Santa Rosa briefs board on water supply, reservoirs, groundwater sustainability and recycled water operations

Deputy Director Peter Martin and other Santa Rosa Water staff gave a comprehensive water supply update covering reservoir operations, state petitions, a new biological opinion, the Santa Rosa Plain Groundwater Sustainability Agency (GSA) annual report, and recycled water operations.

Martin said Sonoma Water filed a temporary urgency change petition with the State Water Resources Control Board seeking to base in‑stream flow requirements on Lake Mendocino storage rather than cumulative inflow to Lake Pillsbury. "The request at this time is that they are able to, set their in stream flow requirements under their water rights to be based on the storage in Lake Mendocino," Martin said. He said the requested change is under state review and that the petition process can affect timing of flows and operations; staff noted these temporary change petitions are typically filed twice a year and last 180 days.

Martin and staff reviewed current reservoir storages: Lake Pillsbury storage around 50,000 acre‑feet, Lake Mendocino about 100,000 acre‑feet, and Lake Sonoma at roughly 258,000 acre‑feet during the reporting period. He noted operational variability related to PG&E’s Potter Valley Project operations and a pending variance request by PG&E. Martin highlighted that reservoir operations informed by forecast‑informed reservoir operations helped Sonoma Water capture additional yield this water year.

Staff announced the National Marine Fisheries Service issued a new biological opinion allowing conjunctive operation of two reservoirs with a 10‑year permit and associated reasonable and prudent alternatives for endangered fish species protections. Martin said the opinion includes measures that build on earlier restoration work in the watershed.

On groundwater, Martin summarized the Santa Rosa Plain GSA 2024 annual report (water year Oct. 1, 2023–Sep. 30, 2024). He noted the basin’s mandated sustainability indicators and said while drought years previously showed some groundwater level declines, the recent wet year largely reversed declines and storage conditions improved. The GSA continues pilot projects including aquifer storage/recovery and stormwater recharge and has added monitoring wells in data‑gap areas.

For recycled water, staff said irrigation season has begun, storage ponds hold about 1.18 billion gallons, and delivery allocations for agricultural users are unchanged from last year (about 1.4 billion gallons allocated). The team plans a mid‑ to late‑July annual maintenance shutdown for the Geysers system.

Board members asked clarifying questions about FERC variance timing, the effect on supplies if pipeline constraints or delivery outages occur, and potential collaboration on recycled water projects and storage. Martin and other staff said the city will continue to monitor Sonoma Water actions, pursue opportunities for recycled‑water storage and transmission collaboration, and track GSA implementation funded by grants.

No formal board vote was taken; staff closed the briefing and said they will continue to report on developments.