Charles River Basin Flagging Program

Testing the Waters

From July through October, the Charles River Watershed Association forecasts daily water quality conditions at four sites in the Charles River Basin.  The water quality models estimate the probability of the river sites exceeding the State secondary contact recreation (boating) standard for fecal coliform bacteria using recent rainfall conditions and results of water quality testing.  The State boating standard for fecal coliform bacteria is 1,000 colony forming units per 100 milliliters (cfu/100 mL); for e.coli bacteria, the State boating standard is 630 cfm/100 mL.  Historical bacteria data from this flagging program, and rainfall data collected by the United States Geological Survey, were used by CRWA and Tufts University to create the models.  

A blue flag is posted when it is estimated that the probability of bacteria exceeding the boating standard is less than 50%.  A red flag is hoisted when the probability of the river exceeding boating standards is equal to or greater than 50%. A yellow flag is hoisted when probability is uncertain, or if there are other factors (such as blue-green algae) potentially impacting boater safety. The presence of fecal bacteria in water suggests contamination by sewage or feces, which in turn could mean that disease-causing bacteria or viruses are present.  Most red flag days occur after heavy rainfall when storm drains and sewer system overflows flush pollutants into the river. CRWA research shows that the Basin does not meet state boating standards over 13% of the time after a heavy rain.

While it is always a good idea to wash after being on the river, it is particularly important on red flag days. Some boaters choose to stay off the river on red flag days because of elevated bacterial levels.

In addition, CRWA will collect river samples once a week, analyze them for fecal contamination, and present the results on our website.   

If you would like further information about CRWA's methodology for predicting bacteria, read the article "Predicting Fecal Coliform Bacteria Levels in the Charles River" published in the Journal of the American Water Resources Association; or contact David Kaplan at 781-788-0007 x224.

For The Gulf of Maine Times Autumn 2002 article, click here.   

Supporters of the Charles River Flagging Program

Partner Includes:  United States Geological Survey

Volunteers from: Access Sport America, Charles River Canoe & Kayak, Charles River Yacht Club, Community Boating, Community Rowing Inc., Henderson Boathouse (Northeastern University), Newton Yacht Club, Riverside Boat Club, Union Boat Club, Weld Boathouse (Harvard University).  (Click on participating program name for their website.)

Funders and In-Kind Donations: Monetary support is provided by the U.S. Environmental Protection Agency and Boston Water and Sewer Commission. Community Rowing, Inc. provides a motorboat for collection of river samples.