Is Upper Enterprise Reservoir safe to swim?

As of July 20, 2026, Upper Enterprise Reservoir in Washington County, Utah is clear to swim. Satellite imagery detected no blue-green algae bloom as of July 18, 2026. Rainfall over the past week totaled 0.6 in, which can wash bacteria and nutrients into the water.

How this read is built

Upper Enterprise Reservoir is a reservoir in Washington County, Utah covering about 0.6 sq mi, the 40th-largest of the 48 lakes SwimZone monitors in Utah. Satellite imagery detected no blue-green algae bloom as of July 18, 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, Upper Enterprise Reservoir has reached blue-green algae advisory levels in 5 of them, most recently in June 2026. This is a lake that blooms most summers. Its highest recorded reading was 527,938 cells/mL in July 2025.

Is it safe to swim in Upper Enterprise Reservoir right now?

Upper Enterprise Reservoir is clear to swim today. Satellite imagery detected no blue-green algae bloom as of July 18, 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 Upper Enterprise Reservoir have blue-green algae (cyanobacteria)?

No blue-green algae bloom is detectable at Upper Enterprise Reservoir as of July 18, 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 Upper Enterprise Reservoir?

No bloom is detected at Upper Enterprise 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 Upper Enterprise Reservoir have blue-green algae blooms?

Over 7 summers of satellite monitoring since 2020, Upper Enterprise Reservoir has reached blue-green algae advisory levels in 5 of them, most recently in June 2026. This is a lake that blooms most summers. Its highest recorded reading was 527,938 cells/mL in July 2025.

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

Today, 7 Utah waters are above a safe-contact threshold and 0 more warrant caution, out of 53 monitored waters SwimZone tracks in the state.

How is Upper Enterprise 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 Upper Enterprise Reservoir, and a recent-rainfall overlay, all refreshed daily. It was last updated July 20, 2026.