Is Lake Buchanan safe to swim?

As of July 20, 2026, Lake Buchanan in Llano County, Texas is clear to swim. Satellite imagery detected no blue-green algae bloom as of July 19, 2026. Rainfall over the past week totaled 1.7 in, which can wash bacteria and nutrients into the water.

How this read is built

Lake Buchanan is a lake in Llano County, Texas covering about 34.4 sq mi, the 12th-largest of the 218 lakes SwimZone monitors in Texas. Satellite imagery detected no blue-green algae bloom as of July 19, 2026. Larger, warmer waters like this can hold a bloom for weeks once nutrients and calm weather line up.

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, Lake Buchanan has reached blue-green algae advisory levels in 3 of them, most recently in August 2025. Its highest recorded reading was 527,938 cells/mL in May 2024.

Is it safe to swim in Lake Buchanan right now?

Lake Buchanan 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 Lake Buchanan have blue-green algae (cyanobacteria)?

No blue-green algae bloom is detectable at Lake Buchanan 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 Lake Buchanan?

No bloom is detected at Lake Buchanan 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 Lake Buchanan have blue-green algae blooms?

Over 7 summers of satellite monitoring since 2020, Lake Buchanan has reached blue-green algae advisory levels in 3 of them, most recently in August 2025. Its highest recorded reading was 527,938 cells/mL in May 2024.

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

Today, 78 Texas waters are above a safe-contact threshold and 85 more warrant caution, out of 399 monitored waters SwimZone tracks in the state.

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