September 27, 2023

A cool, wet spring that extended into June has kept the river flowing steadily through Steamboat Springs for a busy Fourth of July and kickoff to summer. Now that summer is in full swing and flows are rapidly dropping, you may start to shift your water recreation from the river to local reservoirs.

As things start to heat up across the state, algal blooms in reservoirs are always a concern. Blue-green algae or cyanobacteria, which blooms in many reservoirs across the Western U.S. starting in June and lasting through September, can reach toxic levels that could be harmful for humans or pets swimming in or consuming the water. Luckily, we have had very minimal closures for reservoir recreation in Northwest Colorado to date.

In summer 2021, Steamboat Lake was temporarily closed to recreation due to increased toxicity levels from blue-green algae. This brief closure raised awareness of algal toxins and sparked concern among local water users. While blue-green algae is present and may be visible in popular local reservoirs, including Stagecoach Reservoir and Steamboat Lake, many species of cyanobacteria are harmless and the production of toxins remains difficult to predict.  

At Stagecoach Reservoir, Colorado Parks and Wildlife conducts weekly testing of water samples from high-use areas around the marina and swim beach. The Upper Yampa Water Conservancy District (UYWCD) also contracts for additional testing for three months in the summer/fall each year. Since testing at Stagecoach began in 2015, none have resulted in “hazard levels” of toxins, which imposes recreational closures. In recent years, there have been no positive test results for toxicity at Stagecoach Reservoir.

Despite a history of relatively low-risk algal blooms in the area, it is important to note that testing cannot occur at all locations across a reservoir each day. Keeping in mind that toxin production from blue-green algae is difficult to predict in both timing and location, it is also important to be aware when recreating on reservoirs.

Here’s what to know:

  • Swim at your own risk. Unknown hazards exist.
  • Avoid areas of scum whether swimming, wading or boating.
  • Do not drink or allow pets to drink reservoir water.
  • Clean and rinse fish well and discard guts in a trash receptacle
  • Call your doctor or veterinarian if you or your animals have sudden or unexplained sickness or signs of poisoning.

There are still many unknowns surrounding the increased presence of blue-green algae in our reservoirs, including the exact causes. However, UYWCD, along with other local and regional organizations, such as the Upper Yampa Watershed Group and Colorado State University, are working to identify causes and best management practices that could help slow or reduce future algal blooms.

If you have questions regarding the study of cyanobacteria in Stagecoach Reservoir, feel free to contact UYWCD at 970-871-1035.

Holly Kirkpatrick is the public information and external affairs manager for the Upper Yampa Water Conservancy District.

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