FRIANT -- Several piercing blasts from an air horn Wednesday evening heralded the historic release of water from Millerton Lake for the eventual restoration of the San Joaquin River.

The horn offered a five-minute warning to anyone downstream before a pair of 18-inch valves at the base of Friant Dam were opened at 5:54 p.m., sending jets of water roaring into the river at the rate of 185 cubic feet -- or about 1,400 gallons -- per second.

The federal Bureau of Reclamation is releasing the water as part of a settlement that Valley irrigation districts, environmentalists and the federal government approved three years ago. The goal: to restore an uninterrupted, year-round flow of water to parts of the river that have been mostly dry since Friant Dam was completed in 1944, so that salmon can return.

The water rushing through the valves is in addition to water already flowing through the Friant Dam powerhouse turbines, bringing total releases to 350 cubic feet per second. That's what's required under the terms of the 2006 legal settlement intended to restore a salmon run to the San Joaquin.

Earlier Wednesday, farmers and others unhappy with the river restoration staged a protest at Friant Cove, about two-thirds of a mile downstream from the dam. Calling themselves Families Protecting the Valley, the group fears the restoration efforts will eventually dry up their allocations of water from Millerton Lake and force them to pump more water from an already stressed underground water table.

The group's spokesman, Chowchilla-area farmer Kole Upton, was one of the agriculture negotiators who signed off on the restoration settlement three years ago. Now he's a vocal opponent because, he said, environmental groups reneged on pledges to help protect agricultural water supplies.

"Over the last three years, the environmentalists have initiated lawsuits over pumping in the [Sacramento-San Joaquin] Delta that takes away the ability to recirculate that water back to Friant," Upton said. He also blamed Congress for failing to allocate any money for resupplying water back to Friant.

Another of the group's members, Fresno farmer and businessman Bob Smittcamp, said the effect was to negate the very things farmers thought they agreed on.

"We approved a deal, and then they changed the deal," Smittcamp said.

Upton said he expects that the loss of agricultural surface water to river-restoration efforts will force farmers on the east side of the Valley to idle between 200,000 and 300,000 acres -- and that that will increase as farmers' pumps dry up.

Jason Phillips, who is managing the San Joaquin River restoration program for the Bureau of Reclamation, said the protesters' concerns have merit.

A plan for bringing water from the delta back to Friant water users is being developed, but Phillips acknowledged that lawsuits and environmental rulings over pumping water from and through the delta "will make it more challenging" to recirculate water.

Tony Buelna, the Bureau of Reclamation's chief of operations at Friant Dam, said the additional water would raise the river's level by a couple of inches. The current flow rate will continue through October, then double to 700 cubic feet per second for the first two weeks of November. This will enable water officials to see how the river reacts, how far the water will carry downstream, and how much water soaks into the riverbed.

Except for flood releases, water will be held in check from mid-November until February, when the next stage of river restoration is scheduled. That would bring the flow to about 1,600 cubic feet per second. That's still short of the historic capacity of the channel -- 8,000 cubic feet per second.