Dams Ineffective for Cold-Water Conservation

Study of California Streams Reveals Fish Give Dams the Cold Shoulder

  • by Kat Kerlin
News
Aerial view of Shasta Dam with mountains in background
Shasta Dam, north of Redding in California, is the only dam in the state a study identified as being capable of replicating natural cold-water patterns for aquatic species. (Ron Lute/cc BY-NC 2.0)

Quick Summary

  • Knowing where cold water is likely to stay cold is critical for conservation. But “cold” is more than just a number on a thermometer. Dams do not adequately support cold-water ecosystems.

Dams poorly mimic the temperature patterns California streams require to support the state’s native salmon and trout — more than three-quarters of which risk extinction. Bold actions are needed to reverse extinction trends and protect cold-water streams that are resilient to climate warming, according to published in the journal PLOS ONE by the University of California, Davis. 

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 , a senior staff researcher at the 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.”

Woman scientist stands in stream with monitoring equipment with male scientist in background
Ann Willis, a researcher with the Center for Watershed Sciences, takes measurements on the Little Shasta River with colleague Rob Lusardi in 2017. (Joe Proudman/)

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. 

While previous studies have suggested that dams can be operated to achieve ideal temperatures, few tested that hypothesis against the temperature patterns aquatic ecosystems need.

The  study assessed stream temperature data from 77 sites in California to model and classify their “thermal regimes,” or annual temperature patterns. It found the state’s reservoirs do not adequately replicate natural thermal patterns, making them incapable of supporting cold-water species effectively.  

“I’m an engineer; I thought we could operate ourselves into success, but the science doesn’t support that,” Willis said. “It’s not a question of whether we remove a dam, but which dam, and how we need to restructure how we manage water. Or we need to be willing to take responsibility to be the generation that says, ‘OK, we’re letting this ecosystem go extinct.’” 

What about the drought? 

Drought often tempts people to double-down on hard-infrastructure solutions for water storage.