Lower Russian River flows to be halved under state order to preserve stored supplies

The Sonoma County water agency received permission Monday to immediately cut stream flows in the lower Russian River by more than half in an effort to conserve water stored in Lake Sonoma.

Instream flows in the upper river, above Dry Creek, which is fed by releases from Lake Sonoma, already are being maintained at a very low threshold to keep as much water as possible in Lake Mendocino, the smaller of the two reservoirs.

The state decision means Sonoma Water, the county agency, and its contractors — the cities of Santa Rosa, Sonoma, Rohnert Park, Windsor, Petaluma and Cotati, and the Valley of the Moon, Marin Municipal and North Marin water districts — will have to use 20% less water from the Russian River, as well.

Both lakes Sonoma and Mendocino reservoirs are their lowest levels ever for this early in the year, with the warmest, driest months still ahead.

Most of the affected cities that get water from the lower Russian River already have asked for 20% reductions from customers.

Others on the upper river have had to cut deeper. Healdsburg last week ordered its residents to reduce their use by 40% compared to a year ago — double the mandatory 20% conservation level established in May that the city so far has been unable to meet.

Sonoma Water, which manages summertime releases from the reservoirs, is required to maintain minimum instream flows to protect habitat for protected salmon and steelhead trout. It can only lower those levels with permission from the State Water Resources Control Board.

The water agency had been restricting flows in the upper Russian River for most of the past year, with a minimum flow rate of 25 cubic feet per second, but now has permission to reduce the lower river flows from 85 cfs to 35 cfs, which will be noticeable to recreational users.

The water agency is hoping that reducing flows will allow it to maintain small reserves in the reservoirs in the event a third successive dry winter lies ahead.

The State Water Board also is expected to act Tuesday on emergency regulations that would allow it to suspend up to 2,400 water rights within the Russian River watershed, depending how severe the drought situation becomes. More than 900 water right holders, including grape growers, rural residents and municipal entities, already have been notified that there is too little water for them to exercise their claims to water this year.

You can reach Staff Writer Mary Callahan at 707-521-5249 or mary.callahan@pressdemocrat.com. On Twitter @MaryCallahanB.