Blue flags are being flown at boathouses upstream of the Mass Ave Bridge, as predicted by our water quality forecasting model. A public health notification has been issued and remains in effect for the Charles River downstream of the Mass Ave Bridge. A cyanobacteria (a.k.a. blue-green algae) bloom was identified and confirmed in this area on June 30th. During bloom conditions, people and pets should avoid water with blue-green algae, and any shore areas where algae have washed up. Do not swallow water. Rinse off after contact. The recent flagging conditions are most likely due to the increased rainfall that the Greater Boston Area has experienced over the past several days. For more information visit CRWA’s cyanobacteria webpage or contact MA Department of Public Health at 617-624-5757.
CRWA's Water Quality Notification Program presents the daily flag colors of the river's health, which signify whether or not the river is safe for boating at ten boating locations from Watertown to Boston. Flag colors are based on bacteria levels and blue-green algae counts.
CRWA estimates bacteria levels using a model that takes into account a variety of environmental factors including antecedent rainfall and river flow. CRWA collects river samples for bacteria weekly to verify the model forecast. Blue-green algae monitoring is conducted at least every two weeks. Read more about the development of CRWA's bacteria prediction model.
Indicate suitable boating conditions
Indicate inconclusive data to preclude a possible health risks