Mar 11, 2025 City Council Meeting Item 13.C Review Sonoma Water Transmission System Budget Subject: Clarification on Sonoma Water Budget
Dear Mayor Ford, Vice Mayor Lemus, and Councilmembers Sparks, Harvey, and Savage, Thank you for the report on a forward-looking budget for Cotati's potable water supply. I’ve attended a number of WAC/TAC meetings, and I’m very impressed with the overall process as well as the effort to encourage water savings across the region.
However, for the Eel River/Potter Valley bypass MOU, the Sonoma County discussions seems to have been behind closed doors. Humboldt County is the only place there has been open discussion. This can be viewed Feb 11 Start at 1hr52min – starting with a description of the MOU https://humboldt.granicus.com/player/clip/2052?view_id=5&redirect=true And Documents including MOU at
https://humboldt.legistar.com/LegislationDetail.aspx?ID=7133222&GUID=188CA1D2-A9C9-47D6-AE63- EF8A786CCB3C&Options=&Search= .
From the Sonoma Water report most of the costs are for the water transmission, pipelines and the BO of Dry Creek. For the “Proposed Rates for FY 25-26” PdfPktPg226 which line-item Charge does the cost of managing Lake Sonomo and Lake Mendocino during their water supply phase fit? Understanding the geographical relationship between Lake Sonoma and Lake Mendocino is crucial for assessing our water supply's resilience. Lake Sonoma (245,000 acre-feet) and Lake Mendocino (122,500 acre-feet) are the primary storage reservoirs. Water from these lakes flows through natural river channels to the Wohler Collectors. Lake Sonoma's water travel is relatively short (I measure 22 road miles) via Dry Creek and the lower Russian River, while Lake Mendocino's water travels significantly longer distance (I measure 60 road miles) via the upper Russian River.
Sonoma Water's water extraction/reporting and delivery figures pertain to areas south of Dry Creek joining the Russian at Healdsburg, not the upper Russian River.
Based on Sonoma Water's 2020 Urban Water Management Plan (June 2021), and doing a simplistic analysis,
a) Lake Sonoma appears to offer a multi-year water supply for Sonoma Water contractors. b) Lake Mendocino primarily serves the upper Russian river, which is approximately 40,000 residents (compiled from standard sources) in the unincorporated areas, a lot of it I would assume ag. Future drought resilience efforts, such as upper Eel River Spring transfers, would likely primarily benefit this group. The proposed Alexander Valley Water District formation further emphasizes this point.
For major cities in the Upper Russian, Ukiah, with a population of 16,072, relies on the substantial Ukiah Groundwater Basin as its primary water source. Their 2020 water usage was 3,030 acre-feet, with a projected 2040 demand of 21,184 acre-feet a 7 times increase for slight increase in population.
Cloverdale (population 8,964) has significant water rights from Russian River wells (27,92 acre-feet/year) and Sulphur Creek (73,653 acre-feet).
It seems to me that Cotati and other Sonoma Water contractors have a robust, multi-year water supply from Lake Sonoma. Lake Mendocino and its associated water rights are primarily beneficial to the upper Russian River users.
Since Sonoma Water reports to the Sonoma County Supervisors, it's important to acknowledge that the cost of managing the upper Russian River should not solely fall on Sonoma Water Contractors ratepayers.
To provide historical context for the evolution of water supply I found:
1907: The commercial hydroelectric Eel River Potter Valley Bypass system begins, with the added benefit of providing "waste water" to the East Fork of the Russian River. 1959: Lake Mendocino filled, providing water supply resilience for future Sonoma Water contractors.
During the 1970s droughts, I have heard the Eel River hydroelectric system transferred all the upper Eel River flows to the Russian River.
1982: Lake Sonoma filled, providing urban water for Sonoma Water's growing customer base.
Source: https://mendoiwpc.com/our-shared-water/history/ Thank you for considering these points.
Neil Hancock, Cotati