Charles River Water Quality Notification Program

Testing the Waters

From July through October, the Charles River Watershed Association notifies the public of water quality conditions in the Charles River Lower Basin, from Watertown to Boston Harbor.  Using a system of color coded flags, CRWA lets recreational river users know when the river is safe for boating or when a public health threat may be present due to bacterial contamination or blue-green algae (a.k.a. cyanobacteria).

The presence of E. coli bacteria in water suggests contamination by sewage, which in turn could mean that disease-causing bacteria or viruses are present.  High bacteria concentrations are typically observed after heavy rainfall when storm drains and sewer system overflows flush pollutants into the river.

CRWA uses a mathematical model to estimate the probability of the river exceeding the State secondary contact recreation (boating) standard for bacteria.  The State boating standard for E.coli bacteria is 630 colony forming units per 100 milliliters of water (cfu/100 mL).  The model, originally created by CRWA and Tufts University, was recently updated by CRWA. It uses recent rainfall and river conditions to predict water quality violations.  In addition, CRWA collects river samples weekly, which are analyzed for E.coli contamination to verify model predictions. 

Health risks due to blue-green algae blooms are estimated by CRWA based on weekly sampling and communication with public health officials.  Blue-green algae concentrations in the Charles River Lower Basin are far less variable than bacteria concentrations. High levels of blue-green algae can secrete a toxin which can cause skin irritations and other health problems; for more information, please visit our blue-green algae page.

Water quality conditions are communicated through the use of three color-coded flags:

	A blue flag is flown when it is estimated that the likelihood of bacteria exceeding theboating standard is less than 50% and there is no blue-green algae bloom present.
	A yellow flag is hoisted when health risks are possible but data is inconclusive to predict risks with certainty.
	A red flag is hoisted when the probability of the river exceeding boating standards is equal to or greater than 50% or a health risk is present due to a confirmed blue-green algae bloom.  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 potential health risks.

River users can be notified of the daily flag color by observing flags flown at our nine partner boating centers, a daily e-mail update, CRWA’s website, or by calling (781) 788-0007 ext. 301.

Background

If you would like further information about CRWA's methodology for predicting bacteria concentrations, read the article "Predicting Fecal Coliform Bacteria Levels in the Charles River" published in the Journal of the American Water Resources Association; or contact Julie Wood at (781)788-0007 x225.

For The Gulf of Maine Times Autumn 2002 article about the public notification program, click here.    

Supporters of the Charles River Water Quality Notification Program

Funders and In-Kind Donations: Monetary support is provided by Boston Water and Sewer Commission and CRWA members. Community Rowing, Inc. generously provides a motorboat for collection of river samples.

Partners Include:  United States Geological Survey,  Access Sport America, Charles River Canoe & Kayak, Charles River Yacht Club,  Community Rowing Inc., Henderson Boathouse (Northeastern University), Newton Yacht Club, Riverside Boat Club, Union Boat Club, Weld Boathouse (Harvard University).