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Environment | Water

Scientists Measure What Dams Have Done to the Elwha

PORT ANGELES, Wash. — Signs abound on Washington’s Olympic Peninsula that decades’ worth of talk of removing the Elwha River’s two dams is giving way to action on an unprecedented scale.

Roads are closed off. Construction crews and equipment are moving in to start the world’s biggest dam removal project.

Scientists are here, too, preparing for when the dams come down. In a side channel of the Elwha, nestled between the two dams, one of those scientists, Sarah Morley, crouches by the river, surrounded by buckets, bottles and nets. She’s one of a team of scientists from the National Oceanic and Atmospheric Administration’s Northwest Fisheries Science Center that’s trying to record the food web of this river, which channels rainwater, snowmelt and glacial runoff from Olympic National Park‘s mountains and forests, past the two dams, and into the sea.

The scientists are trying to figure out who’s living here, who’s eating whom and how that might change once the dams are removed.

Undamming the Elwha

  • Part I (today): Scientists are getting the “before” shot of the Elwha so they can see how things change once the river is dam-free.

  • Part II (Wednesday): Keeping track of river otters to better understand a changing river and its impact on the forest ecosystem.

  • Part III (Thursday): The Lower Elwha Klallam Tribe is counting on hatcheries to hasten the return of its subsistence fisheries.

Morley reaches into one of her buckets where several rainbow trout circle agitatedly.

“So we’re going to do something called ‘gastric lavage,’ which is a non-lethal way of collecting their stomach contents,” she says. “Kind of like if you go to the hospital room and they make you throw up if they think you’ve ingested something toxic.”

Morley grabs a fish and squirts water on its snout until it opens its mouth. Then in goes the syringe and more water is used to flush out the brown gunky contents of the rainbow trout’s belly.

While Morley and her team are trying to map out what’s going on at the bottom of the food chain in this river, another team from NOAA is trying to figure out how the river itself is going to physically change once the dams come out.

And this is where the story gets personal. It’s my first time in hip waders, clambering over some pretty big slimy rocks in about three feet of water. I’m off to catch up with the other team of scientists when, before I know it, I’m on my back in the Elwha. I’m soaking wet, and so is my equipment.

George Pess leads NOAA’s restoration monitoring team on the Elwha. He explains that I didn’t slip simply because I’m a klutz (although that’s a big part of it). It’s about the rocks, which he and his team are measuring in this section of river.

Most of them are the size of softballs to basketballs and larger.

“It’s definitely a sediment-starved river,” Pess says. “What that means simply is that all the smaller material eventually kind of goes away with nothing coming upstream.”

Rivers are like conveyor belts. They move massive amounts of sediment. When the dams went in, that sediment flow was blocked. Now there’s about 23 Empire State Buildings’ worth of smaller-grained material built up above the dams, with mostly big, slippery rocks left below.

And that’s not just a problem for clumsy journalists.

When a female salmon spawns, it turns to its side, moves its tail, and projects the water down and digs a nest, Pess explains.

“Now, if you have really large material, it’s going to be really hard for a smaller fish to actually dig through that, almost like a sheet of concrete,” he continues.

Once the dams come out, water will flush the sediment down the lower river and into the Strait of Juan de Fuca. Scientists predict some wildlife mortality initially, but big picture, that sediment will eventually rejuvenate the estuary and restore critical spawning habitat for salmon.

It turns out the sediment in a river is almost as important as the water.

Fix Your Coordinates

There are no salmon above the dams anymore but every year steelhead and chinook, coho, pink and chum salmon bump their noses at the base of the lower dam, as if they know what they’re missing out on.

Population numbers of these fish have steadily declined since the dams went in. But Pess says things will turn around once the dams are out.

“I think what you’ll see is a rapid rate of change with these species in terms of going from, let’s say, hundreds to perhaps thousands and even tens of thousands within several decades,” he says. “It may not be a quick turnaround in the sense of somebody’s life but it’s a quick turnaround for ecological recovery.”

(Story and audio by Ashley Ahearn. Video and photos by Katie Campbell).

(Coming Wednesday: Keeping track of otters to better understand a changing river.)

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