Dams ineffective for cold-water conservation

Date:
August 25, 2021
Source:
University of California - Davis
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, finds a
new study.



FULL STORY ==========================================================================
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 a study 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 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.



========================================================================== 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 UC Davis 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.



==========================================================================
"We falsely equate dams with water security," Willis said. "More storage
does not mean more water. A giant, empty refrigerator doesn't help you
if you're starving. The same is true for water." Of California's 1,400
dams, only one very large and highly-engineered dam - - Shasta -- stood
out in the study as replicating natural cold-water patterns.

The study does not suggest removing all dams. However, considering
removing "deadbeat dams" where there are critical ecosystems could help
restore natural processes and support fish, people and biodiversity amid climate warming.

Cold comfort Key cold-water conservation candidates include streams highly influenced by groundwater, such as in the Cascade Range, and places
where water easily infiltrates the soil, such as Northern California's
Feather River.

"Classifying these streams and understanding their thermal regimes is
an effective way to focus our time and money on the places most likely
to make a difference," Willis said.

The study's co-authors include Ryan Peek and Andrew Rypel of the UC
Davis Center for Watershed Sciences.

Funding for this research was provided by internal support from the
UC Davis Center for Watershed Sciences and the John Muir Institute of
the Environment.

========================================================================== Story Source: Materials provided by
University_of_California_-_Davis. Original written by Kat Kerlin. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Ann D. Willis, Ryan A. Peek, Andrew L. Rypel. Classifying
California's
stream thermal regimes for cold-water conservation. PLOS ONE,
2021; 16 (8): e0256286 DOI: 10.1371/journal.pone.0256286 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210825143023.htm

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