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Balancing water supply resilience and ecology

As policymakers consider updates to the Bay-Delta Plan, a Stanford analysis outlines challenges and strategies to support future water security in the San Francisco Bay Area in the face of climate change.

Water is released from the Hetch-Hetchy reservoir
Hetch Hetchy Reservoir, which feeds into the Tuolumne River, provides one of the main sources of drinking water for the San Francisco Bay Area. Image credit: Sundry Photography / iStock

California’s challenge to balance water supply sustainability and ecosystem health comes to a head in the San Francisco Bay Area. A recent Stanford University study delves into the complexities of the issue, shedding light on the challenges, and offering innovative solutions.

The paper focuses on the Bay-Delta Plan, a critical water management strategy drafted in 1996. Declining fish populations and the specter of drought exacerbated by climate change, among other changes, have led to calls to update the plan. Central to the debate is the requirement for unimpaired flow in the Tuolumne River, a vital source for the San Francisco Public Utilities Commission (SFPUC), which serves millions of people. The SFPUC and Central Valley irrigation districts have proposed a voluntary agreement plan that emphasizes interventions such as habitat improvements and predation management, instead of large cutbacks in water withdrawals.

The Stanford analysis highlights the nuanced impact of the amended Bay-Delta Plan on Bay Area water supply reliability. Its findings underscore the need for a dynamic approach, considering uncertainties and changes over time. Among its key revelations is how the proposed amended plan could lead to faster depletion and slower recovery of water storage during droughts. This would make earlier conservation responses and careful management of storage reserves crucial.

This highlights the need to integrate coping strategies to understand the opportunities available to mitigate the impact of the amended Bay-Delta plan.

Richard Luthy Professor of Civil and Environmental Engineering

The study also recognizes the importance of proactive measures in non-drought years, emphasizing the value of effective management in navigating dry spells. The researchers suggest policymakers adopt tailored strategies that acknowledge unique risks, such as setting quantitative targets for ecosystem health alongside sustainable water supply standards.

Luthy is the Silas H. Palmer Professor of Civil and Environmental Engineering, a professor, by courtesy, of Oceans at the Stanford Doerr School of Sustainability, and an affiliate at the Stanford Woods Institute for the Environment. Additional co-authors include Scott Fendorf, the Terry Huffington Professor of Earth System Science and a senior fellow at the Woods Institute; Bridget Gile, a PhD candidate in civil and environmental engineering; Randall Holmes, a lecturer in the Civic, Liberal, and Global Education (COLLEGE) program at Stanford University; and Allison Sherris, a postdoctoral fellow at the University of Washington. Holmes and Sherris were PhD students at Stanford University during this work.

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