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Upstream of Bonneville Dam on the Columbia River in Washington State, Thomas Carlson tosses a handful of translucent plastic fish packed with electronic detection gear into the water. During their 15-second roller coaster ride through the dam's hydroelectric turbine, these virtual juvenile salmon endure bruising current flows and drastic swings in water pressure -- forces that kill tens of millions of six-month-old salmon each year on their return journey to the Pacific.
Downstream from the dam, the six-inch plastic piscines sprout six orange water wings and bob in the swirling water until Carlson and his team of researchers from the Pacific Northwest National Laboratory rescue them. Later, in the warmth of the lab, Carlson plugs wires into the fishes' tails and downloads important digital information. Recorded by tiny microprocessors and pressure gauges during the school's turbulent traverse, these data paint a real-time picture of the forces the young salmon suffer during their brief, crushing time inside the turbine chambers.
Carlson hopes such accurate measurements of the water conditions in the dam's turbines will help engineers design structures that are more fish-friendly. That could save millions of wild salmon and perhaps give a boost to both the increasingly endangered fish and the thousands of fishermen who depend on salmon for their livelihood.
DIGITAL SUBMERSIBLES. The Pacific Northwest and the Columbia River are synonymous with salmon. But that may change if the wild populations of fish continue to dwindle. Currently, 12 different species of the river's salmon and steelhead are listed under the Endangered Species Act. Since 1981, state and federal agencies have invested $3.1 billion to try to come up with technologies that could help rebuild the fish populations. One of these is Carlson's sensor fish.
These digital submersibles, molded from actual bodies of juvenile salmon, are shedding light on what scientists consider to be a key problem area for salmon survival. Research suggests that, more than any other factor, the Northwest's dams are responsible for the waning salmon numbers.
The dams block adult salmon from reaching their spawning grounds, although there are alternate routes through tributeries. Just as crucial, dams also block and slaughter salmon offspring on their downstream ocean run. Inside the turbines of hydroelectric dams, huge numbers succumb to direct strikes or massive internal injuries caused by the water pressure and currents induced by the spinning turbines.
$5,000 "FISH." "This technology will provide scientists with the first opportunity to measure actual environmental conditions in operating hydropower turbines at measurement scales directly applicable to juvenile fish," says Carlson. "We are learning more about how water turbulence and the turbine blades directly injure fish or disable them and make them more susceptible to predation," he says.
Last January, Carlson's group released the first school of nine sensor fish-- each costing $5,000 -- into the turbines of the Bonneville Dam. During their swims, each fish collected 96 kilobits of data, enough to run a small computer file or Java applet.
That might not seem like much data, but it has already proven to be enough to make a difference. Carlson's studies indicate that young fish tend to get trapped in the gaps of a turbine's blades, with about 10% getting killed in the effort to migrate. But when those turbines are redesigned to minimize the gaps, juvenile injury rates might be cut by 50%, and survival rates increase about 6%.
WIN-WIN SITUATION. This single-digit improvement, according to Carlson, means 5 million more juvenile fish will get to swim down river each year, on top of the 40 million to 45 million that are surviving now. And those extra 5 million fish could lead to an exponential growth in the population if more fish are able to return upstream to spawn. "It ends up being a huge number" of fish saved, he says.
Even better, Carlson's studies show that redesigning the turbines increases power output by about 4% for the same amount of water flow. And that means that the technology actually pays for itself. So it's a win-win situation for consumers buying power as well as salmon struggling for survival.
By Ellen Licking in New York Edited by Alex Salkever
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Copyright 2000, Bloomberg L.P.
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