Is Park Reservoir safe to swim?

As of July 20, 2026, Park Reservoir in Sheridan County, Wyoming is clear to swim. Satellite imagery detected no blue-green algae bloom as of July 19, 2026. Rainfall over the past week totaled 0.5 in, which can wash bacteria and nutrients into the water.

How this read is built

Park Reservoir is a reservoir in Sheridan County, Wyoming covering about 0.5 sq mi, the 61st-largest of the 67 lakes SwimZone monitors in Wyoming. Satellite imagery detected no blue-green algae bloom as of July 19, 2026.

Blue-green algae (cyanobacteria) blooms are most common from midsummer into early fall, when the water is warm, calm, and rich in nutrients from runoff. They can produce toxins that make people sick and can be rapidly fatal to dogs, so skip water that looks green, scummy, or like spilled paint, and keep children and pets out of it.

Over 7 summers of satellite monitoring since 2020, Park Reservoir has reached blue-green algae advisory levels in 1 of them, most recently in July 2023. Blooms here have been occasional rather than annual. Its highest recorded reading was 231,901 cells/mL in July 2023.

Is it safe to swim in Park Reservoir right now?

Park Reservoir is clear to swim today. Satellite imagery detected no blue-green algae bloom as of July 19, 2026. Conditions can change quickly with wind, heat, and rain, so check the posted signs and look at the water before you get in.

Does Park Reservoir have blue-green algae (cyanobacteria)?

No blue-green algae bloom is detectable at Park Reservoir as of July 19, 2026 (below the satellite's roughly 10,000 cells/mL detection limit). Cyanobacteria can still appear within hours in warm, calm, nutrient-rich water, so look before you swim.

Can dogs swim in Park Reservoir?

No bloom is detected at Park Reservoir today, but dogs are much more vulnerable to blue-green algae than people, and blooms can form within hours. Always keep dogs away from water that looks green, scummy, or discolored, and rinse them off after swimming.

How often does Park Reservoir have blue-green algae blooms?

Over 7 summers of satellite monitoring since 2020, Park Reservoir has reached blue-green algae advisory levels in 1 of them, most recently in July 2023. Blooms here have been occasional rather than annual. Its highest recorded reading was 231,901 cells/mL in July 2023.

How many Wyoming lakes and beaches are unsafe for swimming today?

Today, 7 Wyoming waters are above a safe-contact threshold and 1 more warrant caution, out of 74 monitored waters SwimZone tracks in the state.

How is Park Reservoir's water quality measured?

SwimZone builds this read from EPA CyAN satellite imagery for blue-green algae, official beach and fecal-bacteria advisories where a program monitors Park Reservoir, and a recent-rainfall overlay, all refreshed daily. It was last updated July 20, 2026.