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May 16, 2006 > Hetch Hetchy

Hetch Hetchy

This is the third part of a series of articles exploring the origin and present state of the Hetch Hetchy water and power system that runs through the Tri-City area. San Francisco Public Utilities has begun a $3.6 billion capital improvement program to repair and modernize its water supply system. A debate has surfaced over the need for continued use of the O'Shaughnessy Dam that resulted in the flooding of the Hetch Hetchy Valley in Yosemite National Park.

The Proposal:

The massive overhaul of the San Francisco Public Utilities Commission (SFPUC) Hetch Hetchy water supply offers an opportunity to modify components of the system. Proponents of restoring Yosemite's Hetch Hetchy Valley have lobbied for changes claiming that a practical alternative would continue a safe and secure water and power supply for customers of the existing system. Environmental Defense, an organization dedicated to protecting environmental rights, has issued a study of the possibilities beginning with the caveat, "advocates bear the burden of proving that alternatives can be made to work." In the interests of promoting a healthy dialogue, it is noted that "the legitimate concerns of all stakeholders must be addressed."

Currently, the floor of Hetch Hetchy Valley lies 300 feet below the surface of O'Shaughnessy Dam waters.  Supplied by the Tuolumne River, Hetch Hetchy Reservoir holds 360,000 acre-feet of water, "slightly less than 25% of SFPUC's total storage capacity" and "approximately 85% of the SFPUC's supply." Irrigation Districts of Turlock and Modesto share water storage with SFPUC at Don Pedro reservoir, downriver from Hetch Hetchy. Don Pedro has approximately six times the capacity of Hetch Hetchy, but the irrigation districts hold "senior rights" to Tuolumne River flow. This means that in wet years, there is plenty of water for all, but in dry years, SFPUC relies on Hetch Hetchy for stability.

The actual transfer of water is a bit different than simply tapping Don Pedro for SFPUC requirements. Water storage at Don Pedro is used as a "water bank" that repays Modesto and Turlock for water diverted at Hetch Hetchy. In order to tap Don Pedro reservoir waters, a connection would be necessary between those waters and SFPUC San Joaquin pipelines. This would allow diversion of water from the Tuolumne River in winter and spring while summer and fall requirements would be handled by system reservoirs outside Hetch Hetchy. It is noted that in extremely dry years, additional supplies are necessary from an expanded Calaveras Reservoir and "a small reserve of additional supplies," would be possible elements of the Capital Improvement Program.

Power generation from Hetch Hetchy is an important and inexpensive energy source for San Francisco and the irrigation districts of Modesto and Turlock. The report estimates that "Tuolumne River hydroelectric plants would still provide enough energy to meet current municipal needs on an annual basis in all but the driest years." It cites more efficient power from new gas-fired plants that, "using less than 20% of the annual output of just one of them [500 MW power plant] could replace all of the foregone energy.

Costs of additional modification of the existing SFPUC Hetch Hetchy system are an issue for discussion as well as existing legal challenges from current users and amendments to the Raker Act that allowed flooding of Hetch Hetchy in the first place.

Is it worth the price? That question is debatable but certainly important enough for intelligent discussion and consideration. Restoration of Hetch Hetchy has been a topic of debate for years, ever since the area was set aside in 1864 by President Lincoln for "public use, resort and recreation...inalienable for all time." Now is a propitious time for national debate beginning with Bay Area residents, those who would be most directly impacted. With careful measure and balance of the benefits and costs, we may find a road toward managing our natural resources and protecting natural assets as well.

 An editorial of the Sacramento Bee dated September 29, 2004 concludes, "Nobody is asking the Bay Area to give up any water. Nothing horrible is about to happen. Something magnificent might happen that would restore a valley in a national park. A serious conversation is appropriate for the future of a national public asset."

Source: Paradise Regained, Solutions for Restoring Yosemite's Hetch Hetchy Valley, Environmental Defense, 2004. Complete report available at or call (510) 658-8008.

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