Reservoirs in fair condition, efficient water use encouraged’
By Sonoma County Water Agency
Russian River water supply conditions changed to “critical” today under the Sonoma County Water Agency’s water rights permits and State Water Resource Control Board’s Decision 1610. Under Decision 1610, issued in 1986, a water year is declared normal, dry, or critical on the first of each month between January and June based on cumulative inflow into Lake Pillsbury, located in Lake County on the Eel River.
This “critical” designation means the water agency is permitted to reduce Russian River flows to preserve water storage in Lake Mendocino so there is enough for all water users and for release in the fall to support migrating Russian River Chinook salmon, listed as threatened on the Federal Endangered Species List.
“I can’t remember the last time that a water year was designated as critical, but we’re in much better shape than we were during the drought of the 1970s,” said Assistant General Manager of Operations Pam Jeane. “First, we built Lake Sonoma, which opened in 1983 and nearly quadrupled water storage. Second, water conservation is part of the Sonoma County lifestyle. In the last 10 years, water demands have dropped 20 percent. The message right now is to continue using water efficiently – especially for farmers and residents of Healdsburg and communities to the north, which rely on releases from Lake Mendocino.”
Because rain is expected and water is still coming into the Russian River from its tributary streams, it is unlikely that flows will drop to the levels indicated below. However, these flows are permitted under Decision 1610 in order to preserve water storage in a critical year designation:
- Upper Russian River (Between Lake Mendocino and the confluence of Dry Creek and the Russian River near Healdsburg): 25 cubic feet per second (“dry” minimum flows currently in effect are 75 cfs; “normal” minimum flows are 185 cfs)
- Lower Russian River (between the confluence of Dry Creek and the Russian River to the Pacific Ocean): 35 cfs (“dry” minimum flows currently in effect are 85 cfs; “normal” minimum flows are 125 cfs)
- Dry Creek (between Lake Sonoma and the confluence of Dry Creek and the Russian River): No minimum flow change (“critical,” “dry” and “normal” minimum flows are 75cfs)
The water agency’s two water supply reservoirs, Lake Sonoma and Lake Mendocino, continue to provide a reliable, secure source of drinking water for more than 600,000 residents in portions of Sonoma and Marin counties despite this year’s dry weather.
Below are reservoir water supply levels as of March 1:
Lake Sonoma: 83 percent of water supply capacity
Lake Mendocino: 91 percent of water supply capacity. Note: Because the amount that can be stored in the lake for water supply changes seasonally (increasing as we approach the dry summer season), the current level compared to summer (May 10 – Oct 1) water supply capacity is 56%. (See attached graph.)
“It’s in years like these that we really appreciate our reservoirs. the water agency will be managing releases as efficiently as possible and if people continue to use water wisely, we will have enough to meet multiple uses, including the release of water for the fall migration of Chinook salmon,” said Assistant General Manager of Operations Pam Jeane. “Ideally, we’ll start next fall with sufficient water in Lake Sonoma to meet a second dry year, if necessary.”
In 2008, the National Marine Fisheries Service (NMFS) issued its Russian River Biological Opinion. Biologists with NMFS concluded that minimum flow levels in the Russian River and Dry Creek during the summer (as established by Decision 1610) are too high for young coho salmon and steelhead. NMFS biologists believe that reducing summertime flows in the Russian River and Dry Creek would provide better fish habitat by reducing velocity.
The biological opinion requires the water agency to seek permanent changes to the required minimum flows and, until those change requests are considered, annually request a reduction in minimum flows in the Russian River. In 2010 and 2011, the water agency sought – and the State Water Board granted – reductions in minimum flows to comply with the biological opinion.
Decision 1610 established a measure (known as a hydrologic index) that determines the water supply condition. The hydrologic index for the Russian River system is based on inflow into Lake Pillsbury, which is located outside of the Russian River watershed. the water agency is reviewing alternatives to this hydrologic index to determine if another index would more accurately reflect water supply conditions in the Russian River.
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