When California state biologists crested a sandbar along the Feather River on Tuesday morning, they expected to find at least some of the water that just a day before had raged through the channel, too deep to stand in – and plenty of fish needing to be rescued.
Instead, to their chagrin, the flows powering down Oroville Dam’s badly damaged main spillway into the Feather River had been throttled back so quickly Monday that the whole sandbar was now dry.
“Oh, no,” said biologist Alana Imrie.
In one low spot, the sand-specked carcass of a suffocated 14-inch steelhead lay in the sun beside several smaller but equally dead baby fish. Some were Chinook salmon, a species central to California’s $1.4 billion commercial and recreational fishing industries.
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Imrie and her colleagues trotted over to look for survivors. They found a handful, including a palm-sized wriggling lamprey. These were placed into a bucket filled with water. The fish later would be measured and released into the river.
Rescue efforts such as these will take place over the next several days along the Feather River below Oroville Dam’s broken spillway. Through at least Saturday, teams of state biologists in 10 boats will patrol the river from just below the dam nearly to its confluence with the Sacramento River at Verona, north of Sacramento. The crews will use photos shot from helicopters to focus in on low spots in the floodplain adjacent to the river, where thousands of fish may be stranded in small ponds. Just a couple of days earlier, the swollen Feather had thundered through its channels, inundating low-lying areas along its route.
In a matter of hours Monday, engineers at the troubled dam ramped back outflows on the main spillway from 50,000 cubic feet per second to nothing. The Feather River below the dam is still flowing, though at levels closer to what’s typical in summer, thanks to water releases from a series of small reservoirs below the dam.
Federal fisheries regulators had urged the state Department of Water Resources, which operates the dam, to taper the spillway releases more gradually to prevent as many fish from getting stranded. DWR officials said they complied with those suggestions as best they could, but haste still had to be a priority.
The break in the wet weather this week gives engineers a critical window to assess damage to the 3,000-foot concrete spillway that fractured Feb. 7, and now sports a massive cavern in its midsection. Heavy equipment operators also are working to clear out a massive mound of concrete, earth and debris that formed in the channel below the spillway as it eroded. The mound was so extensive it had raised channel levels to the point that the dam’s hydroelectric plant can’t function. While the spillway serves as a critical flood-control valve during California’s rainy season, the plant is the dam’s primary outlet the rest of the year.
Efforts to clear the channel below the dam are already paying off, said Nancy Vogel, a spokeswoman for the California Natural Resources Agency.
The water in the channel dropped 23 feet in less than a day, which should be enough to get at least one of the turbines up and running, perhaps as early as Thursday. Electrical crews are working to get transmission lines from the power plant reattached to the power grid, Vogel said.
The plant, when fully operational, can release about 14,000 cubic feet per second. While just a fraction of what the main spillway can release, outflows from the plant would be enough to handle about half of the inflow expected as the abundant Sierra snowpack begins melting into the reservoir in coming weeks.
With the spillway closed Monday, the Feather River below the dam receded much faster than a river typically would after a flood, biologists said. There wasn’t time for many of the fish in flooded areas to reach the safety of the main channel.
“They’ve endured floods before the dam was built, but this was such a sudden decline,” said Clint Garman, an environmental scientist with the state Department of Fish and Wildlife, the agency coordinating the rescue.
Any little pond along the river channel – even deep ruts carved by tires in dirt roads along the river – might contain a few dozen fish. In just one pond that formed in 3 inches of water in the ruts on one such road, biologists rescued 23 baby Chinook salmon.
Across the river, at the sandbar where Imrie’s team found the steelhead on the rapidly drying riverbank, biologists quickly found two knee-deep ponds nestled in hollows.
Ringed with blackberry thorns and slippery rocks, the ponds were writhing with dozens of fish – many of them fall- and spring-run Chinook salmon just an inch or two long. The ponds also held a handful of bronze Sacramento suckers nearly 2 feet long and a couple of ocean-bound steelhead longer than a foot.
One of the biologists, Marc Beccio, wore a backpack attached to a hand-held rod that allowed him to stun the fish with electricity. The other biologists would swoop in with nets and scoop up the fish that floated to the surface.
“We got here just in time,” Beccio said. “But barely.”