We can impact algae growth in the following ways:

  • Nutrients: Nitrogen and phosphorous are two essential nutrients for plants and animals that can cause a cascade of negative effects in river ecosystems. The main sources of nitrogen identified by the EPA are agriculture through manure and fertilizer; stormwater, which carries pollution to rivers; wastewater, including treated effluent and septic systems; household sources like fertilizer, pet waste, etc.; and fossil fuels.
  • Temperature: The Montana Climate Assessment predicts the annual average daily temperature may increase by 5.6 to 9.8 degrees F by the end of the century. This will warm local rivers and streams exacerbating algae blooms.
  • Streamflow: Warmer temperatures may affect water supply by causing more precipitation to fall as rain, rather than snow. This could decrease winter snowpack, which feeds waterways throughout the hot, dry summer. Furthermore, our public water supply comes from groundwater, which is highly connected to rivers and streams in our area. As the Big Sky community grows, increased water use will threaten water levels in rivers and streams. Low water levels contribute to warm, stable conditions conducive to algae growth.
  • Light: Streamside plants, like willows, shade waterways. Removing streamside plants during development may encourage algae growth by increasing the amount of light that reaches streams and warming streamwater.
  • Stormwater: Removing vegetation and disturbing the ground during residential and resort development loosens and exposes soil, which is full of nutrients. Then, wind and water carry soil and nutrients downhill to rivers and streams. In addition, the particles suspended in cloudy water absorb more heat.

Learn what you can do to protect local rivers and streams here.