Skip to main content

You are here

DEQ: Gallatin River is impaired by algal blooms


By Isabel Hicks Chronicle Staff Writer Jun 21, 2022

The Department of Environmental Quality made a preliminary decision earlier this month to classify the Gallatin River as “impaired” by algal blooms.

The decision comes after several conservation groups banded together to petition the state for impairment classification. The groups involved are the Upper Missouri Waterkeeper, Gallatin River Task Force, Montana Trout Unlimited, Greater Yellowstone Coalition, and American Rivers.

DEQ’s decision is based on an evaluation of all available data collected in the past ten years, including water quality monitoring performed by DEQ and the Gallatin River Task Force, that demonstrate the extent of algal blooms in the Gallatin.

Guy Alsentzer, executive director for Upper Missouri Waterkeeper, said they began to track algal blooms in the Gallatin in 2018. The algal blooms are severe, and concentrated in the middle segment of the river. Some sections have algae lining the bottom and sides of the river for several miles, he said.

Patches of algal blooms are normal, but the amount of algae in the Gallatin is cause for concern, Alsentzer said.

The explosion of algal blooms is caused by a nutrient imbalance in the river. According to Alsentzer, nutrient pollution from manmade sources like wastewater and fertilizer runoff is causing the imbalance.

A river with too many algal blooms is an “abnormal, severe pollution event,” Alsentzer said. Algae can degrade water quality, harm fisheries, and impact anyone who relies on a clean, healthy river for anything from recreation to irrigation.

The first step of addressing the issue is designating the river as impaired, a decision that was made by DEQ on June 14.

Next is a public comment period. DEQ will hold a public meeting on July 14 in Big Sky to discuss the assessment. People can join either in-person or remotely.

After the public comment period, DEQ will need to submit a formal impairment designation to the EPA. If the EPA approves, that sets the stage for DEQ to come up with a cleanup plan.

The cleanup plan would involve determining which sources are contributing the most to nutrient imbalance in the river. Then, DEQ would work with the most prominent sources to treat water in order to reduce the amount of manmade nutrients that end up in the river.

A DEQ press release from Monday said 25% of water samples exceeded thresholds for algae. Excess algae is often caused by a surplus of nitrogen and phosphorus in the river, but the samples didn’t show nitrogen or phosphorus exceeding their thresholds.

“DEQ will need to determine what is causing excess algae in the Gallatin River and then develop … standards, as needed, to reduce the pollutants causing excess growth,” the press release said.

According to Alsentzer, no one has ever petitioned a state to classify a river as impaired from algal blooms.

“The Gallatin is very sensitive to any nutrient inputs above what is naturally occurring,” Alsentzer said. “Let’s use science to protect the thing we all need.”

Alsentzer encouraged people to submit public comment in support of the impairment designation. All kinds of people rely on the river and have a stake in keeping it healthy and clean, he said.

Ballot initiative I-191, which would have asked voters to decide on increased protections for the river, did not get enough signatures in support to make the November ballot. The deadline for signature gathering was last Friday.

The initiative would have asked voters to support an “outstanding resource water” designation for parts of the Gallatin and Madison rivers. The designation would have limited some recreational and commercial use of the river in favor of environmental protection.

John Meyer, an environmental lawyer who spearheaded the initiative, said he will continue to work on the issue for the 2024 election.

Meyer also acknowledged the extensive algal blooms in the Gallatin.

“I think we can stop algal blooms if we stop violations of the Clean Water Act,” Meyer said.