Sonoma Water Takes Action to Save Water in Lake Mendocino

For Immediate Release - January 8, 2021

Contact: Brad Sherwood,, 707-322-8192

(Santa Rosa, CA) The Sonoma County Water Agency (Sonoma Water) yesterday requested a Temporary Urgency Change Petition (TUCP) from the State Water Resources Control Board (State Water Board) to help preserve water supply in Lake Mendocino due to very low storage levels for this time of year. The TUCP was submitted due to drought conditions, severely low storage levels in Lake Mendocino, and a hydrologic index for establishing minimum flows not aligning with the watershed conditions. On January 1, 2021, the water supply condition for the Russian River was reclassified as Normal from Dry based on the cumulative inflow into Lake Pillsbury for the water year to date. This designation of Normal water supply conditions does not accurately reflect the conditions and lack of rainfall experienced in 2020 in the Upper Russian River.  As measured at Ukiah, recorded rainfall for 2020 was 11.32 inches, which amounts to 31% of the average rainfall (37.01 inches) and the second lowest recorded rainfall since 1893. The TUCP and more water supply update information may be viewed at

“Filing a Temporary Urgency Change Petition is one tool to saving water in Lake Mendocino due to potential drought conditions,” said Sonoma Water General Manager Grant Davis. “Our community can help too by saving water by using water wisely. While there is still opportunity for rain in the upcoming months, we must prepare now for continued dry conditions and implement every tool we can to save water in our reservoirs. Another tool Sonoma Water has implemented is the use of Forecast Informed Reservoir Operations, or FIRO, which increased Lake Mendocino’s water storage by 19 percent or 12,000 acre-feet last spring. Without FIRO tools being used to manage flood control operations last year under a major planned deviation to the flood control manual, Lake Mendocino would be in a much worse situation right now.”

The Sonoma-Marin Saving Water Partnership is implementing a rare Winter-time public outreach campaign seeking the community’s help in saving water. The Partnership represents Sonoma Water and its wholesale water contractors, or the cities that deliver drinking water to more than 600,000 residents in the North Bay. Learn more about the Partnership at

Current Water Supply Conditions as of 1/8/21:

Lake Mendocino:  42% of water supply capacity

Lake Sonoma:  65% of water supply pool

Last Water Year (2020) was the third driest of 127 years of record in Ukiah. 

As of January 1, Sonoma Water must make releases from Lake Mendocino to manage minimum instream flow requirements in accordance with Normal water supply conditions – which means Russian River in-stream flow requirements have increased and thus releases out of Lake Mendocino must be increased to meet these requirements. The in-stream requirements are mandated as part of Sonoma Water’s water rights permits and State Water Board Decision 1610.

With no significant rain, Lake Mendocino water supply levels are decreasing, and Sonoma Water is discussing with the State and local stakeholders how to continue water saving efforts at Lake Mendocino. The TUCP would temporarily change Sonoma Water’s water rights to determine the water supply condition for the Upper Russian River and associated minimum instream flow requirement on storage thresholds in Lake Mendocino, and not reliant on Lake Pillsbury cumulative inflow. This management tool would provide more accurate determination of the water supply condition in the Russian River and the associated minimum instream flow requirement. In 2013, Sonoma Water used this same water management tool to successfully save water in Lake Mendocino. In late 2013, Sonoma Water filed a Temporary Urgency Change Petition with the State Water Board requesting similar changes. The State Water Board approved the Petition and the requested changes successfully managed water supply storage at Lake Mendocino during the serious drought conditions that continued through 2014. 

At this time, no changes are being requested for how minimum instream flow requirements are determined for Dry Creek and the Lower Russian River. Although Lake Sonoma storage levels are below normal for this time of year, that reservoir has adequate water supply to meet minimum instream flows in Dry Creek and the Lower Russian River based on the State Board’s Decision 1610. However, Sonoma Water will re-evaluate supply conditions in Lake Sonoma in the spring to determine whether it is necessary to file a subsequent Temporary Urgency Change Petition to address a significant depletion at Lake Sonoma storage.


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