Is Clear Fork Reservoir safe to swim?

As of July 22, 2026, Clear Fork Reservoir in Morrow County, Ohio is clear to swim. Satellite imagery detected no blue-green algae bloom as of July 18, 2026. Rainfall over the past week totaled 1.4 in, which can wash bacteria and nutrients into the water.

How this read is built

Clear Fork Reservoir is a reservoir in Morrow County, Ohio covering about 1.5 sq mi, the 22nd-largest of the 41 lakes SwimZone monitors in Ohio. 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, Clear Fork Reservoir has reached blue-green algae advisory levels in 5 of them, most recently in September 2025. This is a lake that blooms most summers. Its highest recorded reading was 1,272,047 cells/mL in September 2024.

Is it safe to swim in Clear Fork Reservoir right now?

Clear Fork 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 Clear Fork Reservoir have blue-green algae (cyanobacteria)?

No blue-green algae bloom is detectable at Clear Fork 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 Clear Fork Reservoir?

No bloom is detected at Clear Fork 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 Clear Fork Reservoir have blue-green algae blooms?

Over 7 summers of satellite monitoring since 2020, Clear Fork Reservoir has reached blue-green algae advisory levels in 5 of them, most recently in September 2025. This is a lake that blooms most summers. Its highest recorded reading was 1,272,047 cells/mL in September 2024.

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

Today, 33 Ohio waters are above a safe-contact threshold and 32 more warrant caution, out of 101 monitored waters SwimZone tracks in the state.

How is Clear Fork 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 Clear Fork Reservoir, and a recent-rainfall overlay, all refreshed daily. It was last updated July 22, 2026.