The American River is flowing higher through Sacramento today, part of a federal effort to help young salmon at risk during the drought.
The U.S. Bureau of Reclamation doubled water releases from Nimbus Dam from 500 cubic feet per second to 1,000 cfs. The increase began Wednesday night and is expected to reach 1,000 cfs before returning to 500 cfs just before midnight today.
Biologists call the release a “pulse flow.” It is intended to help some of the wild-spawned fall-run chinook salmon eggs that became dewatered in their gravel nests, or redds, when Reclamation reduced flows in January. That action was taken to conserve water stored in Folsom Reservoir for Sacramento-area communities.
It turns out that not all of those stranded salmon eggs perished as the river shrank. Tom Gohring, executive director of the Sacramento Water Forum, said many were able to survive on the small amounts of water and oxygen that remained within the gravel and hatched into “alevins,” a kind of embryo life stage. The pulse flow is intended to wash those alevins into the river so they can transform into fry, the first finned stage of salmon life.
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“Because the gravel is wet and not submerged, they are stuck,” Gohring said. “Biologists believe this pulse flow will help them get out of the gravel.”
It also will help transport salmon fry that have emerged farther downstream, where they may have access to more habitat.