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California Plumbing: A Mind-Boggling Web

More than 1,400 dams and diversions provide graphic proof of the human footprint on California's watersheds. These barriers, some dating back to the Gold Rush, provide water storage, hydropower and flood control for millions of Californians. But dams are highly controversial because of their impact on the environment.

California has hundreds of dams

There are 1,404 dams in California, ranging from six-foot structures damming small creeks, to the towering Oroville Dam, at 742 feet the tallest in the country (Yes, Oroville is taller than Shasta and Hoover Dams).

Data from California Department of Water Resources, State and Federal Dams in 2010

Produced by Lisa Pickoff-White

Only some produce electricity

There are more than 130 hydropower projects in the state. Projects can include multiple dams and powerhouses. Depending on the year, up to 17 percent of the power generated in California comes from hydropower but California does not count large-scale hydro as "renewable energy."

Map from the California Energy Commission

But 'dam' few rivers remain undeveloped

How many undammed rivers remain in California? It depends on whom you ask. After speaking to several experts, we came up with a short list, including the Smith, the Clavey, the South Fork of the Trinity and the Mattole.

According to Ron Stork, senior policy advocate for Friends of the River, only one river in the state is undammed from source to ocean: the Smith River, tucked up in the northwest corner of California near the Oregon border.

But the Smith isn't the only answer we got.

"The Cosumnes is the only major river that I know of that does not have a major dam on it," said Eli Ilano, deputy forest supervisor for the Tahoe National Forest, raising the question of what's considered a "major" river.

"There is a small dam on [the Cosumnes]," Steve Rothert, the California Director at American Rivers pointed out. "I think it's now sort of defunct, but it does have a dam on it." Instead, Rothert pointed to a small tributary of the Tuolumne. "Many people consider there to be one river that's not dammed in California, and that's the Clavey River."

Others suggested the Mattole in the Lost Coast and the South Fork of the heavily dammed and diverted Trinity River.

It all depends what your definition of "dam" is, said Jeanine Jones, interstate resources manager for the California Department of Water Resources. "There are some rivers that people conventionally speak of as being "undammed," but in fact have some small diversion dams on them."

It also depends on what your definition of "river" is.

"In some respects this issue is a little bit harder in California because of our very climate and the fact that we do have some rivers that are very wet and some that are basically ephemeral streams," Jones said.

"Anyway you cut it," said Stork of Friends of the River, "we dammed a heck of a lot of rivers."

Produced by Don Clyde and Lisa Pickoff-White


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Water and Power was produced by Climate Watch, KQED's initiative covering climate science and policy issues, with a specific focus on California.