As the drought progresses in California, and as a dry 2013 left Lake Mendocino in dire condition, the Sonoma County Water Agency and the state are taking action to preserve the region’s water supply.
The State Water Resources Control Board (SWRCB) has approved a petition to change how the water agency manages water supply levels and water release in Lake Mendocino, just northeast of Ukiah.
SWRCB issued an order that will allow the water agency to preserve Lake Mendocino’s diminishing water storage level by managing flows in the upper Russian River according to the reservoir’s water supply conditions. The board’s decision came as a response to the Temporary Urgency Change Petition filed by the water agency Dec. 19.
Lake Mendocino depends on annual rainfall and diversions from the Eel River watershed through PG&E’s Potter Valley Project. And 2013 was the driest year on record in Ukiah, with only 7.67 inches of rain since Jan. 1, 2013, compared to the annual area average of 34 inches.
“The effect of this decision will result in lower minimum flows in the upper Russian River and more operational flexibility for water managers working to preserve every drop of water in Lake Mendocino,” water agency spokesman Brad Sherwood said.
The water agency manages and regulates water supply at two reservoirs, Lake Mendocino and Lake Sonoma, to meet the needs of more than 600,000 people in parts of Sonoma and Marin counties. Since 1986, as mandated by SWRCB, the water agency is required to release sufficient water from the reservoirs to maintain flow rates above designated minimum values along the Russian River. The values change depending on whether the water year is deemed “normal,” “dry” or “critical.” According to water agency Assistant General Manager Pam Jeane, prior to the approval of the temporary change, the agency had to look outside its watershed at Lake Pillsbury to determine release levels for Lake Mendocino.
For the revised flow regime, the agency developed criteria to gauge conditions based on the original state mandate, Jeane explained. “Hopefully that (temporary change) will be much more representative of what is going on in our watershed.”
The order will allow minimum flows in the Russian River between Lake Mendocino and Dry Creek, below Healdsburg, to drop from 75 cubic feet per second to 25 cubic feet per second to prevent the reservoir from reaching unsafe levels.
The low levels in Lake Mendocino are exacerbated, Jeane explains, because flood control precautions require the water agency to leave space in the reservoir in case of large amounts of rain, which reduces the already-small reservoir’s storage capacity.
Communities that rely on Lake Mendocino include Ukiah, Cloverdale, Geyserville, Healdsburg and unincorporated areas of Mendocino and Sonoma counties.
“Making reductions in water releases now could help prevent serious impacts in the future to endangered fish and to communities like Geyserville and Cloverdale,” said water agency Director Mike McGuire in a prepared statement. “Unfortunately, we must assume that the new year will be dry and plan accordingly.”
The water agency is also working closely with the National Marine Fisheries Service and California Department of Fish and Wildlife to make sure a reduced stream flow will not impact migrating and spawning coho, chinook and steelhead.