California’s Crucial Reservoirs Are Running Low, And That’s Even Worse Than It Sounds

An ongoing drought has drained California dry

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The Hetch Hetchy reservoir is one of California's crucial reservoirs. Amit Patel

California is in the midst of an "exceptional drought." Exceptional might sounds a bit tame. But, according to the Unites States Drought Monitor, "exceptional" trumps “extreme” and “severe.” Exceptional is the worst.

Running on three years of low rainfall, California's now in a state of emergency. Last Friday, officials declared that no water would flow from California's complex system of state-run reservoirs to those downstream. The move, says the Associated Press, “affects drinking water supplies for 25 million people and irrigation for 1 million acres of farmland.”

“We are on track for having the worst drought in 500 years,” B. Lynn Ingram, a UC-Berkeley professor, told the New York Times.

The drought is threatening to push the unemployment rate as high as 50 percent in farm-heavy regions, says the AP, and is threatening the survival of creatures that live in the state's rivers.

And, says the National Oceanic and Atmospheric Administration, it doesn't look like the drought's going anywhere.

Whether climate change is contributing to the California drought is difficult to say. Researchers studying the 2012 Great Plains drought, which affected middle America, found that climate change was not to blame in that event.

But a recent study on the resiliency of California's water system found that low water conditions in the state are likely to increase as the world warms. The scientists looked not just at how temperatures would affect rainfall and snowmelt, but also at how California's water system—its rivers and dams and reservoirs and political systems—would handle drought. In some ways, the study suggests that the current drought is a portent of things to come.

The researchers found that, as the world warms and snow melts earlier each year, the peak flows into the system will move up in the calendar, as well. The total amount of available water will also be lower than we're used to, says Tara Garnett, at the Public Library of Science's blog. “The water supply was also estimated to drop incrementally with each temperature increase, though it is somewhat cushioned by the availability of water stored in California’s reservoirs," she writes.

In their study, the researchers emphasized the role of California's reservoirs in modulating the water supply to the state:

When interacting with the modeled representation of the managed water system, the impacts manifest as decreased water supply reliability and lower reservoir storage volumes. Thus, while system attenuation of the climate change signal may occur through the capacity of large reservoir and conveyance systems to buffer altered hydrology, with modeled operation regimes unchanged, temperature-driven warming and its influence on modeled hydrology translates into decreased surface water supply reliability in these basins.

If the state's reservoirs are the last bastion buffering climatic variaibility, that makes Friday's claim that the reservoirs are too low to have any water to spare even more alarming.

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