Voice of the River

A River in Bloom

If you’ve spent time along the Gallatin in the past few summers, you’ve likely noticed bright-green algae covering rocks from shoreline to shoreline late in the summer as you’re wading to your favorite fishing hole. Like us, you probably have questions.

Is this natural? If not, what’s causing it? Is it bad for river health and our wild trout? How can it be prevented?

To answer these questions and more, the Task Force has partnered with the Montana Department of Environmental Quality on a multi-year study to determine the primary drivers of the algae blooms and what we must do to stop them. Three years into our research, here’s what we know.

What’s the Cause?
Algae growth is driven by several factors, including phosphorus and nitrogen levels, water
temperature, hardness, pH, velocity, sunlight, and water clarity. On the upper Gallatin, this growth is natural, but the scale of the growth in recent years is unprecedented.

What Changed?
It’s likely that increased nutrients from human activity throughout the upper watershed, plus a variety of changing environmental factors are leading to the excess growth. Climate change has resulted in drier conditions, more sunny days, and warmer air temperatures, all factors that increase the likelihood of a bloom.

What’s the Solution?
In addition to human influence, conditions are changing in the upper Gallatin. Global warming is impacting everything from the winter snowpack to summer air quality, and these factors contribute to algae growth. However, all is not lost.

Improving wastewater management is crucial. Wastewater contains low levels of phosphorus and nitrogen, two nutrients contributing to algae growth. The good news is that the new upgraded treatment plant in Big Sky will further reduce nutrient levels by 99%.

For the 60% of residents who are not connected to the Big Sky Water and Sewer District, regular septic maintenance goes a long way to keeping the river clean. I you can’t remember the last time you cleaned your system, it has been too long.

Additionally, improving the conditions along our streambanks and wetlands will help filter harmful pollutants and keep them from entering our creeks and rivers. Wetlands and riparian vegetation naturally filter contaminants, using the nutrients as fuel.

As you can see, it will take a multi-pronged approach to prevent future blooms.


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