I have a very emotional attachment to the National Parks, particularly Yosemite.
Back in the 1920's, Yosemite's twin valley, Hetch Hetchy was dammed up and is now under 300 feet of water. It's now determined that it would be feasible to deconstruct the dam and return the valley to it's pristine condition.
But the cost would be $10 billion dollars. Environmental groups say it could be less.
Other water storage facilities are available in other dammed areas downstream. Alternative sources of electricity for the Bay Area would be needed. But conservation and clean energy like wind power in the Altamont Pass is possible.
A Hefty Price Tag on Restoring Hetch Hetchy - Los Angeles Times
The damming of Hetch Hetchy is the worst example of taking a part of a National Park for something other than what the National Parks were created for.
The restoration has been called for since the mid 1980's when Reagan's secretary of the Interior, Don Hodel, thought it should be done. Senator Feinstein who apparently thinks Yosemite should just be for San Francisco, is against any attempts to take down the dam.
It was a terrible mistake to drown a beatiful valley with waterfalls and granite cliffs just like Yosemite Valley. Other sources of water and power are available. I'd like to see Hetch Hetchy in my lifetime and not in a boat.