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Release: Dec. 5, 2000

UI engineers receive $2.15 million to help save the salmon

IOWA CITY, Iowa — Deep-sea divers know that the "bends" -- an excess amount of nitrogen in the bloodstream -- can be fatal, so they rise slowly to the surface in order to give their bodies time to expel nitrogen.

Similarly, baby salmon swimming at the base of hydroelectric dams on the Columbia River in the Pacific Northwest can get the bends from water that has crashed over spillways, taking nitrogen from the air and compressing it into the river water below. With a mortality rate approaching 50 percent, the salmon need help.

Enter a team of engineers from the University of Iowa's College of Engineering and Iowa Institute of Hydraulic Research (IIHR). Armed with $2.15 million in new funding from Public Utility District No. 2 of Grant County, Washington, the engineers are pursuing a variety of projects aimed at modifying the dams, including some that make use of an indoor, 100-foot-wide-by 160-foot-long scale model of a Columbia River dam and a one-mile length of the downstream waterway. So far, the engineers have used their Iowa City-based workshop -- one of the largest models of its kind -- to learn that deflecting water away from the base of the spillway and toward the river channel can reduce the amount of nitrogen in the water, resulting in a higher survival rate for the salmon. They are also using a computerized model to predict reductions in nitrogen gas that could result if certain modifications were made to the dam.

"No laboratory model can actually predict the total level of dissolved nitrogen in the water because of the model's reduced scale," says Larry Weber, assistant professor of civil and environmental engineering. "Therefore, if we can predict such nitrogen levels with our numerical model, we could reduce cost and time while improving design performance."

The entire research effort is an attempt to help mediate a long-running Pacific Northwest dispute over how to restore the salmon population. It pits environmentalists, who want to reduce hydroelectric flow or dismantle some dams outright, against the electric power industry and its dams, which provide about 75 percent of the region's power. According to Weber, the Iowa research, funded in the amount of more than $10 million over the past 16 years, will be worthwhile if it helps revitalize the Columbia River salmon fishing industry, which is valued at more than $1 billion. "We are trying to modify the nitrogen content in the water that goes past the dam in order to prevent the bends in the salmon," Weber says.

According to Dana Jeske, hydromechanical engineer with the Grant County Public Utility District, the state standard of 110 percent the amount of nitrogen normally present in river water

imposes limits on the volume of water that can be sent over the spillway. He notes that turbulence at the base of the spillway causes more nitrogen bubbles from the air to dissolve into the water. However the addition of deflectors below the spillway gates shoots water more rapidly downstream, resulting in lower nitrogen levels and a better water quality environment for the salmon.

"Can we economically get the fish out of danger? If so, the use of deflectors may be more cost effective than simply spilling the water past the dams," Jeske says. In any event, the success of the project will rest, in part, on measurements of the water downstream from the dam, where water currently diverted around the dam mixes with water sent through the dam.

One of the ways Weber and his colleagues are trying to determine whether the deflectors will work is through the use of their software, called U2RANS. Developed with the aid of a supercomputer at the National Center for Supercomputing Alliance, the software is providing detailed models of how different columns of water mix below the dam. So promising is the software that in the future, it may not even be necessary to build large-scale models to determine water flows.

Predicts IIHR researcher Jacob Odgaard: "One day we'll be able to use computers to simulate water flow and fish passage along the Columbia River almost the same way in which other researchers currently simulate driving down Interstate 80 or flying a 747 across the Pacific."

In addition to Weber and Odgaard, UI researchers working on the project are: V.C. Patel, professor and director of the Iowa Institute of Hydraulic Research; Yong Gen Lai, associate research engineer, Pete Haug, engineer 1; Fernando de Andrade, Heqing Huang, Paul Dierking, Scott Zimmerman and Troy Lyons, all graduate research assistants; Greg Hein and Nick Campney, undergraduate students; and several UI support staff members.