The session in Sacramento will be the first of five before the State Water Resources Control Board, which is considering a major boost in the flows. Irrigation districts, city water suppliers and other critics will get their chance as the public hearing moves to Stockton, Modesto and Merced next month.

The board Wednesday released a detailed agenda for the hearing, which will be webcast live. Its staff already has heard plenty of informal comment since the proposal came out in September.

“It will absolutely devastate our economy,” Stanislaus County Supervisor Vito Chiesa said during an October presentation by the state agency. Added Supervisor Jim DeMartini, “Where do you get the authority to just take the water away from the irrigation districts?”

The state board staff said the plan tries to balance the needs of fish and humans, and is much less than what many environmentalists would like to see.

“We don’t view this as an easy task in the least,” Executive Director Tom Howard told the Merced County Board of Supervisors in October.

The increased reservoir releases would help struggling fish in the lower rivers, he said. The agency also aims to reduce salinity in the Sacramento-San Joaquin Delta, which is tapped as a water supply for much of California.

The state board will take written comment until Jan. 17 and could make a final decision in July.

The flows would rise from February through June of each year, when most of the rain runoff and snowmelt take place. The plan calls for boosting the rivers to 40 percent of what they carried before the dam building that started in the mid-1800s. The three rivers combined are at about 20 percent now, but the Stanislaus is already under a higher standard than the Tuolumne and Merced.

The state agency acknowledged that the loss of river supplies would prompt farmers and cities to increase well pumping. Critics say this flies in the face of a recent state law that requires sustainable groundwater use within a quarter-century.

They also say the state’s projection of farm losses – 433 jobs and $64 million in income in an average year – is far too low in a three-county region that grossed about $10 billion last year.

Irrigation leaders agree that some increased flows could help salmon, but they want them targeted to when the fish would clearly benefit. They urge non-flow measures, such as restoration of spawning gravel and reduced predation by non-native bass.

The state board staff said 40 percent is a “starting point,” but the levels could range from 30 to 50 percent depending on conditions.

The Tuolumne River Trust urges at least 50 percent to enhance a stream heavily used by the Modesto and Turlock irrigation districts, along with San Francisco and nearby cities.

Farms and cities could build on their efforts at efficient water use, Executive Director Patrick Koepele said in an email Wednesday.

“River restoration creates jobs,” he added, citing a study on the large project underway on an often-dry stretch of the San Joaquin River upstream of the Merced confluence.

“A healthier river and healthier environment is also a quality-of-life issue,” Koepele said. “We want places for our families to enjoy nature close to home, a place for a father to take his kids fishing, for friends to picnic.”