One of the biggest beneficiaries has been Lake Shasta, a keystone reservoir of the Central Valley project, which serves California growers.

To make room in Shasta for water from last weekend's storms, the Federal Bureau of Reclamation ramped up releases from 5,000 cubic feet per second to 20,000 cubic feet per second on March 18. It was the first time since 2011 that the bureau released water into the upper Sacramento River at such a rapid rate, said spokesman Shane Hunt.

Officials began slowing the releases again on Wednesday, Hunt said. The rate is expected to return to around 5,000 cubic feet per second by Monday.

"We never got to the point where the increased releases drew the lake down at all," Hunt said. "We just slowed how fast we were gaining."