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 move by the U.S. Fish and Wildlife Service follows its order Friday that sharply curtailed pumping by state and federal water systems that serve 25 million Californians. That move 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 prompted to migrate upstream by turbid or muddy water conditions.
Biologists suspect the fish began migrating when December rain 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.