Santa Rosa staff: Lake Pillsbury storage reduced after PG&E gate limits; recycled water production steady

City water staff told the Board of Public Utilities that operations upstream of the Russian River are changing after PG&E lost the ability to operate slide gates at Lake Pillsbury, a condition that reduces that reservoir’s effective storage and is prompting requests to the Federal Energy Regulatory Commission for temporary and potentially longer‑term variances.

Peter Martin, deputy director for water resources, said Lake Pillsbury was about 57,000 acre‑feet as of the presentation and that PG&E can no longer operate gate equipment that allowed storing an additional roughly 20,000 acre‑feet in spring and summer. Martin said that loss represents approximately 25% of the reservoir’s total storage and that PG&E filed for a variance from required minimum streamflows under its FERC license in February. That variance request would allow reductions of minimum flows in the project’s east branch of the Russian River from roughly 75 cubic feet per second (cfs) down to as low as 25 cfs, depending on hydrologic scenarios and temperature concerns for the Eel River.

Martin said Lake Mendocino and Lake Sonoma were currently holding more water; he reported Lake Sonoma at about 265,000 acre‑feet with an additional 19,000 acre‑feet stored under a minor deviation and said Lake Mendocino storage was increasing toward the forecast pool operations. He also told the board that Sonoma Water filed a temporary change petition on April 10 to apply its hydrologic index to Lake Mendocino rather than cumulative inflows from Lake Pillsbury and to align minimum instream flows with the 2008 biological opinion for salmonid protection under the Endangered Species Act.

Andrew Romero, reclamation superintendent, briefed the board on recycled water. He said the plant had produced more than the historical average during the current water year but that flows were decreasing with warmer weather and that the plant was producing around 20,000,000 gallons per day. Romero said recycled water storage was just above 1.1 billion gallons and staff expected to be closer to 1.2 billion gallons by May 1. With current storage and plant flows, Romero said staff expected to meet all contractual obligations and were preparing for the urban and agricultural irrigation season.

Martin also highlighted local groundwater outreach and monitoring programs the groundwater sustainability agencies are implementing. He described the Flow Smart program — a free voluntary groundwater flow monitoring meter program for well owners funded by grants — a multi‑year voluntary well monitoring program (referred to in the presentation as the “lehi up program”) that obtains spring and fall measurements and coordinates with agricultural groups, and a new Well Aware grant program offering tools and resources to help well owners use groundwater more efficiently. Martin noted that data from these programs remains aggregated and anonymous to address well‑owner concerns and that public outreach materials and infographics are available at SantaRosaPlainGroundwater.org.

Board Member Mullen commented that losing a quarter of Pillsbury’s storage was significant for downstream supply reliability and asked whether this is the new normal as facilities are decommissioned and reconfigured. Martin answered that PG&E discovered the storage limitation in 2022 and has been operating under a one‑year variance while pursuing longer‑term measures with FERC; he noted discussions with the Russian River Flood Protection and Watershed groups and that the Russian River area authorities are evaluating pumped diversion options and other long‑term strategies if the Pillsbury storage remains constrained.

There were no formal board actions tied to this briefing. The presentation served as an informational update on regional storage dynamics, state and federal filings affecting minimum flows, recycled water production and storage, and new local groundwater monitoring and outreach programs.