SFPUC details regional water-supply planning, defends 8.5-year design drought

San Francisco — At a San Francisco Public Utilities Commission meeting, Assistant General Manager for Water Steve Ritchie outlined the agency’s multi-decade water-supply planning framework and defended the use of an 8.5-year design drought as a conservative modeling tool.

Ritchie told commissioners that about 85% of San Francisco’s supply comes from the Tuolumne River and that the city relies on stored water because its Tuolumne rights are junior in dry years. He said the utility’s long-term planning emphasizes ‘‘Water First’’ — prioritizing supply for drinking water and public health over hydropower — and uses an 8.5‑year drought sequence derived from the 1987–1992 drought as a stress test in environmental review and project modeling. "The consequences are too great for being wrong," Ritchie said, noting the system must avoid operating at zero storage.

Ritchie reviewed alternative-supply options under study, including purified-water projects (Pure Water Peninsula, South Bay Purified Water, Pure Water SF), the Regional Groundwater Storage and Recovery project, and the Alameda Creek Recapture Project. He said the regional planning exercise is a ‘‘living planning document’’ intended to give decision makers options rather than obligate construction of any single project.

Commissioners pressed staff on the policy’s implications for rates and capital spending. Commissioner Stacy asked whether the urban water management-plan projection of 2.44 million gallons per day (MGD) by 2045 alters operational decisions; Ritchie said those projections are a 25-year legal planning requirement and are used as an outer envelope for stress testing, but that capital and budget choices ultimately determine what projects are built. He noted that new supplies are increasingly expensive and that the commission will weigh trade-offs in the upcoming budget process.

Public commenters, including Tom Smigel of the Bay Area wholesale agencies (BOSCA/BASCA), generally supported planning for obligations but urged that execution match demonstrable demand. Several callers and commenters said the 8.5‑year design drought pushes a planning mindset of perpetual drought, risks unnecessary capital spending and could increase rates for retail customers. A caller from Redwood City argued the 8.5‑year sequence is extremely unlikely and urged the commission to pick a ‘‘scientifically intelligent’’ number to avoid imposing excessive costs on retail purchasers.

Ritchie emphasized ongoing modeling and annual analysis to detect trends in snowpack and precipitation patterns, and he said staff are preparing updated demand projections and an urban water management plan in the coming cycle. The commission did not vote on policy changes at the meeting; commissioners asked staff to continue refining planning materials and to incorporate public feedback during the rate- and budget-setting processes.

The SFPUC’s next steps include continued modeling, updates to the urban water management plan, and future presentations on alternative-supply options and budget trade-offs.