Photo: Rachel Bevins

With 587 miles of shoreline and numerous public beaches on Lake Champlain, and hundreds of swimming holes on rivers in the Basin, there are many ways to cool off in the summer months. For most of the swimming season, beaches in most places on the Lake are safe and open to the public.

While Lake Champlain and its tributaries provide a fine way to cool off on a hot day, swimmers should be aware of water quality and safety considerations before jumping in.

Health Concerns

When a public beach is closed for health concerns, it is usually a result of elevated levels of coliform bacteria, which are an indicator of disease-causing pathogens, or the presence of cyanobacteria (also known as blue-green algae).


High levels of E. coli bacteria in the water is a common cause of beach closings along Lake Champlain. E. coli is a specific species of fecal coliform bacteria. Coliform bacteria are usually harmless and are naturally present in all animals, including humans. E. coli is generally not found growing and reproducing in the environment, so it is considered to be the best indicator of fecal pollution and the possible presence of pathogens. It comes from animal waste, including that of humans, pets, livestock, birds, and wildlife. Dog droppings are one of the leading causes of E. coli pollution. Each gram of dog waste has over 20,000,000 E. coli colonies in it.

Elevated coliform levels typically occur following rainstorms that wash sediment, pollutants, and bacteria into the Lake. Experts advise waiting 24 hours after a heavy rainfall before entering a water body to reduce the risks associated with exposure to unsafe levels of coliform bacteria or high river flows.


Cyanobacteria blooms may produce harmful toxins that can cause gastrointestinal problems, skin irritation, and other symptoms when ingested. It is difficult to determine if a bloom contains toxins, which is why monitoring and an early warning system is critical.

Beach Testing and Closures

Beach Closures for Pathogens

In the summer months, water at many public beaches is tested for fecal coliform and/or E. coli. Swimmers at private beaches and other popular swimming areas that are not tested should use caution after heavy rainfalls.

It can take up to two days for sample analyses to be completed, so the worst of conditions often pass before results are available. Swimmers should avoid areas where streams enter the Lake for 24 hours after intense rainstorms. If the water looks or smells suspicious, it is best to stay out.

In New York and Vermont, the health protective level of E. coli bacteria in recreational water is 235 colony-forming units (CFUs) per 100 milliliters of swimming water for a single sample. For Québec, this limit is 200 CFUs per 100 ml. The New York Department of Health also as regulations for fecal coliform at beaches. The fecal coliform density from a series of five or more samples in any 30-day period shall not exceed a logarithmic mean of 200 CFUs per 100 ml. When any sample exceeds 1,000 colonies per 100 ml, consideration will be given to closing the beach. The presence of any fecal coliform in drinking water is cause for concern and requires immediate action.

Testing and Closure Alerts and Information

Water quality at many beaches and swimming areas around Lake Champlain is tested regularly during the summer months.

Beach Closures for Cyanobacteria

Lake users should practice common sense when dealing with cyanobacteria blooms and be aware that conditions change rapidly, with new blooms forming in just hours. Do not allow your pets to eat clumps of algae that have washed up on the beach. To be safe, don’t let your children play in clumps of algae or drink untreated lake water while swimming or playing in the water. Lake-shore residents with drinking water intake pipes that might pump in blue-green algae should be cautious. No one should drink untreated lake water. Anyone becoming ill after exposure to an algae bloom should seek medical attention.

Cyanobacteria Alerts and Advisories

For questions about cyanobacteria health concerns or to report a bloom:

  • New York: State Dept. of Health, harmfulalgae@health.ny.gov. web →
  • Vermont: State Dept. of Health. web →
  • Québec: Régie régionale de la santé et des services sociaux de la Montérégie (RRSSSM) (Montérégie Public Health Department) (450) 928-6777. web →
  • Québec: Algues bleu-vert (QC MELCC) (514) 644-4545 (région de Montréal). web →

Other Swimming Concerns

Giardia AND Cryptosporidiosis

Giardia and cryptosporidiosis are gastrointestinal illnesses caused by parasites. Drinking untreated water and accidentally ingesting water while swimming are common causes of infection. The greatest concern is the drinking of water from private water supplies that are not filtered. Hikers, paddlers, and other outdoor users should always boil, filter, or chemically treat water from unknown sources.

Swimmer’s Itch

Lake users occasionally report swimmers itch (cercarial dermatitis), a skin irritation caused by a free-swimming stage of a fluke (a flatworm). The fluke lives part of its life cycle in snails and completes its life cycle in water birds. When water birds are not present, the fluke may burrow into a human’s skin, causing itching. No major outbreaks have been reported recently.

More on water quality and swimming concerns

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