known about how water flowing through the turbines may harm fish. In efforts to design more "fish-friendly" turbines, Pacific Northwest National Laboratory researchers conducted laboratory experiments to examine the relationship between water velocities within the turbine chambers and injuries to fish.

In the experiments, Chinook salmon were individually launched through a tube into a fiberglass testing pool. They were then introduced to high velocities of water pumped out of an underwater jet nozzle. Fish response to the water jet was digitally recorded through viewing windows located on the side and bottom of the testing pool.

Within a few seconds following each individual experiment, the pump was turned off and fish were captured using nets. Each fish was examined to assess the type and severity of external injuries. Injuries typically result from the rapid change of velocity over a small distance, also know as shear. Common shear-induced injuries include eye damage, gill damage, scale tearing, split fins, and bruising.

Video images of exposed fish were captured using high-speed, high-resolution digital cameras and 3-D motion analysis to measure the velocity, acceleration, jerk, bending angle, and bulk force of the fish. Recording these parameters helped scientists understand the injury process and dynamics.

With this study, researchers will be able to draw conclusions about how fish are injured during exposure to severe water forces. These data contribute to the development of improved engineering design tools and a promising new generation of turbines--resulting in increased fish survival rates.