Please attach this to Cotati City Council item May 27 for Public Hearing for Water and Sewer Rates Cotati's urban water supply is partly sourced from the Sonoma Water Transmission System, which draws water from the lower Russian River at Wohler Collector.
While the current rate increases appear reasonable, it has also been identified that deferred capital improvements in the Sonoma Water Transmission System will need to be addressed in the future.
There has been discussion on the new Eel Russian Project authority and funding sources. I would like to pose the question: Does it offer any urban water resiliency for ratepayers whose water source is the lower Russian River? Based on recent Marin Water presentations, Sonoma Water Contractors have large winter flows that can meet water withdrawals as well as Lake Sonoma storage. These flows fit well within Sonoma Water agency’s water rights and Russian River flows.
On April 23, 2024, Cotati (Item 10.B) joined a Marin Water initiative to fund legal research and analysis regarding the impact of the Potter Valley Project diversion, for a cost to all participants of $100,000.
At its April 15, 2025, meeting (starting @21minute mark), the Marin Water Board authorized the “Winter Water Conveyance Project”. This project is a new 36-inch pipe from the North Marin Aqueduct to Nicasio Reservoir for long-term water resiliency.
The Marin Water presentation indicated that the Russian River has the capacity to be tapped for between 3,800 and 8,100 acre-feet (AF) annually for this project. The presentation included a Winter Availability Table showing that for the drought year 2021 there was an 80,000+ AF "excess” of winter flows (natural flows) over required instream flows (Chart attached). A Marin Water brochure called “Winter Water Conveyance Project” states “Reliability. This project relies upon water being available for purchase during dry years. However, even in dry years, the Russian River watershed generates substantial flows.”
Public sources indicate:
a) The Sonoma County Water Agency (SCWA) states on its water supply page that Lake Sonoma provides the majority of water for its urban water service area i.e., 600,000+ people in Sonoma and Marin. (Lake Sonoma has a capacity of 250,000 AF and was completed in 1983) b) SCWA's Urban Water Management Plan identifies its water rights as up to 75,000 AF annually, and in 2024, 44,530 AF were drawn from the Wohler Collector in the lower Russian River.
Sonoma Water has obliquely discussed the contributions of water from the upper Russian River and the need for a new Eel to Russian River transfer. Notably, in a requested support letter (Cotati Council Agenda Item 11.A Oct 24, 2023) Sonoma Water asked contractors for a letter about the PG&E planned decommissioning of its Potter Valley Hydroelectric Project, that stated “halting diversions” (from the Eel River) “would make the drinking water supply for 600,000 additional people less reliable”. This claim has been repeated by different official parties in Mendocino and, notably, Lake County BOS – yet the Marin Water Board presentation shows no such dependency.
Sincerely Neil Hancock, Cotati. May 19, 2025 see attached Winter Availability Table from Marin Water Board presentation.