In its 16th season, our Water Quality Notification Program has continued to keep the public informed of the Charles River’s conditions with the assistance of 10 local boathouse partners in the Lower Basin. Between June 27th and October 19th, our interns collected 140 water samples and took water temperature and depth readings from four sites along the river: the North Beacon Street Bridge, the Larz Anderson Bridge, the Boston University Bridge, and the Longfellow Bridge.
CRWA intern Blair Frantz boating to the Longfellow Bridge sampling site with the Boston University Bridge behind her.
These samples are used to verify our bacteria prediction model, which alerts partnered boathouses along the river to fly a blue flag when there are no predicted public health risks and a red flag when boating isn’t safe. Our bacteria prediction model uses weather data gathered from our own weather station located on a small island near the Community Boating facility in Boston. It records environmental data (rainfall, wind speed, air and water temperature) every 10 minutes. This data is then automatically run through four separate complex models that predict E. coli bacteria concentrations hourly.
Unfortunately, this year’s samples indicated that the water quality has worsened from previous years. Compared to last year’s 99.14%, only 89% of this year’s samples met the Single Sample Standard for Secondary Contact. Massachusetts’ water quality standard for boating states that if E. coli bacteria levels exceed 1,260 colony-forming units per 100 milliliters, the water is not safe for boating.
Like previous years, the river’s water quality was impacted by stormwater runoff associated with wet weather events. This rainfall picks up contaminants as it drains to the river untreated, causing elevated levels of E. coli bacteria. While 2016’s wet weather events didn’t meet standards 8.33% of the time, 29.27% of this year’s wet-weather samples didn’t meet standards.
Overall, the best water quality was found at the Longfellow Bridge sampling site, with no samples exceeding the single sample boating standard. The Boston University Bridge site only exceeded the single sample boating standard in 4 samples, while the Larz Anderson Bridge site exceeded the standard twice. The poorest water quality was found at the North Beacon Street site, where 9 samples exceeded the single sample boating standard. These findings are consistent with previous years, where we have found that water downstream is of better quality than water upstream.