Note: It is currently not boating season. We do not display flags when it is not boating season. We hope to see you again in the near future!

Flagging Program - Live Water Quality Alerts

About CRWA's Water Quality Models

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 downstream of the CSO discharge point.
  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 bloom 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.

Stay Updated

The best way to keep up with the CRWA flagging updates is to sign up for email alerts. Email communications from the CRWA are the official source for status updates relating to the Charles River.

You can also follow the CRWA Flagging Program on Twitter to get automated updates from this website. Our Twitterr bot posts automatic updates every time the predictive model is run.