Hetch-22

Some environmentalists want to remove the O'Shaughnessy Dam:

Initially protected by the establishment of Yosemite National Park, in 1913 the city of San Francisco won congressional approval to build the O’Shaughnessy Dam which buried this extraordinary wilderness valley [the Hetch Hetchy Reservoir] under 300 feet of water. Although John Muir was unsuccessful in preventing this from happening, his rigorous campaign resulted in the creation of an international environmental conservation movement. Modern engineering advances afford us the opportunity to remove the reservoir and create one of the most ambitious and exciting environmental restoration projects in human history. As a living laboratory, Hetch Hetchy will advance the science of restoration by providing biologists, ecologists and botanists from all over the world with the chance to apply cutting-edge science to re-establishing lost habitats.

A few points:

1. How would "lost habitats" in a valley that's been buried "under 300 feet of water" for a century be able to be "re-establish[ed]" in the first place? It's not as if we can turn back the clock and undo what's been done. (Time travelers excepted.)

2. According to this source, the Hetch Hetchy water system supplies 100% of San Francisco's water and much of the water in other places in the Bay Area:

3. However, I've read Restore Hetch Hetchy proponents argue it's not 100% but only 25% of the water to San Francisco. (Or maybe they mean 25% of the stored rather than supplied water.) But couldn't even a 25% reduction have quite a significant impact on the city?

4. If not under normal conditions, then what about during a major crisis? What if an earthquake hits the Bay Area? That's not improbable in California. Isn't the Big One overdue?

5. Anyway, if the dam is removed, wouldn't this mean San Francisco and other Bay Area cities would have to find a new water source? How realistic is this?

6. On a practical note, this measure should cost a not-so-insignificant amount of money if it goes through. More public money invested in more studies. But California isn't exactly in the healthiest fiscal state at the moment, to put it mildly.

7. What does it say when even prominent liberals like Nancy Pelosi, Dianne Feinstein, Barbara Boxer, and the mayor of San Francisco Edwin Lee oppose this? In fact, the mayor bluntly stated: "Their initiative is insane and attempts to fool voters into wasting millions to restudy local water sustainability projects that are already being implemented in San Francisco."

8. Not that I'd want to see it happen but it'd be ironic if these environmentalists got their wish, got rid of the dam, and San Francisco as well as much of the Bay Area dried up as a result.