FRESNO - It all starts Thursday with a gentle surge of water to be released from Friant Dam, northeast of Fresno, into the San Joaquin River.
A massive, unprecedented and unpredictable river restoration project will begin, reawakening miles of dried riverbed and salmon runs that have been extinct for six decades.
Now, in a nine-year effort that could cost up to $1.2 billion, the 350-mile San Joaquin will be reconnected with the Pacific Ocean. Salmon, which once teemed in its waters, may again migrate from near Fresno to the ocean.
The project begins with test releases to determine how the river will respond. Engineers then will widen the riverbed in some places and dig new channels around obstacles.
In recent years, government agencies across the nation have attempted other big-river restoration projects, from the Penobscot River in Maine to the Klamath in Oregon. But nobody is restoring a big, salmon-supporting river this far south - or a river as damaged as the San Joaquin.
"I've never seen anything like this on this scale," said Bay Area-based biologist Chuck Hanson, a longtime fisheries consultant and now a member of an independent advisory committee on the San Joaquin restoration.
Farmers will lose water
Not everyone relishes the challenge.
Under terms of a complex, controversial court settlement, east-side valley farmers - 15,000 of them, cultivating 1 million acres from the center of the valley to the foothills - will give up some of their irrigation water so the San Joaquin can be reborn.
The water loss comes at a dark moment for California agriculture.
The valley's west side - a national symbol for farmers battling environmentalists over water - already is reeling from three years of drought and restrictions to preserve a rare fish species, the Delta smelt.
Though river restoration will send more water downstream into the west side, farmers in the hard-hit Westlands Water District would get no share. Some could benefit from river water that seeps into the water table, but the potential benefit is unknown.
There are plans to pump some replacement water back through an aqueduct from the Sacramento-San Joaquin Delta, where the river ends, to help east-side farmers. But that water may instead be needed downstream to ease problems for threatened fish, such as the Delta smelt.
For worried farmers, the restoration boils down to a single question: Can the government rebuild this river without crippling the valley's internationally known farming industry? Environmentalists and scientists think the odds are good, but nobody knows for sure.
Waste of taxpayer money?
Farmers have dreaded this moment since 1988, when environmentalists sued to rescue the San Joaquin. Decades earlier, it was the river that rescued farms. Friant Dam was built in the 1940s to capture most of the river's water and irrigate dying farms in Merced, Madera, Fresno, Tulare and Kern counties.
The river and its salmon runs were deliberately sacrificed, although even then the state fish and game code required a stream of water beyond the dam for the native fish. Environmentalists used that provision as a cornerstone in their 1988 lawsuit.
Farmers fought the suit for 18 years, but decisions in the case were consistently going against them. They were running out of options. So they cut a deal in 2006 - a compromise intended to restore the river and salmon runs but preserve most east-side farming.
Three years later, some farmers have begun to doubt they will see much river water circulating back from the restoration to their fields. And they wonder whether salmon, a cold-water fish, will even survive in a warming climate over the next century.
Farmer Kole Upton, one of four people who negotiated the restoration deal in 2006, has changed his mind about the settlement for many reasons, including the salmon issue.