The Delta Cross Channel Gates on the Sacramento River near Walnut Grove will be closed today at 10 a.m. as an experiment to help salmon.
The closure at this time of year is unusual, but is intended as an experiment to see if more fall-run chinook salmon make their way back to the Mokelumne River to spawn naturally and in the state-operated hatchery on the river.
Fishing groups, which called for the trial, celebrated the move in a letter to the U.S. Bureau of Reclamation.
"It will virtually guarantee that the Mokelumne Hatchery will produce at least 6 million fall-run salmon smolts for the ocean fishery," Roger Thomas, chairman of the Golden Gate Salmon Association, and others wrote in the Sept. 29 letter. "It is truly worth a celebration."
Reclamation operates the massive gates and the cross channel. Built in 1953, the system diverts fresh water from the Sacramento River to the interior of the Sacramento-San Joaquin Delta to control salinity that affects water diversions for urban and agricultural use.
It has recently been proved, however, that the open gates contribute to "straying" by migratory salmon both adults traveling upriver to spawn and juveniles migrating to the ocean. This has contributed to a loss of genetic diversity in the salmon runs and more predation of young fish as they travel to the sea.
The closure is expected to continue until Oct. 14 at 10 a.m.