Tailoring Dam Designs to Local Fish may Benefit Economies and Wildlife

The injuries marinelife sustain as a result in sudden changes in pressure - known as barotrauma - can be mitigated in the turbulent waters surrounding hydroelectric dams by modifying the design of turbines, according to a new study.

Fishes are in danger of suffering from barotrauma when they pass through a dam or when they're hauled up form the depths during catch-and-release fishing.

When passing through a dam, the change in pressure the fish experience can be equivalent to ascending the entire height of Mount Everest in a matter of seconds. For some species, the change in pressure is too great, and comes on too quickly, resulting in their death or injury.

Some dams make it easy for fish to pass over or around them, but in others the fish can wind up passing through the dam's internal structure, where they can be subjected to enormous and rapid drops in pressure, followed by rapid increases in pressure.

Fish manage water pressure with an organ called the swim bladder, which expands and contracts in response to water pressure.

When traveling through a dam, the sudden and intense changes in water pressure can cause a fish's swim bladder to expand as much as eightfold. Such a rapid expansion can lead to injury or death.

In parts of the world that rely both on the hydropower created by dams and the sustenance and economic benefits of fishing the dammed rivers, dams pose an interesting challenge.

"Hydropower is a tremendous resource, often available in areas far from other sources of power, and critical to the future of many people around the globe," said Richard Brown, a senior research scientist at the Department of Energy's Pacific Northwest National Laboratory and the lead author of a paper appearing in the journal Fisheries.

"We want to help minimize the risk to fish while making it possible to bring power to schools, hospitals, and areas that desperately need it," Brown said in a statement.

The researchers report that that by studying the fish populations that migrate through dams, it is possible to get an idea of what sorts of pressure variations the fish are capable of withstanding and make adjustments to the dam's turbines to lessen the impact to migrating fish.

"Can we reduce the impact of dams on fish, to create a sustainable hydropower system and ensure the food supply and livelihoods of people in these regions? Can others learn from our experiences in the Pacific Northwest? This is why we do research in the laboratory - to make an impact in the real world, on people's lives," said PNNL researcher Zhiqun Deng.