Climate change must receive serious consideration as officials contemplate whether to relicense hydroelectric projects throughout California, advises a watershed scientist at UC Davis.

“Given the rapidity of climate warming, and its anticipated impacts to natural and human communities, future long-term (typically 30-50 years) fixed licenses of hydropower operation will be ill prepared to adapt if possible hydrologic changes are not considered,” wrote Joshua Viers, associate director of UC Davis’ Center for Watershed Sciences, in a recent issue of the Journal of the American Water Resources Association. (The paper is available online at: http://watershed.ucdavis.edu/pdf/Viers_JAWRA_2011.pdf .)

Viers warns that shifts in precipitation, combined with an increase in energy demands as temperatures rise, could dramatically impact hydropower production.

According to the California Energy Commission, hydropower — predominantly fueled by Sierra Nevada snowmelt — provides approximately 11 percent of California’s in-state energy production.

But while hydropower is considered a source of cleaner energy — one that could help reduce climate-altering greenhouse gas emissions — it is vulnerable to climate warming.

For example, if annual temperatures rise 4 degrees Celsius (about 7 degrees Fahrenheit), summer seasonal hydropower production is projected to decrease by up to 30 percent for hydropower facilities in the American, Bear and Yuba watershed, according to a study led by the Stockholm Environment Institute and co-authored by UC Davis scientists. (The paper is available online at: http://www.iwaponline.com/jwc/002/jwc0020029.htm .)

This vulnerability was not taken into account when the Federal Energy Regulatory Commission recently approved study plans for relicensing of the Yuba-Bear Drum-Spaulding hydroelectric facilities in Northern California.

Failing to consider climate change research is “poorly reasoned and risky,” says Viers.

The western Sierra Nevada currently has 54 hydropower projects licensed by the commission. These projects include dams, powerhouses and 826 kilometers of water conveyances such as ditches, canals and tunnels. More than 1,800 kilometers of rivers run downstream from these projects, representing 53 percent of all regulated rivers in the western Sierra Nevada.

This hydropower infrastructure not only represents a huge economic investment, but also highlights the need to consider adaptive solutions to water and ecosystem management, hydropower generation and climate warming as snowmelt flowing through hydroelectric plants diminishes.

“If the Federal Energy Regulatory Commission is to establish conditions of operation for 30-50 years,” Viers says, “licensees should be required to anticipate changing climatic and hydrologic conditions for a similar period of time.”

Funding for this study was provided by California Energy Commission.