‘Deadbeat dams’ and their impact on cold-water ecosystems

As California mulls water storage, a new study adds nuance to cold-water conservation.

 

As drought-stricken California considers constructing new dams, a new study finds that many of the state's existing structures despite efforts to prioritize healthy water temperatures are failing the cold-water ecosystems that depend on them.

The study, published in PLOS One, crunched data from 77 cold-water streams across California to characterize their “thermal regime” — that is, their annual temperature fluctuations over an eight- to 12-year period. Salmon, trout and a variety of other cold-water species are sensitive to disruptions in temperature patterns; the temperature range is as important to their life cycle as the amount of water flow. But across the state, the study found, certain dams disrupted these rhythms for up to 31 miles (50 km) of the rivers involved.

Pine Flat Dam in Sanger, California, releases water back into the flow of the Kings River after being held in a reservoir. Except for Shasta Dam, no other regulated river in a recent study showed the natural temperature patterns that cool- and cold-water ecosystems need.
George Rose/Getty Images

In order to protect habitat, water managers deliver cold water to streams from reservoirs. But according to lead author and UC Davis researcher Ann Willis, no one temperature can ensure the health of an ecosystem. For example, the temperatures required for the incubation of salmon eggs are different from what is needed for the fishes’ juvenile growth. “Streams are the temperature they are because of interactions between the water, the trees, the snowmelt and the groundwater creating unique temperature patterns,” she said. “Water temperature is so much more than a single number.”

Willis’ research highlights a difficult reality for conservationists: Out of 27 dams, only one successfully duplicated the crucial temperature patterns that the cold-water ecosystems depend on. “In science, when we have results like that, we call it an outlier, which means it’s the exception that proves the rule,” said Willis. Dams — even those designed to manage cold-water ecosystems downstream  were overwhelmingly unable to mimic the fluctuating temperature patterns.

Historically, water management has focused on releasing water from dams with a single-degree temperature target, or a seven-day average, to maintain cold-water ecosystems. But this simplifies the temperature dynamics, flattening an otherwise dynamic process and disrupting the seasonal patterns important to ecosystems. In other words, the right temperature isn’t always released at the right time.

Scientists and policymakers need to carefully consider thermal regimes when weighing the future of California’s water infrastructure and imperiled cold-water ecosystems, said Belize Lane, a hydrologist at Utah State University who was not involved in the study. “They make a good point: We have oversimplified environmental management targets.” But a more thorough study of the complex stream-level dynamics is necessary, Lane said, especially the potential role the state’s existing dams play in supporting the ecosystems’ temperature needs.

“They make a good point: We have oversimplified environmental management targets.”

Restoring a dynamic annual temperature pattern is crucial, both for preserving California’s salmon and trout — three-quarters of which are at risk of extinction — and for protecting the broader ecosystems that many Californians rely on. Whether that comes with — or without — dams is another question.

Some argue that dams can help manage cold-water ecosystems in a changing climate by storing and releasing cool water. But Willis said the science is clear: Environmental management needs to move away from oversimplified temperature targets.

Watershed management, as a field, has seen its operational strategies called into question before. After scientists noticed the importance of a varied amount of water flow, managers adjusted the timing and volume of water releases. The same holds true for temperature, said Willis: Adjustments need to be made to account for the patterns of cold-water streams and the species that depend on them.

Willis said she is not advocating the removal of all dams. She simply believes that we need to be more deliberate about what our water infrastructure seeks to accomplish. As she put it, we need to identify “deadbeat dams” — and remove them if necessary — while improving existing infrastructure as needed. If we want to enhance the ecosystems that so many species depend on, Willis said, we need to focus more clearly on how science informs our goals.

Increased water storage is on the list as federal infrastructure spending winds its way towards California. Willis hopes that her research will give pause to anyone recommending the expansion of the state’s already staggering dam footprintShe also cautions against relying on the existing approach to sustain cold-water ecosystems: “The science doesn’t support that,” she said.

Theo Whitcomb is an editorial intern at High Country News. We welcome reader letters. Email him at [email protected] or submit a letter to the editor. See our letters to the editor policy.

High Country News Classifieds
  • A CHILDREN'S BOOK FOR THE CLIMATE CRISIS!!
    "Goodnight Fossil Fuels!" is a an engaging, beautiful, factual and somewhat silly picture book by a climate scientist and a climate artist, both based in...
  • DIGITAL ADVOCACY & MEMBERSHIP MANAGER
    The Digital Advocacy & Membership Manager will be responsible for creating and delivering compelling, engaging digital content to Guardians members, email activists, and social media...
  • DIGITAL OUTREACH COORDINATOR, ARIZONA
    Job Title: Digital Outreach Coordinator, Arizona Position Location: Phoenix or Tucson, AZ Status: Salaried Job ID Number: 52198 We are looking for you! We are...
  • DESCHUTES LAND TRUST VOLUNTEER PROGRAM MANAGER
    The Deschutes Land Trust is seeking an experienced Volunteer Program Manager to join its dedicated team! Deschutes Land Trust conserves and cares for the lands...
  • ASSOCIATE DIRECTOR OF DEVELOPMENT
    The Nature Conservancy in Wyoming seeks an experienced fundraiser to join our team. We're looking for a great communicator who is passionate about conservation and...
  • INDIAN COUNTRY FELLOWSHIP
    Western Leaders Network is accepting applications for its paid, part-time, 6-month fellowship. Mentorship, training, and engaging tribal leaders in advancing conservation initiatives and climate policy....
  • MULESHOE RANCH PRESERVE MANAGER
    The Muleshoe Ranch Preserve Manager develops, manages, and advances conservation programs, plans and methods for large-scale geographic areas. The Muleshoe Ranch Cooperative Management Area (MRCMA)...
  • ARTEMIS PROGRAM MANAGER
    Founded in 1936, the National Wildlife Federation (NWF or Federation) is America's largest and most trusted grassroots conservation organization with 52 state/territorial affiliates and more...
  • ASSISTANT OR ASSOCIATE PROFESSOR OF ENVIRONMENTAL HUMANITIES
    Assistant or Associate Professor of Environmental Humanities Whitman College The Environmental Humanities Program at Whitman College seeks candidates for a tenure-track position beginning August 2023...
  • ANNUAL FUND MANAGER
    Working closely with the Foundation's leadership, the Annual Fund Manager is responsible for the oversight and management of the Foundation's annual operating fund. This is...
  • DATABASE ADMINISTRATOR
    Looking for someone who loves public land and understands the value and importance of data in reaching shared goals as part of a high-functioning team....
  • EXECUTIVE DIRECTOR
    High Country Conservation Advocates (HCCA) in Crested Butte, CO is seeking an enthusiastic Executive Director who is passionate about the public lands, natural waters and...
  • ASSOCIATE DIRECTOR OF VOLUNTEER PROGRAMS
    Are you passionate about connecting people to the outdoors? The Pacific Crest Trail Association (PCTA) is looking for someone with volunteer management experience to join...
  • EXECUTIVE DIRECTOR
    The conservation non-profit Invasive Species Action Network seeks an executive director. We are focused on preventing the human-caused spread of invasive species by promoting voluntary...
  • NEW BOOK: A FEAST OF ECSTATIC VERSE AND IMAGERY
    Dynamic fine art photographer offers use of images to raise funds. Available for use by conservation groups. Contact at www.anecstaticgathering.com.
  • WANTED: TALENTED WRITER
    Write the introduction to A Feast of Ecstatic Verse and Imagery, a book concerning nature and spirituality. Contact at www.anecstaticgathering.com. Writer who works for conservation/nature...
  • MT STATE DIRECTOR- THE WILDERNESS SOCIETY
    The Montana State Director is a member of The Wilderness Society's (TWS) Conservation program team who plays a leading role in advancing the organization's mission...
  • HIGH COUNTRY NEWS EDITORIAL INTERNS
    High Country News, an award-winning magazine covering the communities and environment of the Western United States, is looking for its next cohort of editorial interns....
  • THE MAGICAL UNIVERSE OF THE ANCIENTS: A DESERT JOURNAL
    Bears Ears, Chaco Canyon, and other adventures in the Four Corners area. 60 photos and lively journals. Purchase hc $35 or pb $25 from bigwoodbooks.com...
  • DIRECTOR OF PEOPLE AND ORGANIZATIONAL CULTURE - HR
    Career Opportunity: Director of People and Organizational Culture Do you have interest in approaching organizational culture from a place of creativity and curiosity? Do you...