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The study helps identify where high-quality, cold-water habitat remains to help managers prioritize conservation efforts.

"It is no longer a good investment to put all our cold-water conservation eggs in a dam-regulated basket," said lead author Ann Willis, a senior staff researcher at the UC Davis Center for Watershed Sciences and a fellow for the John Muir Institute of the Environment. "We need to consider places where the natural processes can occur again."

The uncommon cold

Understanding where cold water is likely to stay cold is critical for conservation. But "cold" is more than just a number on a thermometer. The term represents the many factors that combine to create cold water capable of supporting aquatic ecosystems.

Water managers deliver cold water from reservoirs to streams to support aquatic life. But Willis said this assumes that all cold water is the same -- akin to giving blood to another person without understanding their blood type and health status.