Something is about to happen on California's second-longest river that hasn't happened this time of year since Harry Truman was president.
Water is going to start flowing down two stretches of the San Joaquin that have been sucked dry since Friant Dam began diverting most of the river into two giant irrigation canals.
Today dam managers will crank up releases of water into the San Joaquin as part of an ambitious restoration program intended to return chinook to the once salmon-rich river by late 2012.
The increased flow, which will last six weeks, is the first of several years of test releases to help scientists gauge the effect of restoring year-round flows to a river that shrivels to dust for 60 miles.
Immediately below the dam, which sits in the Sierra foothills northeast of Fresno, the release will be barely perceptible.
"It's hard to visually see that change," said Monty Schmitt of the Natural Resources Defense Council, which led a two-decade-long court fight to let the San Joaquin keep more of its water.
"The real change is going to happen 38 miles downstream when the water gets to Gravelly Ford, where it's bone dry and the river will slowly creep back into life."
Except during flooding in exceptionally wet years, that and another stretch of the San Joaquin have been dead for more than half a century.
Scientists will monitor the new flow's temperature, depth, water quality and path. Does the renewed river stay in its dusty bed or spread onto adjacent cropland? How do the flows deposit sediment that can nourish salmon spawning beds?
Come spring, another, slightly larger test release will be made.
"This is truly amazing given the number of people who once said it would never happen. And now we are a day away," Schmitt said Wednesday.