The Sierra Club has filed suit against San Francisco's water department, accusing the agency of manipulating water-demand data to justify drawing more water than it actually needs from the Tuolumne River at Yosemite National Park. The lawsuit, filed in San Francisco Superior Court, calls on the San Francisco Public Utilities Commission to revise its state-mandated Urban Water Management Plan to reflect what the environmental group calls more modest, realistic water needs.
According to the San Francisco Chronicle, the Oakland-based Sierra Club argues that San Francisco officials are inflating population growth and future household water consumption figures, which the utility then uses to justify larger withdrawals from Hetch Hetchy Reservoir. The suit alleges the SFPUC disregarded its own financial department's more conservative demand estimates and instead advanced alternative projections suggesting substantially greater water use, according to the Chronicle's reporting. Higher demand projections translate into costlier infrastructure plans, and those capital costs can in turn drive rate increases for customers, the Chronicle reports.
A Long-Running Fight Over the Tuolumne
The dispute centers on how much water San Francisco holds back behind Hetch Hetchy Dam versus how much it releases downstream. The Sierra Club and other environmental groups accuse the city of storing too much water at the reservoir, a practice they say harms salmon runs and contributes to a drying foothill landscape along the Tuolumne corridor, per the Chronicle. The river currently averages just 21% of its natural flow during peak runoff season, a figure echoed by the U.S. Environmental Protection Agency. That shortfall matters because Phase I of the California State Water Resources Control Board's Bay-Delta Plan calls for 40% of unimpaired flow, with an adaptive range of 30% to 50%, to remain in the river from February through June to support declining salmon populations.
Mark Shahinian, speaking to the Chronicle, said the groups have battled the SFPUC since Hetch Hetchy was built and that San Francisco officials have not cared about their environmental impact for a hundred years. The Tuolumne River Trust has also pointed to the SFPUC's reliance on a hypothetical 8.5-year Design Drought model, a scenario the agency's own vulnerability assessment shows has a return period of once every 8,000 years.
The Numbers at the Center of the Lawsuit
The SFPUC's current Urban Water Management Plan estimates a 17% increase in San Francisco residents' water demand by 2050 and a 14% increase among wholesale customers by mid-century, projecting total system need at 222 gallons per day, the Chronicle reports. The Sierra Club asserts those SFPUC projections overestimate demand by roughly one-third. In a separate March 2026 report, the group said the utility has overestimated water demand by 45% to 50% on a 15-year planning horizon in every Urban Water Management Plan it has published since 2000, noting that even the 2020 plan overshot actual 2025 water use by 13% in 2025, five years after the plan.
The group also sent SFPUC commissioners a February 2026 letter about water-demand projections. The organization also points to conservation gains as evidence demand can stay flat: Bay Area residents and businesses served by the regional system cut per capita water use by 30% over the 25 years preceding 2026 through fixture upgrades, lawn removals, and conservation habits.
Ratepayers Already Feeling the Squeeze
The financial stakes extend well beyond San Francisco. The group's March 2026 analysis found the SFPUC projects retail water rates to climb more than 6.5% annually for seven years starting in 2027, an overall increase of at least 70% within eight years, with wholesale rate increases for suburban providers jumping from a planned 1% to more than 7% per year between 2025 and 2026. Hoodline previously reported that Palo Alto’s Utilities Advisory Commission backed a proposed 8% water-bill increase, subject to City Council approval, with a possible July effective date.
The Bay Area Water Supply and Conservation Agency, which represents 26 wholesale customer entities across San Mateo, Santa Clara, and Alameda counties, buys Hetch Hetchy water on behalf of 1.8 million suburban residents and businesses, according to BAWSCA. The SFPUC itself serves more than two dozen communities across those three counties, per the Chronicle, and defends its conservative water planning as essential to guaranteeing reliable supply for the region's people and economy through prolonged droughts and climate uncertainty.
What the Lawsuit Seeks
The lawsuit contends the alleged defects in the SFPUC's plan make it unfit under the Urban Water Management Planning Act, which requires large urban suppliers to submit updated long-term plans to the state Department of Water Resources every five years. The Sierra Club is asking the court to force revisions to the SFPUC plan, and the California Bay-Delta Plan update underway separately seeks to curb excessive withdrawals from the state's rivers more broadly. The Hetch Hetchy system itself dates to the 1913 Raker Act, which let San Francisco build dams and reservoirs inside Yosemite National Park; first deliveries reached the Bay Area in 1934, and the network now moves water across 160 miles of pipeline to roughly 2.7 million residents, according to BAWSCA's regional water system reporting.
The California Department of Water Resources oversees compliance with Urban Water Management Plans statewide. For now, the fight over whose numbers are right — the utility's growth forecasts or the environmental group's conservation-based projections — will play out in San Francisco Superior Court, with implications for both the Tuolumne's salmon runs and the water bills of millions of Bay Area customers.
