An appellate court has upheld state rules regulating how hundreds of farmers in Sonoma and Mendocino counties divert water from the Russian River to ward off frost.
The rules, aimed at protecting fish, were struck down in 2012 by Mendocino County Superior Court Judge Ann Moorman, who declared the law to be "constitutionally void" and "invalid."
The state's First Appellate District court reversed her decision in a ruling filed Monday.
The State Water Resources Control Board lauded the decision.
"The board is pleased with the court's unanimous decision upholding the Russian River frost protection regulations," Michael Lauffer, the board's chief counsel said in a statement.
Mendocino County Farm Bureau Manager Devon Jones said the appellate court ruling is a disappointment.
"We felt there was a very good opinion," she said of the overturned ruling.
State regulators created the rules to prevent endangered and threatened salmon and steelhead trout from becoming stranded and dying when farmers pump water from the Russian River to ward off frost. Water is sprayed on vines to create a protective ice shield when temperatures fall below freezing.
The goal of the state rules is to avoid the sudden drops in river flows that can be caused when farmers throughout the river system pump water at the same time.
Several incidents in which rapid declines in river flows caused fish to become stranded triggered the regulations. Fisheries officials estimated some 25,000 salmonids were killed in two April 2008 episodes, one each in Sonoma and Mendocino counties. The incidents coincided with freezing temperatures, state officials said.