IIHR developed fully 3-D computational models for the Idaho Power Company to help fish pass safely through hydroelectric dams on the Columbia and Snake rivers. Water flowing over a dam can become supersaturated with gas as the water plunges to extreme depths below the dam. Fish exposed to water with elevated total dissolved gas (TDG) can develop the painful and often fatal gas bubble disease.

Recent work on the Hells Canyon Dam, which is set on the deepest canyon in North America, was designed to help the utility company meet state and federal regulations for water-quality standards, including TDG. Politano developed the first two-phase numerical model to represent the complex physics of a dam’s tailrace. Her model can also evaluate technologies designed to reduce TDG and protect fish. For instance, spillway flow deflectors designed at IIHR redirect spilled water horizontally to minimize supersaturation by forming a surface jet that prevents bubbles from plunging deep in the tailrace. The numerical model makes it possible to test these technologies before millions are spent to build them on the river.