A university study finds that warming streams could exterminate spring-run Chinook salmon in California by the end of the century unless management options are adopted that would affect hydroelectric generation.
The University of California, Davis, released results of study Sept. 1 by scientists at UC Davis, the Stockholm Environment Institute, and the National Center for Atmospheric Research that was funded by the Environmental Protection Agency.
Staff of the UC Davis Center for Aquatic Biology and Aquaculture used a model of California's Butte Creek watershed, taking into account dams and hydropower plants along the river, combined with a model of the salmon population, to test the effect of different water management strategies on the Endangered Species Act protected fish. They fed in scenarios for climate change out to 2099 from models developed by NCAR in Boulder, Colo.
UC Davis said in almost all scenarios the spring-run Chinook died out because streams became too warm for adults to survive the summer and spawn in the fall.
"The only option that preserved salmon populations, at least for a few decades, was to reduce diversions for hydropower generation at the warmest time of the year," a statement by the university said.
However, the study noted summer also is the peak season for energy demand in California. Director Lisa Thompson of the UC Davis center, said it might be possible to generate more hydropower upstream while holding water for salmon at other locations.
"The goal should be to identify regulatory regimes which meet ecosystem objectives with minimal impact on hydropower production," David Purkey of the Stockholm Environment Institute's Davis office, said. "The kind of work we did at Butte Creek is essential to seeking these outcomes."
Thompson said there are options that remain to be fully tested, such as storing cold water upstream and releasing it into the river during a heat wave.
"That would both help fish and create a surge of hydropower," the statement said.
A hydro project on Butte Creek, the 26.4-MW DeSabla-Centerville project, has been under fire for several years by environmental and fishing groups that contend low stream flows, warm water temperatures, and pathogenic outbreaks on Butte Creek have killed thousands of salmon in summer and early fall before they had a chance to spawn.
DeSabla-Centerville (No. 803) is licensed by Pacific Gas & Electric Co. It operates in run-of-river mode, diverting flows from two reservoirs and from Butte Creek through a series of powerhouses and canals and returning flows to Butte Creek. The Federal Energy Regulatory Commission, NOAA Fisheries and PG&E have been involved in talks to protect spring-run Chinook since at least 2002 as part of efforts to relicense DeSabla-Centerville.