SwimZone

Reservoir · Geauga County · OH

Is East Branch Reservoir safe to swim?

Advisory

Blue-green algae is above the safe-contact threshold.

Updated July 22, 2026 · EPA CyAN satellite

Recent rain
0.5 in
Water type
Reservoir
Last updated
Jul 22
Bacteria
E. coli, fecal
Not monitored
Tested
Not monitored

No bacteria advisory or sampling for this water.

Blue-green algae
cyanobacteria
Advisory
Tested
855,112
cells/mL
Advisory over
100,000
cells/mL

Cyanobacteria 855,112 cells/mL (satellite, 7-day max), imaged 2026-07-21.

Sampled Jul 21 · EPA CyAN satellite

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There's an advisory on East Branch Reservoir right now.

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What's in the water at East Branch Reservoir right now

As of July 22, 2026, East Branch Reservoir in Geauga County, Ohio is not recommended for swimming. Satellite imagery measured 855,112 cells/mL of blue-green algae on July 21, 2026, above the 100,000 cells/mL advisory threshold. Rainfall over the past week totaled 0.5 in, which can wash bacteria and nutrients into the water.

How this read is built

Blue-green algae at East Branch Reservoir

East Branch Reservoir is a reservoir in Geauga County, Ohio covering about 0.6 sq mi, the 34th-largest of the 41 lakes SwimZone monitors in Ohio. Satellite imagery measured 855,112 cells/mL of blue-green algae on July 21, 2026, above the 100,000 cells/mL advisory threshold.

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.

Bloom history at East Branch Reservoir

From EPA CyAN's satellite archive

2020: peak 763,384 cells/mL — above the 100,000 advisory level202021: peak 1,642,037 cells/mL — above the 100,000 advisory level212022: peak 721,279 cells/mL — above the 100,000 advisory level222024: peak 2,307,932 cells/mL — above the 100,000 advisory level242025: peak 2,119,644 cells/mL — above the 100,000 advisory level2526Advisory100k cells/mL

Each bar is that summer's peak satellite reading (log scale). The red cap is the part above the advisory level.

Over 6 summers of satellite monitoring since 2020, East Branch 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 2,307,932 cells/mL in September 2024.

When to swim at East Branch Reservoir

It is currently peak season for blue-green algae, when warm, calm water lets blooms form fastest. This lake has bloomed in most monitored summers (5 of 6), historically peaking around September. Early summer, before the water fully warms, has generally been the safer window here; check the current read before you go either way.

Frequently asked: swimming in East Branch Reservoir

Is it safe to swim in East Branch Reservoir right now?
East Branch Reservoir is not recommended for swimming today. Satellite imagery measured 855,112 cells/mL of blue-green algae on July 21, 2026, above the 100,000 cells/mL advisory threshold. Conditions can change quickly with wind, heat, and rain, so check the posted signs and look at the water before you get in.
Does East Branch Reservoir have blue-green algae (cyanobacteria)?
Yes. Satellite monitoring measured 855,112 cells/mL of blue-green algae (cyanobacteria) at East Branch Reservoir on July 21, 2026, above the 100,000 cells/mL advisory level. Avoid swimming and keep children and pets out of the water.
Can dogs swim in East Branch Reservoir?
No. Blue-green algae at East Branch Reservoir is above the safe-contact threshold (855,112 cells/mL on July 21, 2026). Cyanobacteria toxins can be rapidly fatal to dogs, which swallow it while swimming and lick it from their fur. Keep dogs out of the water and away from any scum along the shore.
How often does East Branch Reservoir have blue-green algae blooms?
Over 6 summers of satellite monitoring since 2020, East Branch 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 2,307,932 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 East Branch 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 East Branch Reservoir, and a recent-rainfall overlay, all refreshed daily. It was last updated July 22, 2026.

Before you swim: the basics

Swim spots near East Branch Reservoir

All Ohio →

Of the 6 monitored waters nearest East Branch Reservoir, 5 are flagged today.

WaterDistanceTodayAlgae readSampled
Akron City ReservoirReservoir · Geauga County11 miAdvisory855,112 cells/mLJul 21
Lake Roaming RockLake · Ashtabula County16 miAdvisory1,072,959 cells/mLJul 19
Fairport HarborBeach · Lake County19 miClear to swimNot monitoredJul 22
Aurora PondPond · Portage County20 miAdvisory1,385,042 cells/mLJul 21
Mosquito Creek LakeLake · Trumbull County20 miAdvisory114,105 cells/mLJul 21
Royal Acres BeachBeach · Cuyahoga County22 miUse cautionNot monitoredJul 22