Pete Lucero with the Bureau of Reclamation says it closed the Delta Cross Channel gates near Walnut Grove on Thursday and Friday and will likely close them again today.
"When open, fish have a tendency to migrate through there and they may get lost through the Delta system," says Lucero. "Those fish would normally travel either upstream or downstream on the Sacramento River."
The closure of the channel gates keeps Sacramento River salmon from migrating through Snodgrass Slough into the nearby Mokelumne River.
Lucero says closing the gates increases the amount of water flowing out to the Bay. That helps keep salinity levels below Delta limits set by the state of California.
"Water quality within the Delta at certain points within the Delta must meet a certain standard. In order to do that fresh water needs to flow to the Bay to meet those standards."
Channel access to the Mokelumne river from the Sacramento River will likely be closed until spring.