Federal wildlife officials ruled Tuesday that water exports from the Sacramento-San Joaquin Delta will be allowed to increase again, following signs that the threatened Delta smelt may be out of harm's way.
The U.S. Fish and Wildlife Service on Friday ordered steep flow reductions at state and federal pumping systems near Tracy that divert Delta water to 25 million Californians. The order came after smelt continued to be killed, or "salvaged," in the pumps.
But on Tuesday, the agency allowed water diversions to increase again. It did not completely lift the pumping limits, but restored about 60 percent of the diversion volume lost after Friday's cut.
"No Delta smelt have been reported as salvaged since February 6, 2013, suggesting this year's unusual ... event may be over," the agency wrote in a determination letter posted online.
Smelt, a finger-length fish native to the Delta, are triggered to migrate upstream by turbid or muddy water conditions. Biologists suspect the fish began migrating when December caused a pulse of turbid runoff to move downstream in the Sacramento River. The water systems were taking advantage of the same pulse to divert a lot of water, which may have drawn the smelt too near the pumps.
The California Department of Water Resources and U.S. Bureau of Reclamation, which operate the Delta pumps, have rapidly approached an annual Delta smelt mortality limit set under the Endangered Species Act. The Fish and Wildlife Service warned that it may restrict diversions again if smelt deaths resume.