Is Branched Oak Lake safe to swim?

As of July 20, 2026, Branched Oak Lake in Lancaster County, Nebraska is not recommended for swimming. Satellite imagery measured 1,385,042 cells/mL of blue-green algae on July 19, 2026, above the 100,000 cells/mL advisory threshold. Rainfall over the past week totaled 0.0 in, which can wash bacteria and nutrients into the water.

How this read is built

Branched Oak Lake is a lake in Lancaster County, Nebraska covering about 2.7 sq mi, the 7th-largest of the 75 lakes SwimZone monitors in Nebraska. Satellite imagery measured 1,385,042 cells/mL of blue-green algae on July 19, 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.

Over 7 summers of satellite monitoring since 2020, Branched Oak Lake has reached blue-green algae advisory levels in 7 of them, most recently in July 2026. This is a lake that blooms most summers. Its highest recorded reading was 1,737,893 cells/mL in August 2023.

Is it safe to swim in Branched Oak Lake right now?

Branched Oak Lake is not recommended for swimming today. Satellite imagery measured 1,385,042 cells/mL of blue-green algae on July 19, 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 Branched Oak Lake have blue-green algae (cyanobacteria)?

Yes. Satellite monitoring measured 1,385,042 cells/mL of blue-green algae (cyanobacteria) at Branched Oak Lake on July 19, 2026, above the 100,000 cells/mL advisory level. Avoid swimming and keep children and pets out of the water.

Can dogs swim in Branched Oak Lake?

No. Blue-green algae at Branched Oak Lake is above the safe-contact threshold (1,385,042 cells/mL on July 19, 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 Branched Oak Lake have blue-green algae blooms?

Over 7 summers of satellite monitoring since 2020, Branched Oak Lake has reached blue-green algae advisory levels in 7 of them, most recently in July 2026. This is a lake that blooms most summers. Its highest recorded reading was 1,737,893 cells/mL in August 2023.

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

Today, 44 Nebraska waters are above a safe-contact threshold and 4 more warrant caution, out of 83 monitored waters SwimZone tracks in the state.

How is Branched Oak Lake'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 Branched Oak Lake, and a recent-rainfall overlay, all refreshed daily. It was last updated July 20, 2026.