A Zebra Mussel Invasion Threatens Irrigated Agriculture in the Northwest | Civil Eats

A Zebra Mussel Invasion Threatens Irrigated Agriculture in the Northwest

Zebra Mussels on a pole. (Photo courtesy of the Washington Department of Fish and Wildlife

John Rylaarsdam’s farm, near the towns of Quincy and George in Eastern Washington, receives about seven inches of rainfall each year. But he says it takes 25 to 30 inches of water to produce the alfalfa and timothy he grows. To fill the gap in supply, Rylaarsdam and other farmers rely on artificial irrigation to water their crops.

That’s why tiny mollusks that originated in Eastern Europe worry him so much.

The Columbia River Basin, which stretches from Wyoming to Washington and into Canada, is the last great river system in the U.S. to remain free of invasive zebra and quagga mussels. With small, thumbnail-sized shells, these mollusks reproduce quickly, growing on top of each other and clogging critical water and power infrastructure.

For years, zebra and quagga mussels have caused expensive problems for farmers across the country, and each year, they inch closer to the Columbia River Basin, with high-profile scares along the way. Now, they have the potential to create serious agricultural impacts in the Northwest, costing hundreds of millions of dollars annually, by some estimates.

“It’s such a horrifying thing to think about,” said Rylaarsdam, who also serves a director of the Quincy-Columbia Basin Irrigation District. “It doesn’t keep me awake, but I am very concerned.”

It’s impossible to predict the specific impacts of an infestation on individual farmers, but experts warn that it would likely be widespread. The region’s agricultural water system would be vulnerable if these mussels were to become established, said John O’Callaghan, who spent decades working on the Columbia Basin Project with the Bureau of Reclamation. He now works with the South Columbia Basin Irrigation District, which serves more than 200,000 acres with hundreds of miles of canal and pipe.

“You can’t introduce a coating of shells to those facilities and have them function correctly,” O’Callaghan said. “In the water delivery context, it reduces the capacity of canals and gate structures and pipelines. That would reduce the number of acres we’re able to serve, because we would not be able to get adequate water flow through the facilities.”

But it’s not a water supply issue, O’Callaghan said. “It wouldn’t necessarily reduce the amount of water available at the river, but it would reduce our ability to deliver the water that we have historically delivered to meet demand. It’s a pretty binary thing. You either you have the water, or you don’t.”

Climate change and declining snowpack further complicate the prospects for farmers. Even though the Northwest is notoriously wet, rainfall drops off in the agricultural regions east of the Cascades. That makes irrigation critical infrastructure, especially for growers of iconic (and thirsty) crops like apples, other tree fruit, alfalfa, and corn, O’Callaghan said.

“If you can only get less water, you’re going to irrigate less land or you’re going to have reduced yields off your various crops,” O’Callaghan said.

Washington hasn’t had to deal with an infestation yet, and it hopes to keep it that way as long as possible. Still, state and federal officials have outlined the cost elsewhere. “Rural communities dependent on irrigated agriculture experience higher maintenance costs on farms from mussels clogging pumps, expensive pivot and drip irrigation systems, and canals,” the Department of Interior said in a statement in 2020.

Quagga mussels have colonized Lake Mead and the Colorado River, which supply water for several western states. A 2019 Montana Invasive Species Council study noted that customers in California’s Coachella Valley Water District have been assessed mitigation surcharges of “$2.78 per acre-foot but has been as high as $5.75 per acre-foot,” warning of similar impacts in the state. Using those numbers, that study estimated costs to farmers in Montana using sprinkler irrigation systems between $29-$60 million annually.

The Coachella Valley Water District wrote in 2021 that mussels had not colonized Lake Cahuilla or the Coachella Canal, and it adds chlorine to Colorado River water entering the canal to prevent mussels.

Officials know from other regions that mussels can work into virtually any part of a water system.

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“It could be everywhere,” said Heidi McMaster, Northwest regional quagga mussel coordinator for the Bureau of Reclamation. “We have so many water projects and people within the region that rely on water distribution from Reclamation dams. That includes the irrigation districts that receive those waters, and the impacts would be top down. If it impacts the dams, then it impacts the irrigation districts, then it impacts the end users, the farmers.”

To what degree a mussel invasion would hit those farmers individually, she can’t say. Contracts negotiated by irrigation districts differ, with some passing on different costs to customers. Producers could also see their energy costs rise, she said, as hydropower dams face costly de-fouling measures.

An Unexpected Vector

For years, Western states have operated boat check stations to halt and clean watercraft with hitchhiking zebra mussels. But in 2021, officials realized with horror that mussels had made it into Washington state in a way no one expected: moss balls used in home aquariums.

That February, a pet store employee in Seattle noticed and reported a zebra mussel in a moss ball. After an investigation, federal officials realized stores in 21 states had received these moss balls, renewing fears of introduction into new waterways. The public was asked to destroy the moss balls to prevent contamination.

“Around the West, we spend tens to hundreds of millions of dollars annually to inspect watercraft,” said Justin Bush, executive director of the Washington Invasive Species Council. “And one day, we woke up and realized that the perimeter defense of the Western United States had been breached significantly, to a point that we don’t even understand today. We do not know how many infested moss balls still remain in aquariums today. It is alarming.”

The scare did have one positive impact: bringing local attention to the issue.

“Amazingly enough, that happened right smack dab in the middle of the legislative session,” said Captain Eric Anderson, who runs the Washington Department of Fish and Wildlife’s aquatic invasive species program. “It raised the awareness and . . . basically doubled what we got in state funds.”

Now he’s looking at an annual budget of about $750,000, with additional matching funds from federal programs. It’s allowed him to increase prevention efforts, including expanding the hours of the permanent boat check stations, which now run 365 days a year.

The agency is also opening several seasonal stations at other entry points across the state, with the goal of securing funding for more. A second mussel-sniffing dog, Fin, will join the existing dog, Puddles, on the detection force this summer.

“If zebra and quagga mussels get into the Columbia, it would be an epic disaster,” Anderson said. He estimates a $500 million annual cost to manage an infestation in Washington alone, which is exponentially more than the cost of current prevention efforts. Separately, the state invasive species council estimates a minimum $100 million a year to keep water running, which is why officials call this a pivotal moment for prevention.

In 2021, state Fish and Wildlife check stations caught 39 infected boats out of 55,000 examined. That tiny positivity rate—just .07 percent—gives Anderson hope. Still, they’ve already caught a handful this year, and the summer boating season hasn’t yet begun in earnest.

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“We’re trying to do everything within our power to keep them out,” he said.

What Comes Next

Justin Bush, of the Washington Invasive Species Council, believes an infestation in the Columbia River basin is fairly inevitable. Still, every year it’s delayed translates into money saved by governments and farmers.

“It’s probably a matter of when and not if, just based on the number of vectors and water bodies in the states that are already infested,” he said. “But the longer we can prevent this problem, the more likely that we’re going to come up with some new solutions through science, potentially gene editing. We’ll have better chemicals, for example, and mitigation systems. I have no doubt that technology will catch up at some point. But it would be a lot easier and a lot more cost efficient to fully prevent it in the first place.”

With that in mind, Rylaarsdam is bracing for a future where increased water rates from mussel mitigation cut into the profits of family farms like his.

“I’m sure big operations are going to have resources maybe to deal with it,” he said “but for smaller operations, it would be—I hate words like catastrophic—but I can’t imagine.”

It’s why he hopes for more investment in efforts to keep these mussels out and for people to understand the potential impact in Eastern Washington. An ounce of prevention, as the saying goes.

“This place is a garden,” Rylaarsdam said. “But it’s like any other garden: If you take the water away, you don’t have anything.”

Michael Crowe is a journalist based in Seattle, Washington. His work focuses on science, the environment, and climate change. Read more >

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  1. Shayne
    Can these mussels be collected and ground up for fertilizer?

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