Restoring Hetch Hetchy Valley

Jay Lund, the Ray B. Krone Professor of Environmental Engineering, University of California – Davis

In November, the people of San Francisco will vote on looking into alternatives to capturing water at the Hetch Hetchy reservoir site, which could lead to restoring the fabled valley in Yosemite National Park.  While this modest step faces steep opposition, the vote is an important event in the evolution in the city’s and state’s thinking about how to provide high quality water for people.

Hetch Hetchy Valley in the early 1900s, before construction of the O’Shaughnessy Dam. Wampa Falls is on the left.

In the early 1900s, when the Hetch Hetchy project was initially being conceived, death rates from water-borne diseases were substantial, water treatment was in its infancy, and cities were growing rapidly.  Building high elevation reservoirs in the mountains far from human activity offered abundant supplies of high-quality water, supporting tremendous economic and population growth with additional benefits from hydropower. Many large cities pursued this strategy from the late 1800s into the early 1900s, including New York, Los Angeles, Seattle, Portland, San Francisco, and Oakland (EBMUD).  At that time, these systems were wonders of engineering technology and public service.

In the case of San Francisco, the Hetch Hetchy water system, with four upstream dams including O’Shaughnessy dam on Hetch Hetchy Valley, began deliveries in 1934 and today provides water to 2.4 million people (mostly outside of San Francisco).  This system was so well engineered that it was largely neglected for decades, until deterioration and earthquake risks resulted in the need for a $4.6 billion for retrofit and rebuilding.

Hetch Hetchy Reservoir in Yosemite National Park. Photo by Samuel Wong, April 2006.

Today, other ways could be found to provide water supplies to these cities, mostly by treating water downstream of pristine mountain watersheds.  But water systems last much longer than the technologies, economies, and social norms which prevailed when they were built.  Auguring modern environmentalism, opposition to Hetch Hetchy was a major environmental cause in the early 1900s, famously involving the early Sierra Club and John Muir.  Even at that time, competing approaches to urban water supply were becoming accepted, with Sacramento opting to treat local water rather than damming a Sierra river.

In recent years, the possibility of restoring Hetch Hetchy Valley has been revived several times.  These efforts are motivated to avenge the environmental loss of the 1920s, restore the Valley to function as a park, goad the Bay Area about practicing their environmental ethics, and illustrate the potential for renewing California’s environment while supporting a growing economy.  Although rhetoric on the subject is enormous, some important engineering, economic, and environmental insights have been established.

First, regardless of Hetch Hetchy reservoir’s fate, the Tuolumne River water will remain the water major source for San Francisco and much of the Bay Area.  Given existing infrastructure, hydrology (even with climate change), water quality, and water rights, Tuolumne River water will and should remain the most reliable, economical, and high quality source of water for the Bay Area.

Second, the Bay Area does not need Hetch Hetchy reservoir to continue delivery of high-quality water from the Tuolumne River.  Several independent and peer-reviewed studies have shown that modifying the Hetch Hetchy aqueduct to take water from Cherry Reservoir or the much larger Don Pedro Reservoir downstream (built in 1971) would allow the Bay Area to receive full deliveries of its current supplies in almost all years, with only small shortages in remaining years.  Remaining shortages could be supplied from various state, federal, and local sources, including water purchases from agricultural areas, groundwater, and Bay Area water conservation.

Third, there is growing interest in agricultural communities, including the Modesto area, to sell water to the Bay Area as a way of improving their own financial conditions.  In a lesson on California water rhetoric, some agencies which denied any interest in selling water to the Bay Area a decade ago, now advocate limited water sales.

Fourth, eliminating the Hetch Hetchy reservoir would be costly, from one to ten billion dollars.  Much of the cost would be for expanding water filtration for Hetch Hetchy Aqueduct water, something likely to be needed eventually anyway.  Lost hydropower would be significant, but much less expensive.

Fifth, restoring Hetch Hetchy Valley poses some environmental dilemmas.  Removal of the dam will not help the distressed Central Valley native aquatic ecosystem, as the larger Don Pedro reservoir would remain downstream.  It is likely that additional Tuolumne River water will be required for helping to restore the Delta, further straining the city’s water supplies.  Also, the restored Valley would become a major tourist destination, implying the Valley could be commercialized and crowded – more like Yosemite Valley than the wild cathedral envisioned by John Muir.  Hetch Hetchy Valley today is comparatively little visited and uncrowded.

Finally, long-term trends in California most likely favor eventual restoration of Hetch Hetchy Valley.  In the 1920s, California had a population of 3 million, and Yosemite Valley was uncrowded and largely unknown.  Today, California has almost 40 million people and Yosemite Valley is overcrowded with tourists from California and around the world.  Each decade, modifying Bay Area water supplies becomes less expensive relative to physical restrictions on California’s recreational economy and growing scarcity of beautiful Sierra valleys.  The economics of restoring Hetch Hetchy Valley should become more favorable with time, even if they are unfavorable today.

With time, California must change to remain prosperous and environmentally desirable.  Environmental and economic sustainability both require change and adaptation, not stagnation.  Restoration must be forward-looking.  Hetch Hetchy is an example of how California must expect and explore changes in water management, and how making changes will remain controversial, as it always has been.

About jaylund

Professor of Civil and Environmental Engineering Director, Center for Watershed Sciences University of California - Davis
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