Windsor Lake/Reservoir closed Positive Test Results for BlueGreen Algae

Town of Windsor Closes Windsor Lake Reservoir,

Sites Positive Test Results for Blue-Green Algae

Windsor, CO – On Tuesday, July 23, the Town of Windsor closed Windsor Lake Reservoir to town provided activities until further notice. A precautionary water sample taken from the lake Thursday, July 18 tested positive for cyanobacteria also known as blue-green algae.

Staff have closed and roped off the swim beach and locked up the dog beach. The following activities are prohibited during this time: swimming, bathing and no pets are allowed.

Rentals and concessions will not be available during this time. Annual permitted motorized and non-motorized boaters are allowed on the lake at this time to assist in agitating the water. However, water activities such as tubing and water skiing are not allowed. Non-motorized boaters may use their permits at their own risk.

“Out of an abundance of caution last week we issued a precautionary health advisory. Given today’s positive test, we have closed the lake for usage. A new sample has been sent to the state laboratory today and we will continue to test weekly until the bacteria clears up,” states Director of Parks, Recreation & Culture Eric Lucas.

What is Harmful Algae?

Blue-Green Algae which are not really an algae, they are a type of bacteria, and are common in lakes throughout Colorado. The algae multiply rapidly—and are impacted by a combination of unusually sustained hot weather, stagnant water and stormwater runoff that includes nutrient pollution from fertilizers—to form blooms and scums.

What Contributes to Blue-Green Algae Growth?

Polluted storm-water runoff can have adverse effects on plants, fish, animals and people. Too much nitrogen, potassium and phosphorus in the water is known as nutrient pollution and can cause algae to grow faster than ecosystems can handle. Significant increases in algae harm water quality, food resources, and decrease the oxygen aquatic life. Add sustained hot temperatures and conditions for this type of algae to thrive.

While visitors are advised to use the water at their own risk, they can still enjoy the trail, volleyball net, catch and release fishing, the playground, Boardwalk Park Museum and the park in general. For more information about events happening in Windsor, visit

For water results and more information visit

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