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Sonoma Water files petition to maximize reservoir storage

The Sonoma County Water Agency has filed a petition with the State Water Resources Control Board to ensure that already depleted reservoirs are not further affected by reduced flows from the Potter Valley Project due to a mechanical failure at the PG&E hydroelectric facility.

The Potter Valley Project diverts water from the Eel River through a tunnel and hydropower facility operated by PG&E. The water flows through the Potter Valley and into Lake Mendocino. Typically, the amount of water allowed to flow into the Russian River is determined by inflow into Lake Pillsbury, located upstream of the Potter Valley Project. But because the water imported from the Eel River into the Russian River will be greatly diminished due to the hydropower plant failure, that calculation won’t be accurate.

Sonoma Water has filed a Temporary Urgency Change Petition (TUCP) requesting that minimum water flow into the Russian River be determined based on storage thresholds at Lake Mendocino. Lake Mendocino and Lake Sonoma remain at or near their lowest levels for this time of year since filling in 1959 and 1986. This makes it even more critical that minimum flow into the Russian River be determined by a hydrologic index representative of the Russian River watershed.

“This is a common-sense approach to a complex situation, which is exacerbated by the ongoing drought,” said Sonoma County Supervisor and Sonoma Water Board of Directors Chair Lynda Hopkins. “We need to do everything we can to maintain water in our reservoirs for the health and safety of our communities and environment. I’m hopeful the State Water Board will support our efforts to conserve every drop of water and get through this drought together.”

If the TUCP is approved, the water supply condition would remain “critical” through the December 31, 2021. On January 1, 2022 the water supply condition will be re-evaluated based on storage in Lake Mendocino and monthly thereafter until June 1, 2022 when the water supply condition will be set until the end of the year.

PG&E officials have indicated that it is unlikely the company will repair the facility given the likelihood that it may surrender its license to continue operating the PVP.

A copy of the November 2021 TUCP is available at: https://www.sonomawater.org/tucp

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