"When I lived in Mountain View (between '83 and '91), there was an attempt to wreck the Hetch Hetchy very similar to this one. It was bitterly opposed by environmental groups who pointed out that the loss of this reservoir would mean the need to replace it by innumerable water projects which would cause much more damage to the environment than would be mediated by the restoration of the original terrain."

Well I live near Yosemite around that time and I know there was environmentalists who hated Hetch Hetchy and wanted dam drained- it was as though it was a blight upon their souls.

Of course it would environmental nightmare to drain it, not mention all around a stupid idea.
After arguing about it for while I got the impression what was really missed was the river to go kayaking down. I think some teacher somewhere probably spent hours mourning the loss of his youth or something- I believe same one had field trips having to do saving some mountain goat.

Web search:
"Was there opposition to building the dam?

John Muir led the fight to preserve Hetch Hetchy Valley. Dozens of organizations and newspapers nationwide opposed the dam, but they were defeated by San Francisco."
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"What will be the effects on whitewater rafting and fishing downstream of the dam?

Without the dam, there will be some periods in the spring where flows are too high to raft. But a new flow release regime would in fact greatly extend the whitewater rafting and kayaking season, and increase recreational opportunities.

Minimum fish releases would remain in place. A more natural water flow cycle will occur below Hetch Hetchy Valley than occurs today. Furthermore, six miles of premium trout stream will be restored in Hetch Hetchy Valley."
http://www.hetchhetchy.org/faq.html
"Who is in favor of removing the dam?

Many major conservation groups support a study of dam removal, and support removing the dam if feasible water and power supply replacements can be found. These include the National Wildlife Federation, Environmental Defense, Natural Resources Defense Council, and Sierra Club. Local Native Americans support a study of dam removal; they are particularly concerned that their ancient sites be protected once the dam is removed."
http://www.hetchhetchy.org/

"The Yosemite Association had this article online:

S.F. Use of Hetch Hetchy Studied

City doesn't need the Yosemite reservoir, grad student says

"Since conservation icon John Muir lost the fight against O'Shaughnessy Dam in 1913, environmentalists have been waiting for this moment. It's an opportunity to re-evaluate the need for the reservoir.

The Sierra Club, Environmental Defense, Restore Hetch Hetchy and others consider O'Shaughnessy a monumental mistake. They have believed all along that San Francisco could live without Hetch Hetchy Reservoir."
http://faculty.deanza.edu/donahuemary/stories/storyReader$961