Nutrient Pollution on Big Hole River

04/18/2025

Nutrient Pollution on Big Hole River

Monitoring Montana Waters (MMW) provides scientific, technical, and financial support to citizen-led watershed monitoring groups. MMW has provided assistance with water monitoring efforts on the Big Hole River since 2020. The Big Hole River valley encompasses 2,800-square miles of free-flowing, blue-ribbon trout streams, several mountain ranges, and many plant and animal species-of-concern, including the last remaining population of stream-dwelling Arctic grayling found in the Lower 48 United States. The Big Hole is a tributary of the Jefferson River, and it is affected by nutrient pollution, warming temperatures, development, noxious weeds, wildfires, and socioeconomic change.

The Big Hole River Foundation (BHRF) is a science-based organization that works to protect the Big Hole River watershed through water quality monitoring, education, outreach, and advocacy on behalf of its unique culture, fisheries, and wildlife. The primary focus of the BHRF is conducting a long-term water quality monitoring program on the Big Hole River. The BHRF collects data from April to October at 7 mainstem sites and 3 primary tributaries over 150-miles, from Twin Bridges up to the headwaters. The BHRF is the only MMW funded group that has also built an aquatic insect monitoring program to complement their work on water quality. Their effort has resulted in the collection of the most comprehensive aquatic macroinvertebrate dataset on the river to date. Samples are collected at 6 sites, with 4 replicates each, in late September each year. Over five years of water quality data collection, the Big Hole River Foundation has found consistently high levels of nitrogen and phosphorus at multiple sites on the Big Hole.

Trained volunteers serve a crucial role by monitoring water quality in Montana, helping to protect the water quality of our rivers, streams, lakes, and wetlands. Volunteer monitoring efforts help develop comprehensive data sets from which longer-term water quality trends can be discerned. If sampling reveals a significant water quality problem, then baseline data can be used to justify the implementation of more intensive watershed studies, and it can set the stage for formal water quality assessments to take place. In February 2025, Upper Missouri Waterkeeper and the Big Hole River Foundation filed a 32-page petition urging the Montana Department of Environmental Quality to designate the Big Hole River as impaired for nutrient pollution. Excess nutrients in a river system can lead to algae blooms which can lower dissolved oxygen levels and harm fish along with some of the macroinvertebrates that they eat. The petitioners would like DEQ to acknowledge that portions of the Big Hole are exceeding established water quality thresholds and designate the waterway as impaired for nutrient pollution. To read more about the Big Hole River petition to DEQ, check out the articles linked below.