So now we have to have a vote on tearing down Hetch Hetchy . That's fine, let's have the discussion. But let's be honest about it: This isn't just, or even primarily, a water issue. It's really about electric power.
If you want to read the piece I wrote on this for Earth Island Journal, it's here.  I've written loads more over the years , enough to fill a couple of good-sized books. But let me try to make the point as simply as I can.
The dam would never have been approved by Congress if it were just a reservoir for San Francisco's water. The reason the Raker Act, which authorized the destruction of Hetch Hetchy Valley, was approved was that the conservationists, who opposed the dam, were trumped by the public-power advocates, who argued that preventing private companies from controlling the electric power grid was so important that it justified environmental sacrilege. The dam was supposed to provide the centerpiece for a local public-power system that would prevent Pacific Gas and Electric Company from controlling the city's energy system.
The history of Hetchy Hetchy isn't about water -- it's about how that power never made it to San Francisco. You can read it in great detail here . I have spent weeks in the National Archives in DC researching this, and have thousands of pages of documents on it. You may or may not support the idea of the city running a public-power system, but it's hard for anyone to argue that Congress intended anything else.
The city accepted the deal, built the dam, and has for almost a century ducked, bobbed, weaved, and tried everything possible to avoid kicking out PG&E.
So why keep the dam in place? I don't believe the Restore Hetch Hetchy people when they say that the city can find other storage for its water needs. Tear down the dam and we'll be sucking water out of the Delta soon enough. But forget that -- let's assume we could conserve enough water that we didn't need that reservoir.
We'd still have to replace a buttload of electric power. The city's hydropower system generates 1.7 billion kilowatt hours a year, enough to power more than 400,000 homes -- and does so without producing an ounce of CO2. Although there are other powerhouses in the system, we'd lose almost half of its capacity if we tore down the dam.
It seem to me that existing large hydro, while imperfect, is a more environmentally sound form of electricity generation than coal, oil, natural gas, or nuclear -- and right now, those are the alternatives.
Soon enough the city will have enough small-scale distributed generation, mostly rooftop solar, to get rid of both PG&E and the dam. Count me as a supporter. But we're not there yet.
In the meantime, if we're going to have this discussion, let's talk about electricity, and PG&E, and the Raker Act, not just water and the once-pristine valley.