Crews weed Yakima River to clear stargrass, help salmon find gravel

A frog hopped across the Yakima River near Benton City Monday afternoon, jumping from water stargrass plant to water stargrass plant before falling through the thick vegetation to disappear with a splash.

Rachel Little, a biologist with the Benton Conservation District, said she’s seen birds walk across the water on the plants this year.

The drought of 2005 was a bad summer for stargrass in the Yakima River. “This is way worse. I’ve never seen it like this,” she said.

The thick growth that carpets the river from bank to bank muffles the sound of the water. It has kept kids from floating inner tubes down the river this year — the ride is too slow. Fishing is no good with lines that constantly tangle in the plants.

But what the stargrass is really bad for is salmon.

The plant has grown an interwoven root mass that’s three inches deep, which will make it impossible for fall chinook that return to the area near Benton City to spawn. They can’t get down to the gravel at the bottom of the river to sweep it aside and make a depression to lay their eggs.

Little is determined to clear as much of the stargrass as possible by the end of September, right before fall chinook should be ready to spawn.

On Monday, a crew of 10 workers from the Washington State Department of Ecology Conservation Corps, most of them AmeriCorps volunteers, spent the day in the river. There would have been more, but some were diverted for firefighting. Little has recruited Mid-Columbia Fisheries Enhancement Group staff and Central Washington University interns this season as well.

Workers reached to the bottom of the river to pull up a mass of water stargrass by its roots and then heaved it up out of the water onto canoes or barges. Local farm dog Buster kept them company, hopping aboard barges for rides through the water.

“It’s like weeding, but underwater,” Little said.

By midafternoon, Benton City farmer Dale Harkins had used his tractor to haul off more than 20,000 pounds of sopping wet stargrass that workers had pulled out of the river since morning. He piled it up to be used as compost, some by him, but most to be given away by the Benton Conservation District.

Last week, the second week of work to remove stargrass, the pile was about 20 feet long and four feet wide.

“The compost is a bonus,” Harkins said. “My real goal is to see the river is useable for fish and wildlife.”

Little has used volunteers other years to pull up water stargrass, one year clearing about an acre. The result was a patch of river that had 30 salmon nests, or redds.

This year her goal is to clear two acres.

“I do believe if we can open up enough spawning habitat, that if our Lower Yakima salmon can get here, they can be successful to spawn,” she said.

Many times salmon will wait at Bateman Island in the Tri-Cities until the Yakima River cools to at least 73 degrees, but this year even the Columbia River is warm and salmon are perishing.

If they do make it up the Yakima River and cannot access their usual gravel beds, they may die without spawning or try to move upstream in search of another area. The stress may make them less successful at spawning if they do find another suitable area.

Water stargrass is a native plant, but it is behaving more like a weed, taking over areas of the Yakima River.

Each of the dozen years Harkins has farmed along the Yakima River he’s seen more and more of it, he said.

It’s easily visible in wide swaths along the edges of the the Yakima River at Harkins’ farm. But it also is abundant in the middle of the river, where the current makes the plants, which can grow six to eight feet tall, lay horizontally in the water.

Each leaf that’s visible above the water is just the tip of the iceberg, Little said.

This spring had perfect conditions for the plant to proliferate. The amount of water in the spring determines how much stargrass there will be in the summer. This year the Yakima River flow was low early in the spring and the weather was unusually warm. The delicate, yellow star-shaped flowers bloomed three weeks early.

“The stargrass started early and its grown exponentially since then,” Little said.

Not only has the Yakima River been warmer than usual, with temperatures of 84 degrees recorded in the river at Kiona, but the stargrass slows down the flow of the water, allowing the sun to heat it up even more.

The stargrass also depletes the river of oxygen needed by migrating salmon, including summer chinook, passing by on their way upriver.

During the day the plants give off more oxygen than they consume. But at night, when salmon tend to migrate, the dissolved oxygen levels are low enough that salmon not already deterred by warm river temperatures may be discouraged from migrating.

“The flows should be higher and a lot faster,” said Josh Perry, the crew supervisor for the Washington Conservation Corps. “The water is amazingly warm, almost pool temperature, which is disturbing.”

In addition to stargrass, his crew pulled debris out of the water — a tire tractor, a refrigerator door and a bicycle.

At the start of the third week of clearing stargrass Monday, the water flow had improved enough in some places that Harkins had provided anchors he had welded together to keep rafts from floating downriver as they were stacked with stargrass.

Those who want the composted stargrass and have the means to haul it away can contact the Benton Conservation District at 509-736-6000. The district also provides technical expertise on other conservation issues, primarily on private land, including on irrigation issues.

This story was originally published August 17, 2015 at 10:36 PM with the headline "Crews weed Yakima River to clear stargrass, help salmon find gravel."