SANTA ROSA, CA – The State Water Resources Control Board issued an order at the end of June to approve temporary urgency change petitions filed by Sonoma Water. The petitions requested that the water supply condition in the Russian River, which sets the minimum instream flow requirements in the Upper and Lower Russian River, be determined based on storage thresholds in Lake Mendocino rather than cumulative inflow into Lake Pillsbury in the Eel River watershed.

The petitions also requested the minimum instream flow requirement on the Upper Russian River be reduced from 185 cubic feet per second (cfs) to 125 cfs and on the Lower Russian River from 125 cfs to 70 cfs as required by the 2025 Russian River Biological Opinion. The temporary order is in effect for 180 days and reflects reduced water diversions from the Eel River and the need to set minimum instream flow requirements based on watershed and reservoir conditions in the Russian River watershed.

The approved changes include a revised hydrologic index that relies on storage levels in Lake Mendocino rather than inflow to Lake Pillsbury. The temporary order also lowers minimum instream flow requirements in the upper and lower Russian River under Normal water supply conditions to improve the quantity and quality of habitat for endangered fish species.

The petition aligns Sonoma Water’s operations with the new 2025 Biological Opinion issued by the National Marine Fisheries Service. The updated guidelines recommend lower flows during the dry season to improve conditions for salmon and steelhead, and to preserve cold water storage in Lake Mendocino for use later in the year.

Without these temporary changes, current minimum flow requirements could force releases from Lake Mendocino that deplete storage, jeopardizing both drinking water supplies and fish habitat during future dry months.

The temporary changes will also support the long-term effort to update the state-issued Decision 1610, which currently governs streamflow and water year classifications in the watershed. Sonoma Water is preparing an environmental impact report to support permanent modifications to the decision.

For more information about water management in the Russian River watershed, visit: www.sonomawater.org/tucp