Environmental groups contend that the Bonneville Power Administration’s shift to wind turbines buttresses their case for tearing down dams in the agency’s territory, particularly four along the lower Snake River in Washington State that helped decimate one of North America’s great runs of wild salmon.

Bonneville wants to keep all the dams, arguing that they not only provide cheap power but they also make an ideal complement to large-scale installation of wind power. When the wind slows and power production drops, the agency argues, it can compensate quickly by telling the Army Corps of Engineers and the Bureau of Reclamation, which operate the dams, to release more water from reservoirs to turn the huge generators. When the wind picks up, dam operations can be slowed.

The dams help alleviate a need for natural-gas-fired power plants, which are used in other regions as a backup power source when the wind stops blowing, but which release carbon dioxide that contributes to global warming.

By balancing wind power with hydropower, the Bonneville Power Administration says it believes it can limit the use of natural gas and coal plants across the West, even as the region’s demand for electricity rises. Around the country, dams provide 6 percent of electricity generation  double the amount from other renewable sources like wind, solar power and biomass  and much of that is concentrated in the West.

The influx of wind on Bonneville’s system has come as a result of renewable power goals set by governments in the Western states, which aim to reduce their output of greenhouse gases. Bonneville says that when the wind is blowing most strongly, 18 percent of the power in its control area now comes from wind, and that number may rise to 30 percent next year. (Not all of that is consumed in the Pacific Northwest; some is sold to California.)