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Field Notes

Covering the natural wonders of the Pacific Northwest

August 15, 2011 at 10:30 AM

Side channels: the fish spas of the Elwha River

Unnamed and, to most visitors, unknown, the side channels of the Elwha River are a special realm: secluded, quiet, sheltered, they are the river’s spa, where fish go to rest, hide and feed.

Clear, groundwater-fed side channels like these on the Elwha River can be ten degrees warmer than the main stem, giving young fish a tranquil, warm, sheltered environment where they can get bigger and faster, boosting their chances for survival.

Not only are side channels productive, nurturing places for fish, they are a haven for other wildlife. On a recent reporting trip to a side channel in the middle river, I encountered a vision of Eden in mid-summer.

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This side channel was entrancing: quiet, but for the sound of birds, and with water so clear it was like a lens

Lynda Mapes video

The food supply in these side channels is abundant. In this channel, the still waters are alive with water skeeters on the surface, and a whole world of animals in the benthos, or stream bottom.

In the shallows, a mass of salamander eggs attested to the use of these still waters by amphibians. Trickles of cold, clear water from the hill slope joined the side channel, swelling the flow.

Here, beneath the shimmer of the surface, was the secret realm of the shredders and grazers: tiny creatures busily devouring the nutritious litter that rains into the river from the trees above, and periphiton, or slimy layer growing on the rocks and stream bottom.

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The leaves and other nutritious litter rained down from the forest, and slime on the rocks and river bottom are key elements in the food chain, feeding the tiny insects of the benthos that are the primary producers, shredding, grazing, and growing big and fat to in turn become food for fish, amphibians, birds and other life.

Lynda Mapes photo

Side channels are havens not only for fish, but other wildlife too. Walking up one side channel I encountered a fledgling dipper, snoozing on the end of a log, utterly unconcerned as I sloshed past. The aquamarine color of the water, caused by glacial flour in the water column, told me that this side channel was influenced not only by groundwater, but also, at high flows, by water from the main stem.

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A fledgling dipper rests on the end of a log in this side channel.

Lynda Mapes photo

The river’s only aquatic songbird, dippers are named for their habit of dipping up and down as they stand by the riverside between underwater flights to forage for food. Its call is the music of the river, punctuated by the the timpany of the tumbling current.

The banks were twined with wild roses, their petals pink and floating on the water, and perfume sweet on the air. Thickets of salmonberry were hung with fat fruit. A swallowtail butterfly opened and closed its glamorous wings, warming itself in a patch of sun, brilliant amid the cool green of the canopy of alder and cottonwood that closed overhead.

“The importance of these side channels has been overlooked, even by biologists,” noted Mike McHenry, habitat biologist for the Lower Elwha Klallam tribe, as he helped scientists George Pess and bio-statistician Martin Leirmann of the National Marine Fisheries Service Northwest Science Center in Seattle take measurements of the side channel.

When the productivity estimates for the river were extrapolated post dam removal, the fish these places are expected to produce weren’t even tallied, McHenry noted.

Nobody knows how many fish the restored Ewlha will really produce, McHenry said But it is surely even more than the forecast 400,000 fish calculated without considering the side channels.

Scientists have come to better understand the role of these side channels as salmon bedrooms, and to appreciate the critical role these sheltered areas may play when the Elwha dams start to come down, beginning next month.

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George Pess is leading an inter-agency team of scientists doing baseline monitoring on the Elwha, including the mapping of side channels. Here, Pess uses a tree for a desk as he logs data on a recent trip to the back country of the Elwha.

The river will at first be transporting gigantic loads of sediment now trapped behind the dams — some 24 million cubic yards, making the water inhospitable to fish, and possibly smothering the fishes’ food supply on the the bottom.

It may be as long as ten years before the river settles down to normal. In the meantime, fish are expected to shelter in the less turbulent side channels. During high flows, water from the main stem will enter the side channels, bringing sediment loads, too. But in lower flow months, these places — dozens of miles of primo, sheltered habitat — will be a place where clear, sheltered waters stoke recovery of fish populations.

It was easy to see how that would work, as I stepped from the mayhem of the main strem, carrying the runoff from some 200 percent of average snowpack, to the quiet, sheltered world of the side channel.

I watched as McHenry, Pess and Leirmann worked their way down the channel, using a laser to measure its longitudinal profile. They are working with other scientists to map the Elwha’s side channels in detail, including their size, location, bed height and pool depth.

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Scientists have been mapping side channels of the Elwha River, in preparation for dam removal. They want to track how the river changes once the dams come down.

Lynda Mapes photo

To date, scientists have mapped more than 10 miles of side channels in the upper river, about 8 miles in the middle river, between the dams, and nearly five miles in the lower river. The side channels they have documented, some 23.4 miles in all, Pess said, adding that’s surely an underestimate of the total amount of this special type of habitat in the river today.

When the dams come out, the river, running free again, is expected to cut more side channels, adding to the productivity of the Elwha.

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