Blue-green algae prompts swimming closure at Big Soda Lake

JEFFERSON COUNTY, Colo. — Big Soda Lake in Morrison closed for swimming on Thursday after harmful levels of blue-green algae were detected in the water. 

The algae naturally occurs in aquatic ecosystems and can appear rapidly – especially during the summer with hot weather and in slow-moving water bodies, like lakes. Certain varieties of blue-green algae can produce toxins that are linked to illness in humans and animals. 

“The health and safety of our staff and visitors is a top priority at Bear Creek Lake Park,” said Regional Park Supervisor Drew Sprafke. “Working with the state, we have closely monitored the water quality in the last few weeks, first closing down Bear Creek Reservoir in the park due to algae last week and now Big Soda Lake.”

RELATED: Be cautious of potentially harmful blue-green algae this summer

The lake will remain open on-lake approved paddle craft including paddleboards, canoes, kayaks, windsurfing, and rafts but paddlers must have no contact with the water, according to release from the City of Lakewood. 

As a result of degrading water quality and low water levels, park staff does not expect that Big Soda Lake will reopen for swimming this year. Lakewood city officials said the lake typically closes for the season after Labor Day weekend. 

Algae was also the cause for a closure late last month at Cherry Creek State Park's swimming beach. It's the second time the swim area has closed this summer due to an algae bloom, Colorado Parks and Wildlife (CPW) said. The first closure was on July 10.

RELATED: Algae causes closure of swim area at Cherry Creek State Park

According to the Colorado Department of Public Health and Environment (CDPHE), harmful algae blooms often have these characteristics: 

• May look like thick pea soup or spilled paint on the water's surface. 
• Can create a thick mat of foam along the shoreline.
• Usually are green or blue-green, although they can be brown, purple or white. 
• Sometimes are made up of small specks or blobs floating just at or below the water's surface

CDPHE said harmful algae blooms are not:

• Long, stringy bright green grass strands that feel either slimy or cottony.
• Mustard yellow (this probably is pollen).

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