Is Michael J Kirwan Reservoir safe to swim?

As of July 22, 2026, Michael J Kirwan Reservoir in Portage County, Ohio is clear to swim. Satellite imagery detected no blue-green algae bloom as of July 19, 2026. Rainfall over the past week totaled 2.2 in, which can wash bacteria and nutrients into the water.

How this read is built

Michael J Kirwan Reservoir is a reservoir in Portage County, Ohio covering about 4.1 sq mi, the 9th-largest of the 41 lakes SwimZone monitors in Ohio. 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, Michael J Kirwan Reservoir has not reached a blue-green algae advisory level. Conditions can still change quickly, so check the current read before you swim.

It is currently peak season for blue-green algae, when warm, calm water lets blooms form fastest. This water has no recorded advisory-level bloom in its satellite history, which makes it a comparatively steady summer swim spot; conditions still change between samples, so check the current read before you go.

Is it safe to swim in Michael J Kirwan Reservoir right now?

Michael J Kirwan 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 Michael J Kirwan Reservoir have blue-green algae (cyanobacteria)?

No blue-green algae bloom is detectable at Michael J Kirwan 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 Michael J Kirwan Reservoir?

No bloom is detected at Michael J Kirwan 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 Michael J Kirwan Reservoir have blue-green algae blooms?

Over 7 summers of satellite monitoring since 2020, Michael J Kirwan Reservoir has not reached a blue-green algae advisory level. Conditions can still change quickly, so check the current read before you swim.

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 Michael J Kirwan 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 Michael J Kirwan Reservoir, and a recent-rainfall overlay, all refreshed daily. It was last updated July 22, 2026.

• Blue-green algae and dogs→
• What does blue-green algae look like?→
• When is algae season?→