A few years ago, biologist Zac Zacavish, a research biologist with the Yakama Nation, decided to float the Yakima River. He’d been part of a project studying water stargrass, and they’d seen a ton of it on satellite images.
But he wanted to see the problem from the river.
He started in Union Gap, just outside Yakima, where the amount of water stargrass looked pretty normal.
“ Water stargrass (was) here and there, kind of tucked away behind gravel bars and slow pockets,” he said.
Then he hit Mabton — about 50 river miles downstream.
“It (was) 100% of the water column, and it's really hard to boat through it. As you're going through that section, you're like, ‘Oh, wow,’” Zacavish said. “That's kinda like the head of the snake, if you will.”
Bits of that stargrass pileup spread downriver. Combined with years of drought, low-flowing water and high water temperatures, water stargrass in the lower Yakima River has absolutely spread like weeds, said Troy Maikis, a habitat biologist in Benton and Franklin counties for the Washington Department of Fish and Wildlife.
In the last few years, thick mats of the aquatic grass have clogged boat propellers, stolen fishing lures, annoyed paddle boarders and killed many salmon.
It’s thriving along over 60 miles of the river. The problem is the worst in the summer, also creating a breeding ground for mosquitoes.
People on the water pointed out the problem and helped show exactly how bad it has gotten, said Michael Porter, the lower Yakima River project coordinator for the Yakama Nation.
“ It's really impacted fishing. I used to talk to fall Chinook fishermen around Bateman Island, and they can't fish in the same areas,” Porter said.
The plant also choked farmers’ water intake systems and fish ladders.
The poor water conditions harm adult and young salmon, known as smolts, Porter said.
“ We see a lot of our fish sitting at the mouth of the Yakima in the Columbia River and never returning up to the Yakima because of these conditions,” he said. “Also, we're losing about 60% to 90% of these smolts in the lower 100 miles of the Yakima River.”
Fish have trouble making it past that dense, weedy forest in the water. The slow river means the water heats up too hot for salmon in the day. Then, at night, the water stargrass sucks out all the oxygen fish need to survive.
“It becomes basically a black hole. It just eats fish,” Porter said.
Removing the Bateman Island causeway in the Tri-Cities should help the stargrass problem at the river’s mouth, he said. The process is expected to start this winter.
Salmon are also no longer able to spawn in the roughly 60 miles where stargrass is thriving. Prior to the stargrass explosion, biologists said they counted around 200 redds, or salmon nests. Now, if the fish can make it, they have to travel farther upstream to spawn.
Getting water stargrass under control
The increasing amount of water stargrass is a problem the Benton Conservation District has been working on for decades, said Marcella Appel, district manager.
At first, the district noticed this new grass building up. Then, they realized it was native. The district didn’t want to eradicate it, just get it under control, Appel said.
“ We began working 20 years ago on just (hand) pulling this grass out, and we saw returns,” she said. “Then, it became, ‘OK, how can we start to scale up?'”
The district asked Washington state lawmakers for funds to buy a harvester, which looks like an aquatic backhoe with a claw attached to the front. But even with the harvester, progress has been slow in controlling the stargrass.
“It takes a long time to move through that. Sometimes you're fighting the current, sometimes the current's fighting you,” said Thomas Sexton, the conservation director at the Benton Conservation District.
So, the district decided it still needed something that could pull out even more water stargrass.
However, there are challenges: different harvesters work better under different conditions. River depth, bed type, water conditions and grass thickness can impact the harvester’s effectiveness.
There’s also a limited amount of time to do this work. The water stargrass is pulled up when salmon aren’t trying to migrate.
This year, the state Department of Fish and Wildlife and the Yakama Nation are piloting a spider excavator. It’s a big machine with four independently movable legs — and a rake on the front.
“ To basically rake up the star grass, pull (it) up out of the water, float it downstream to where we have a long reach excavator on the shore that can grab it and pull it out and let it dry on the shore,” Maikis said.
The stargrass will be composted, although Maikis said they’re looking into other options in the future. The spider excavator is expected to continue working through the end of September.
So far this year, in about six days of work, the new spider tool pulled up around 10 acres of water stargrass over about one river mile.
Eventually, Zacavish said, the group hopes to get the river in better condition so water stargrass isn’t so out of control. He’s thinking they could experiment with ideas like increasing the water turbidity, which would make it harder for water stargrass to grow. It’d have the added benefit of camouflaging young salmon.
“In a Goldilocks world, I think in 10 years we (would) have a legitimate hold on water star grass. And we wouldn't have to be doing as much manual harvest at that point,” he said.
Plans are already underway for next year.
