San Francisco’s Water Supply Planning
Steven R. Ritchie
Assistant General Manager, Water
October 28, 2025
SFPUC Overview: 24/7 Service in Perpetuity:
2 • As a critical public service, we have no end date to our operations. • Every day 2.7 million residents and thousands of businesses rely on the Hetch Hetchy Regional Water System for drinking water for public health, fire protection, and all aspects of their daily lives/businesses.
• 85% of the supply comes from the Tuolumne River, the remaining 15% is from local watersheds and reservoirs.
• Our daily operations emphasize high water quality and long-term water supply reliability. • Having junior water rights on the Tuolumne River means we have rights to very little water in dry years, but plenty of water in very wet years. As a result, we are very reliant on our stored water for reliability.
Wise Water Use and Regular Planning
3 • Active Conservation Programs:
• Both in San Francisco, and, through BAWSCA, regional efforts are always underway to promote conservation and the wise use of water.
• Among the Lowest Consumption Per Capita in the State
• San Francisco currently averages 41 gallons of residential per capita use, and Wholesale Customers average 55.1 gpcd (a 52% decrease since 1975-78 in residential per capita use).
• Urban Water Management Planning
• Every 5 years, all water agencies need to demonstrate that they have enough supply to accommodate anticipated growth over the ensuing 25 years.
4 • Smart Operations and Water Supply Planning:
• Our management decisions and planning are guided by “Water First”, Experience, and Risk Management.
• “Water First”: Water supply is top priority with hydropower generation a secondary consideration.
• Experience: There is plenty of water in normal years, but 1987-92 and recent droughts were very real and can be repeated or worse. Our fundamental planning premise is that there will be a worse drought in the future.
• Risk Management: How bad can conditions get, knowing that we cannot operate to zero storage at any point? Zero water in storage means no cushion for the next potential dry water year.
Smart Operations and Water Supply Planning
Hetch Hetchy Reservoir, January, 1991
5 6
O’Shaughnessy Dam Upstream Face – March 1991
All outlets except for
Canyon Tunnel are dry
SFPUC Water Supply Planning
Our Level of Service objective for water supply (adopted in 2008 as part of WSIP Programmatic EIR) is to manage a specific 8.5-year drought planning scenario (1987-92 followed by 1976-77) with no more than 20% rationing from a total system demand of 265 MGD.
Consequences of Being Wrong
“When considering all the factors
associated with the City’s
entitlements to water, its physical
system and the dire consequences
of just being wrong in the
forecasting of the length of
drought that may hit the City, I can
not agree with any comment that
the City’s operation rule is overly
conservative.”
Anson Moran, January 1994
8 Challenges Ahead
9 • 2018 Adopted Bay-Delta Plan:
• Unimpaired flow paradigm and existing agreements may require up to 93 million gallons per day (mgd) of impact to Regional Water System supplies. Healthy Rivers and Landscapes Program is an alternative currently being considered by the State. It contains greater instream flow contributions than current conditions but less than the adopted Bay-Delta Plan. • State Actions:
• Curtailments and proposed legislation have a potential impact on our water rights and supplies. • Population Growth:
• Population will continue to grow.
• Evolving requirements on State Housing General Plan Elements puts increased pressure on San Francisco and our Wholesale Customers to increase housing and their potential need for Regional Water System supplies.
• Climate Change
• Studies indicate shifts to more precipitation as rain than snow and more extreme events.
Alternative Water Supply Plan for the Regional Water
System
10 • This plan was requested by both the San Francisco Public Utilities Commission and the BAWSCA Board of Directors.
• This is not an adopted plan.
• It is not a plan to construct any particular project or projects. • It is a living planning document that gives decision-makers information regarding potential future water supply issues and potential actions to augment the Regional Water System supplies to retain our current, appropriate risk management approach.
Plan for Obligations, Build for Demands
11 • Regional Water System Existing and Potential Obligations:
• The Supply Assurance of 184 mgd for the Wholesale Customers • Supply allocation of 81 mgd for San Francisco
• San Jose and Santa Clara combined supply assurance of 9 mgd • Combined total of 274 mgd
• Total Regional Water System Demands
• 244 mgd based on 2020 Urban Water Management Plans
• We will be using one or more additional sets of demand projections for further analysis, in addition to the legally-required Urban Water Management Plan projections.
Alternative Water Supply Plan Recommendations
12 • Advance the planning of Purified Water Projects
• PureWater Peninsula
• South Bay Purified Water
• Further develop supplies from existing and other projects • Regional Groundwater Storage and Recovery Project
• Alameda Creek Recapture Project
• San Francisco Groundwater Project
• PureWaterSF
• Potential projects with Turlock and Modesto Irrigation Districts Questions?
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