CRWA's Flagging Program uses a system of color-coded flags to indicate whether or not the river's water quality is safe for boating at eleven boating locations between Watertown and Boston. Blue flags indicate suitable boating conditions and red flags indicate potential health risks.
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In accordance with the MA Department of Public Health (DPH), a cyanobacteria (blue-green algae) advisory has been posted for the Charles River between the Mass Ave Bridge and New Charles River Dam. Red flags are being flown at Charles River Yacht Club, Union Boat Club, Community Boating, and Paddle Boston at Kendall Square. Public health officials recommend that people and pets avoid contact in areas of algae concentration and rinse thoroughly in the event of contact. See current advisories in Massachusetts. CRWA’s water quality models are predicting blue flags for all boathouses, based only on E. coli bacteria predictions.
Last Updated: Monday, September 21, 2020 5:00 PM
Newton Yacht Club
Watertown Yacht Club
Community Rowing, Inc.
Northeastern's Henderson Boathouse
Paddle Boston at Herter Park
Harvard's Weld Boathouse
Riverside Boat Club
Charles River Yacht Club
Union Boat Club
Paddle Boston at Kendall Square
What Do the Flags Mean? Blue flags indicate suitable boating conditions. Red flags indicate potential health risks. Consider avoiding areas where red flags are posted or make sure you wash after boating nearby.
About CRWA's Flag Color Predictions CRWA uses 3 different indicators to determine flag colors at each boathouse. (1) If any Combined Sewer Overflow (CSO) discharges took place in the past 48 hours in the Lower Basin, red flags will be flown at all boathouses. (2) If a cyanobacteria (blue-green algae) bloom is present in the vicinity, red flags will be flown at the affected boathouses for the duration of the bloom. Cyanobacteria monitoring is conducted at least every two weeks while the notification program is active and CRWA coordinates closely with the MA Department of Public Health who recommends blood advisories. (3) If CRWA's water quality models predict E. coli bacteria levels that exceed the State's recreational water quality standards, red flags will be flown at the affected boathouses. CRWA estimates E. coli bacteria levels using models that take into account a variety of environmental factors including rainfall and river flow. CRWA collects water samples weekly to verify the model forecasts.
Today's flag colors are a conservative estimate of water quality conditions. Actual water quality may vary from predictions.
About Cyanobacteria (Blue-Green Algae) Blooms For additional information on cyanobacteria blooms, we encourage you to visit the following websites:
At this time, it is recommended that you avoid contact with the water. People should rinse off with fresh water immediately if they or their pet comes into contact with the water. If you believe you or your pet is experiencing adverse health effects, contact your doctor or veterinarian immediately. Blue-green algae is extremely toxic to pets.