Is it safe to swim in
In most areas of Lake Champlain, the water quality is usually very safe for recreational use, including swimming. At certain times of the year, however, harmful algae blooms may develop, causing localized recreational health hazards. Occasionally, following a heavy rainstorm, unhealthy levels of coliform bacteria may be present in the waters near beaches for a few days, which creates localized recreation concerns.
Although most of Lake Champlain is normally safe for swimming, some shallow areas frequently develop unhealthy conditions. In recent years the waters in some areas, particularly in St. Albans Bay and several areas of Missisquoi Bay, have developed conditions that caused the beaches to be closed to swimmers. Of the 35 public beaches on Lake Champlain, 23 were closed two or fewer times between 2012 and 2014. When a public beach is closed for health concerns, it is typically for risk of exposure to coliform bacteria or to toxins produced by harmful algae blooms (Figure 8).
In Lake Champlain, elevated levels of coliform bacteria typically occur after heavy rainstorms, which wash sediment, pollutants, and bacteria into the Lake. Very heavy rainstorms may cause municipal sewers to overflow, sending untreated sewage directly into the Lake. These events are called Combined Sewer Overflows (CSOs). CSOs occur in towns and cities with stormwater systems that are connected to the sewer system. Ideally, a municipality should have two separate systems, one to carry sewage to a wastewater treatment facility and another to handle stormwater independently. Constructing and maintaining separate systems can be very costly, so municipalities often try to find other ways to reduce stormwater flows in their sewer systems, but leave the systems combined. Public beaches along Lake Champlain were closed on more than 30 occasions between 2012 and 2014 as a result of elevated coliform bacteria levels.
Blooms of cyanobacteria, or blue-green algae, sometimes (but not always) produce toxins that are harmful to humans and other animals. Short-term exposure to these toxins can lead to minor skin irritation and stomach issues, and longer-term exposure (for example the ingestion of water that is high in algae toxins) can result in damage to the liver or the central nervous system. Although there are no records of serious human health effects known from algae in Lake Champlain, the risk of exposure makes it prudent to close beaches in areas when and where heavy algae blooms are observed. Public beaches on Lake Champlain closed more than 25 times between 2012 and 2014 as a result of harmful algae blooms.