California Will Lose Hydropower Capacity As Climate Warms

Shasta Dam | Photo: Andy Paterson/Flickr/Creative Commons License

An assessment of the effects of California's changing climate projects that existing hydroelectric generating facilities will be unable to keep up with demand for power. The report, "Our Changing Climate 2012, Vulnerability & Adaptation
to the Increasing Risks from Climate Change in California
" released today by the California Energy Commission (CEC) and the Climate Change Center, is the third statewide assessment of California's future in a warmer world. And the outlook for our hydroelectric infrastructure isn't rosy.

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Statewide temperatures rose 1.7° between 1895 and 2011. California is expected to gain 2.7° in the first half of this century. Expected effects include more frequent large storms, greater demand for electrical power on hot days, and increased wildfires.

Despite the likelihood of stronger storms, California reservoirs may well find themselves with a shorter water supply on average. California's historic water supply system for both power generation and drinking water storage was built on the assumption that most of the state's usable precipitation falls in winter as snow in the mountains. Snowmelt has recharged the reservoirs each year, and managers could anticipate the next year's supplies by measuring snowpack.

Three quarters of California's hydroelectric power is supplied by "high-elevation" facilities built above 1,000 feet in elevation. These facilities typically have small reservoirs, and are thus quite vulnerable to reduction in output due to reduced snowpack. Many of these hydropower facilities are in the Sierra Nevada, the region in California where warming has been the most marked. The report forecasts significant reduction in power output from these high-elevation plants during hot summer months, when demand for electricity is greatest in California.

Compounding this problem is the greater likelihood of wildfires brought about by climate change. Climate is linked to wildfires by a variety of factors, ranging from warmer winters that kill fewer bark beetles to drier conditions overall to increased prevalence of summer lightning storms. Burned-over landscapes like those surrounding reservoirs in the Sierra Nevada can erode catastrophically after damaging fires, and silt washed off burned landscapes will inevitably find its way into reservoirs, reducing the state's hydroelectric capacity still further.

Wildfire Risk to Transmission Lines. | Image: Courtesy California Energy Commission

Increased likelihood of wildfires will also make the power distribution system far more vulnerable, especially in the mountains near Los Angeles and the crucial northeastern corner of the state, our link to the reliable hydropower of the Pacific Northwest. Even in the absence of fire, an increase in hot days will increase the electrical resistance of the transmission lines, by as much as 7-9%.

The report points out that reliance on our current system of long-distance power transmission will become increasingly risky as those transmission lines become ever more vulnerable, and suggests microgrids and distributed generation as a possible remedy to this vulnerability.

The report was conducted by the CEC and Climate Change Center under the auspices of the California Environmental Protection Agency, as directed by a Executive Order signed by Arnold Schwarzenegger in June 2005 that requires periodic science reports on the potential impacts of climate change on the California economy.

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