The Science of Sustainability

Hetch Hetchy: Will We Do the Anthropocene Thing?

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Hetch Hetchy Reservoir occupies Hetch Hetchy Valley behind O'Shaughnessy Dam. Photos by Andrew Alden

San Franciscans this fall will be asked to vote on the Water Sustainability and Environmental Restoration Planning Act, a scheme that aims to put the cost of civilization in sharp relief. In essence it asks, Do we want to arrange our society as if nature really matters?

Every great city relies on a great water supply, from ancient Rome to San Francisco. The Hetch Hetchy system was beautifully designed and built, except that it destroyed a nearly unique valley inside Yosemite National Park. The nonprofit organization Restore Hetch Hetchy (RHH) wants San Franciscans to weigh the price of doing things better, according to a specific definition that includes pulling out of the park.

The Hetch Hetchy Water System begins with a dam and reservoir that traps some of the world's cleanest water in a basin of Sierra Nevada granite.

The spillway next to O'Shaughnessy Dam has gates that are turned up in winter.

Tunnels and pipelines carry Hetch Hetchy water to the Bay Area entirely by gravity, with some of that gravitational energy turned to electricity along the way.

Hetch Hetchy water drives turbines at the Moccasin power plant south of Jamestown.

The Hetch Hetchy Water System is a colossal engineering triumph that has provided not just San Francisco, but many Bay Area cities, with clean and reliable water for nearly 90 years.

Hetch Hetchy Water System monument north of route 132 between Vernalis and Modesto.

The Hetch Hetchy Water System still performs to specifications, but RHH argues that today we could make it work while sparing Hetch Hetchy Valley and removing its reservoir. That may be so, and the few million dollars required for a good study and action plan would be well spent because previous efforts have been sketchy. RHH is rolling the dice by forcing the plan, whatever it is, to be considered by the San Francisco Board of Supervisors for placement as a charter amendment in the 2016 elections. That is, if the Supes vote it down, nothing will come of it, but if both they and the city's voters approve it the plan will go into effect willy-nilly.

Dam removal is a growing endeavor, and one of great scientific interest, because so many of the nation's dams are reaching the end of their lives. This happens when the reservoirs behind them fill up with sediment. The most recent success in dam removal is the Elwha Dam project in Washington state. In that case, the reservoir had silted up. O'Shaughnessy Dam is more than 30 times as large as Elwha, its reservoir is far from being silted up, and the dam isn't sited on an earthquake fault. From an engineering standpoint, there's no rush.

RHH's plan is a visionary scheme based on environmental justice, appealing as an example of eco-responsible, sustainable practice. But are we better off with the dam gone now? Conversely, if we really are in an "Anthropocene age" when we can influence the entire planet by our actions, shouldn't we begin to act accordingly? Shouldn't we begin geoengineering?

The obstacles to RHH's plan are great, but I believe the group is playing a very long game. The Hetch Hetchy system is exceptionally stable because the reservoir is many centuries away from filling up with sediment. As time goes on our ability to engineer the water system intelligently will only improve. As a geotechnical matter, that slow pace of sedimentation means that Hetch Hetchy Valley can indeed be restored. By putting the question to a formal evaluation, RHH hopes to ensure that restoration will be on the agenda for as long as it takes.

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Category: Blog, Engineering, Geology, Water

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Andrew Alden

About the Author ()

Andrew Alden earned his geology degree at the University of New Hampshire and moved back to the Bay Area to work at the U.S. Geological Survey for six years. He has written on geology for About.com since its founding in 1997. In 2007, he started the Oakland Geology blog, which won recognition as "Best of the East Bay" from the East Bay Express in 2010. In writing about geology in the Bay Area and surroundings, he hopes to share some of the useful and pleasurable insights that geologists give us—not just facts about the deep past, but an attitude that might be called the deep present. Read his previous contributions to QUEST, a project dedicated to exploring the Science of Sustainability.
  • http://www.facebook.com/kris.cadagan Kris Cadagan

    The Board of Supes have nothing to do with it. There is a citizens' initiative on the SF November ballot that, if passed by SF voters, would simply establish a study group to help SF find better ways to efficiently use water. And heaven knows that SF needs that because it is the only city or county of any size in the state that doesn't recycle a drop of water.

    • http://oaklandgeology.wordpress.com Andrew Alden

      Kris, the initiative states that the study group will furnish a plan that the Board of Supes must consider for the 2016 ballot. That plan is supposed to study all kinds of improvements to the water system, but it must also include dam removal. The city can certainly do a lot more recycling, but who would care about an initiative that only dealt with that? The restoration of Hetch Hetchy is either the carrot that will draw out the voters or the poison pill that will sink the initiative. Either way, it's a bold proposal that I think is here to stay.

    • Andrew Alden

      Kris, the initiative states that the study group will furnish a plan that the Board of Supes must consider for the 2016 ballot. That plan is supposed to study all kinds of improvements to the water system, but it must also include dam removal. The city can certainly do a lot more recycling, but who would care about an initiative that only dealt with that? The restoration of Hetch Hetchy is either the carrot that will draw out the voters or the poison pill that will sink the initiative. Either way, it's a bold proposal that I think is here to stay.

  • mbat66

    The restoration of the Hetch Hetchy Valley is a noble idea. It's a travesty that it was lost to modern man a century ago. The problem is how to come up with a new water supply for 2M+ people. It'll take decades for all the environmental studies to be done before the arguments can begin on a replacement.

    The Hetch Hetchy, with its crystal clear mountain spring water, provides the bay area with one of the purest water systems in the world. The SF civic leaders, at the turn of the 20th century, who fought for 20 years to get the dam built, had a great vision to provide the bay with a pristine water supply. The grandiose Hetch Hetchy Valley was lost to accommodate the need for clean H2O. It'll be another long, hard fought struggle to remove the dam.

    Even if the initiative passed, there would be several dozen lawsuits to prohibit the undamming for decades to come. You need viable alternatives in place just to get to the middle ground. Disrupting the current system could change not only the entire ecosystem of No Cal., but lead to disturbing and alarming shortfalls in water shed levels, if well funded studies aren't implented and foresight is not used to present sustainable alternatives to the current supply.

    The first order of business are a series of environmental studies done separately by distinctly different groups. As was the case 100 years ago, this fight could ultimately be settled by the Supreme Court. And quite frankly, that's probably what you could expect

  • ryan

    There are numerous pump stations in the valley (I have worked at a couple), so this is not an entirely gravity fed system as you stated above. Great balanced review, thanks.