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02.02.11

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Rushin' Rivers

Lake Sonoma flows and flood control— not a pure science?

By Juliane Poirier


Sustaining a "natural" flow of water in tributaries of the Russian River is tricky business. If too much flows too fast, fish eggs nested in the gravel, aka redds, can get scoured, as can the banks of the waterway (aka erosion).

Flow can be altered abruptly by storms and by releases from the Warm Springs Dam, a 30-million cubic-yard dam created by the Army Corps of Engineers for flood control and water supply. The resulting Lake Sonoma can store 381,000 acre-feet of water and release up to 29,600 cubic feet per second (cfs), and it's the Corps of Engineers who decides how and when water escapes.

But not everyone is pleased by Corps decisions. One angry Santa Rosa fisherman complained to me that the Corps a few weeks ago "blew out fishing on the Russian River just as the conditions were getting good." The fisherman, choosing to remain anonymous, wrote, "The flow increased from 160 cfs to 2,000 cfs in 24 hours. It chased fisherman up the bank and could have washed Chinook, coho and steelhead redds out of Dry Creek's main stem" because the release "had no relationship with the weather and natural stream flow at the time."

Did the redds get blasted out by this?

When I ask this of Bill Hearn, National Marine Fisheries Service biologist, he pointes me to the Russian River Biological Opinion, a NMFS paper that claims scouring of coho salmon and Chinook salmon redds is likely to be caused when releases into Dry Creek are at 5,000 cfs. Hearn summarized by saying that "most redds in the three-mile segment between Warm Springs Dam and Pena Creek are scoured during major release operations." Not good for fish.

Peter LaCivita, a Corps biologist, defends the releases determined by those he refers to as the Corps' "water-management folks in Sacramento" who "look at the projected rainfall and at how much water is in the flood pool, and try to release enough water from the dam to get to the bottom of the flood pool before the rain starts filling up the reservoirs."

When asked whether the fish get any consideration in the releases made last week, for example, LaCivita says, "I believe we went up to 1,700 cfs last week, and we did maintain that release at that level long enough to get some fresh gauge readings below the dam and to calibrate our flows, then ramped back down to much lower numbers after that."

Was damage done to redds during that flooding? "Flood control releases have some impact to steelhead and salmon in Dry Creek," Hearn claims, "limited to the more upstream reaches." According to Hearn, the Corps has agreed to habitat restoration activities to mitigate impacts in more downstream reaches of Dry Creek.

What about the Russian River between Healdsburg and the mouth of the Russian River at Jenner—are the salmon and steelhead adults, juveniles or eggs harmed there by these gushes of water? "The flood releases," Hearn says, "very likely do not have significant impacts" on these fish in the main stem of the river.

As for ruined sport-fishing opportunities, Hearn explains that the NMFS, though it "administers the Endangered Species Act for marine and anadromous species, the Magnuson-Stevens Act which addresses conservation and protection of commercially harvested fish species and the Marine Mammal Protection Act," doesn't have the regulatory muscle to force the Corps to alter releases unless endangered fish species are being adversely impacted.

"We readjust releases depending on what circumstance calls for," says LaCivita. "I think you need to appreciate the fact that storms are part of the ecosystem, that higher flows are needed for spawning salmon swimming upstream to spawn, and that you need a certain amount of flow to move the finer sediments out of the gravel where the fish spawn. A pulse flow of 1,700 cfs at best is not unlike a routine storm." Very serious storm conditions, LaCivita points out, have created flows of 35,000 cfs at Guerneville.

"The two dams, Lakes Mendocino and Sonoma, control only 15 percent of the entire runoff for the Russian River watershed," he says. "And there's some art to this. It's not a pure science."


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