Pend Oreille Public Utility District contracted IIHR to provide hydraulic modeling and analysis to improve the design of fish passage structures for its hydroelectric dams, including Box Canyon. Since 1983, IIHR researchers have worked to reduce the number of salmon harmed by the harsh environment in the hydroelectric turbines or to the high levels of nitrogen absorbed by the river as water mixes with air after passing through the spillway.

IIHR constructed several large-scale physical models of major dams, including the Box Canyon Dam, to build and test proposed fish-passage structures before construction. The laboratory models complement IIHR’s advanced CFD capabilities to simulate performance of fish passage facilities.

The Numerical Fish Surrogate, a specialized computer simulation tool developed in collaboration with the U.S. Army Corps of Engineers, allows IIHR researchers to model and predict fish response to passage structures with increasing accuracy.

IIHR’s fish passage program has led to the construction of better-designed structures and a remarkable decrease in fish mortality.