Despite being in the third year of a severe drought, California, the leading state for dam removals, continues to propose many dam removal projects. As recently as November 2012, Proposition F, designed to allocated funds towards an assessment of draining the Hetch Hetchy Reservoir by removing the O’Shaughnessy dam, was put to the ballot in San Francisco. Activists who consider Hetch Hetchy to be a crown jewel of Yosemite National Park, possibly more spectacular than Yosemite Valley, have been pushing to restore it to its former state for years. However, when San Francisco residents were asked to weigh in on the proposal through the ballot, the proposition was soundly defeated. While in many instances dam removal can be, both economically and environmentally, the best course of action, in this case the residents of San Francisco have got it right. Dismantling the fully functioning O’Shaughnessy Dam, which provides approximately 85% of San Francisco’s water, is, at the very best, shortsighted.
In California, dams are used for hydropower, water supply management and flood control. Concerned parties, however, often cite dams as a blockage to fish migration, which can impede anadromous fish spawning. This is a major concern because several endangered and threatened fish species in California are anadromous and need to be able to migrate to the ocean in order to live out their full life cycle. However, respected University of California Davis biologist, Dr. Peter Moyle assures that, historically, few native fish species inhabited the Hetch Hetchy Valley and thus, native fish endangerment is not truly a major concern with the O’Shaughnessy Dam. Unlike the O’Shaughnessy, most dams removed in California to date have been small and inconsequential, making them relatively easy and inexpensive to take down. Age and need for significant, costly repairs are among the main reasons given for dam removal and it is usually quite clear that the ecological benefits of removing such dams outweigh the economic benefits of leaving them intact. This is not the case with large functioning dams, such as the O’Shaughnessy. Among the most important factors to consider about major dam removal projects are the expenses, the significant loss of hydropower (hydropower accounts for approximately 15% of California’s electrical grid), and, of course, the decrease in water supply and quality.
Many dams like the O’Shaughnessy are being considered for removal purely for ecological gains, as mentioned above. However, there are many uncertainties, specifically with the removal of the O’Shaughnessy, which must also be considered before a decision can be made regarding the fate of Hetch Hetchy Reservoir. For instance, is there really a way to remove this massive dam in a cost-effective manner? How would the removal impact the environment, both upstream and downstream? And finally, is it even possible to fully restore a valley that has been underwater for close to 100 years? In addition, a new water system to replace the reservoir, a high quality water source, would have to be constructed; a project that would be time, cost, and labor intensive. One must note that several scientific studies have shown that modifications to the Hetch Hetchy’s water delivery system could allow the Bay Area to receive sufficient water from other reservoirs along the Tuolumne River. However, the construction of such conveyances would be expensive.
The toll of the drought is visible along the shores of the Hetch Hetchy resevoir. March 11, 2014.