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. Flag colors are based on E. coli and cyanobacteria (blue-green algae) levels; blue flags indicate suitable boating conditions and red flags indicate potential health risks.
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. Cyanobacteria monitoring is conducted every 1-2 weeks.
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CRWA's water quality models are predicting blue flags for all boathouses.
In accordance with the MA Department of Public Health (DPH) cyanobacteria (blue-green algae) advisory posted for the Charles River between the Museum of Science and the Mass Ave Bridge, 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. DPH will conduct follow-up sampling when the bloom is no longer evident. DPH requires at least two samples, one week apart, to recommend rescinding the advisory.