Water diversion gates in the Delta near Walnut Grove to close Monday morning

Water diversion gates near Walnut Grove in the Sacramento-San Joaquin Delta will close Monday morning, sealing off a shortcut important to boaters.

The closure of the Delta Cross Channel Gates is expected to occur at 9 a.m. Monday, according to the U.S. Bureau of Reclamation, which operates the gates. The closure is required to meet water quality standards in the Sacramento River. The gates are closed when water monitoring stations indicate salty conditions downstream that could be improved if less fresh water is diverted.

Fall-run chinook salmon migrating upstream to spawn also will benefit. When the gates are open, salmon have a tendency to stray from their migratory route, often ending up in the wrong stream.

“More Mokelumne River salmon will find their way home to spawn with the gates closed, which is a good thing,” said John McManus, executive director of the Golden Gate Salmon Association.

The gates were built in 1953 as a device to divert Sacramento River water into the interior Delta, then to state and federal diversion pumps near Tracy. Their operations have been adjusted in recent years after research demonstrated negative effects for native salmon species.

The gates also came to serve as a useful shortcut for boaters moving between the Sacramento and San Joaquin rivers. The gates were closed Thursday afternoon to meet the water quality standard, but were scheduled to reopen at 3 p.m. Friday to accommodate weekend boaters. Monday’s closure is expected to continue until further notice.