The bureau's outlook came as federal water managers prepare to announce how much water will be available for Central Valley farmers this summer.
Johnny Amaral, deputy general manager at Westlands Water District, said federal officials have told his district not to expect any surface water this year. Westlands distributes federal water to hundreds of farms in the San Joaquin Valley — the nation's most productive agricultural region.
"What they've told us is to plan for zero," said Amaral, who blames environmental regulations that protect endangered fish for allowing water to flow out to sea rather than being captured in reservoirs.
"That's not a good situation," he said.
Salmon can't be blamed for the drought that has devastated their numbers, said John McManus, executive director of the Golden Gate Salmon Association. Much of the runoff from recent storms is carrying recently spawned salmon from rivers to the sea, he said.
The U.S. Bureau of Reclamation says it is too early to determine specific water allocations in the valley.
The bureau said Lake Shasta — the state's largest reservoir, located in Northern California — is 68 percent full, while San Luis Reservoir in Central California is at 20 percent of its historical average for this time of year.
Federal authorities operate the Central Valley Project, part of a system of canals and reservoirs that delivers water from throughout California.
The state Department of Water Resources, which manages part of California's vast water system, said in early December that it anticipated releasing 10 percent of supplies sought by farmers this year — half of the last year's allocation.
David Murillo, a regional director at the U.S. Bureau of Reclamation, welcomed the strong Sierra Nevada snowpack at the start of winter and the parade of El Nino storms that doused California following four years of historic drought.
"With this promising news and El Nino storms beginning to materialize, we are feeling encouraged," Murillo said in a statement. "However, storage in our reservoirs remains low, and we must be prudent."