By Sonoma County Water Agency
SANTA ROSA — Thanks to the “March miracle” rainfall, Russian River water supply conditions on April 1 will change from “critical” to “normal” under the Sonoma County Water Agency’s water rights permits and State Water Resource Control Board 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.
“March has delivered our water supply system with much needed rain. The rain has resulted in significant inflow into Lake Pillsbury, to the point where we are now back into a ‘normal’ water supply scenario through at least May 1 when the water supply condition will be reassessed,” said Water Agency Assistant General Manager of Operations Pam Jeane. “We would like to see more rain in the coming month so our reservoirs can continue to fill for the upcoming dry season. It is important that our community continue using water efficiently — especially farmers and residents of Healdsburg and communities to the north, which rely on releases from Lake Mendocino.”
This “normal” designation means the Water Agency will not reduce Russian River flows in April as called for under the previous dry or critical designations. Minimum flows for April instead will be implemented as follows:
- Upper Russian River (Between Lake Mendocino and the confluence of Dry Creek and the Russian River near Healdsburg): 185 cubic feet per second
- Lower Russian River (between the confluence of Dry Creek and the Russian River to the Pacific Ocean): 125 cfs
- Dry Creek (between Lake Sonoma and the confluence of Dry Creek and the Russian River): 75 cfs
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.
Reservoir water supply levels as of March 30:
- Lake Sonoma: 94 percent of water supply capacity
- Lake Mendocino: 92 percent of water supply capacity. The amount of water that can be stored in the lake for water supply changes seasonally, increasing as we approach the dry summer season).
Russian River Biological Opinion and hydrologic index
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.
In 2008, the National Marine Fisheries Service 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. The Water Agency expects to file a petition to change minimum flow requirements to comply with the biological opinion in early April 2012.
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