It’s an early September morning. Crisp fall air and fog fill the Gallatin Canyon. About 10 minutes from Big Sky, Department of Environmental Quality scientist Gabby Metzner and her team are eager to get to work.
They walk along Highway 191 in waders, carrying long metal poles, dangling cords and little devices that look like large calculators with screens. After a minute of walking through brush, they arrive on the banks of the Gallatin River. State Water Quality Scientist Joe Vanderwall enters the river, poles in hand.
In 2023, the DEQ listed sections of the Gallatin as impaired due to recurring algal blooms. The blooms choke out fish and degrade water quality. Vanderwall, Metzner and other colleagues are working to uncover what’s been causing them with a six-year study.
The health of the Gallatin is at the heart of ongoing tension among locals. Everyone agrees the algal blooms are bad and the river is unhealthy. But, exactly how unhealthy is it? And what’s the cause? Environmental groups argue the region’s push for development should slow until the state determines those answers.
The catalyst for this work began in 2018. That was the start of years of consistent algal blooms which blanketed the river in a layer of thick, green, stringy algae.
This is different from “harmful” algal blooms, which are toxic if ingested.
So, the DEQ assessed the river in 2022, but didn’t find what it was expecting. Agency scientists say their samples didn’t show high levels of the things that typically cause algal blooms. The only thing they could be sure about was that algae was impairing the river. So in 2023, the study kicked off in an effort to uncover why.
But Metzger says they ran into another complication this year.
"We haven't been seeing the extensive filamentous, like, long filamentous algae blooms, like what spurred the listing. So we're trying to figure out why is that happening? Is it a multitude of other factors that are also coming into play leading to that excessive algae growth?"
Now scientists are looking at a variety of factors like the river’s speed, its acidity and how much oxygen is in the water. They’re also assessing nutrient levels, and sampling algae and insects. With the help of the nonprofit Gallatin River Task Force, they’re sampling tributaries too.
They’re looking for what’s called nonpoint source pollution. That means harmful chemicals, heavy metals or excessive nutrients leaching into surface waters indirectly.
Algae naturally grows in water bodies. But nutrient pollution from things like fertilizers, erosion, or human waste can cause rapid algal growth and lead to blooms.
This work will help determine how much of those nutrients, like nitrogen and phosphorus, the river can take while still maintaining a high water quality. The study’s results will help set regulations for development that impacts the river.
Locals covet the Gallatin. It’s got world-class fly fishing, rafting and contributes to the unique natural character of the canyon that winds into Yellowstone National Park. More and more people are moving or visiting the area each year. And more people means new development and new septic system waste that could impact the Gallatin.
The nearby resort community Big Sky is growing. U.S. Census data show a 176% population increase between 2010 and 2020.
Johnny O’Connor is the executive director for Big Sky County Sewer and Water.
"On average, our population served here is about 3,500 … So when you add the annual visitation to that, we probably serve on average anywhere from 7- 10,000 a day," he says.
He’s sitting in a conference room at their office in town. The walls are dotted with maps and old photographs of the community.
Big Sky recently began a major expansion of their wastewater treatment to accommodate the growth. Phase One built a larger, technologically advanced treatment facility. For Phase Two – O'Connor gestures to a map and points toward the main corridor of the canyon. There are little blue squares outlining subdivisions and schools.
"All those independent little septic systems that are down there that, you know, have drain fields and stuff, and don't treat to as high of a standard as what we treat to," he says."
O’Connor says their new facility can treat wastewater to higher standards. The treated wastewater is then reused to irrigate the golf course and make snow.
Environmental groups have sued over a variety of issues stemming from treated wastewater use. Sometimes those lawsuits are directed at Big Sky Sewer and Water, others at resorts or golf courses. Some have won out or reached settlements, others flopped.
Environmental non-profit Upper Missouri River Waterkeeper says septic systems are a major culprit when it comes to nutrient pollution. But Executive Director Guy Alsentzer says the onus is on the state to create policies that do not pit development and environmental health against each other:
"We are talking more about 'how do we increase development'," he says. "And it becomes a game of development at any cost, instead of saying development doesn't have to be a race to the bottom for water quality."
He says the wastewater systems and pollution have been managed poorly for years, and it’s made worse by policies loosening state water quality regulations.
He’s in the middle of a lawsuit against the state over those policies. Alsentzer says the state’s push to ease up on regulations for developers is jeopardizing the future of Montana’s rivers.
"The idea of having a science-based set of rules over where and how we develop, isn't a bad thing. And it's certainly not red tape. It's about protecting your drinking water. It's about protecting your wildlife. It's protecting your neighbor and taking responsibility as a sector for how and where we grow."
There’s a shared desire to protect the Gallatin despite disagreements over how. That’s exemplified by groups like the Gallatin River Task Force. They’re a nonprofit that’s collected data in the Upper Gallatin watershed for 25 years. They’re also partnering with the DEQ on this study.
That task force’s Chief Science Officer Kristin Gardiner lives in Big Sky and has led the group for almost two decades.
"I also think it is important that people understand that everyone plays a role," she says. "Not only the larger entities like the water and sewer districts and the bigger developers, but also, like, individual homeowners. In order, I think, to have an impact, like, we're all going to have to be making some sacrifices in the way that we use water."
Gardiner agrees that state water policy must meet the needs of a healthy Gallatin River. But she says this study is a key step in definitively determining what exactly causes these algal blooms and what steps the community can take to prevent them.
"It's just front of mind for everyone here," Gardiner says. "They understand the value of the river. They recreate on the river, their businesses depend on the river. It's a really integral part of our community."
The study should be complete by 2029. The state says it will use the results to inform local development regulations and to help create a plan to protect the Gallatin.
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