Yellow flags are being flown at the three downstream locations due to a cyanobacteria (a.k.a. blue-green algae) bloom in the Esplanade lagoon and the mainstem of the Charles near these three locations.  Cyanobacteria produce toxins that are potentially harmful to humans and pets.  The Massachusetts Department of Public Health has posted advisories along the Esplande.  For more information on cyanobacteria click here.

 A blue flag indicates safe boating conditions.     

 A yellow flag indicates inconclusive data to predict possible health risks.

 A red flag indicates likely health risks.

Avoid areas where red flags are posted or make sure you wash after boating nearby.  Flag colors are based on bacteria levels and blue-green algae counts.  Today's flag colors are a conservative estimate of water quality conditions.  Actual water quality may vary from predictions.