Tracking the Concentration of E. coli in the Lower Charles River

May 14, 2008

Based on hydrodynamics and die-off kinetics, a mathematical model of the lower Charles River has reproduced the patterns of E. coli in the water. The results, which were published in the April issue of The Journal of the American Water Resources Association, are likely to impact the creation, location, and management of the region's beaches.

Using spatial and temporal surveys at different times, intervals, and positions along the river, Ferdi Hellweger of Northeastern University and his team had discovered an increased concentration of E. coli after a period of little rainfall. To make sense of more than 750 samples, the team used mathematics to develop a mathematical model that takes into account variables associated with upstream and downstream flows, winds, and sewer overflow from the river's major tributaries, the Muddy River and the Stony Brook.

“Our analysis suggests that the Stony Brook and Muddy River are the predominant sources of E. coli in the lower Charles River,” said Hellweger. Moreover, he said, "It is important to determine where the bacteria go and their concentration at different times and locations.”

One unexpected finding was the effect of the New Charles River Dam, which allows the Charles River to flow into the Boston Harbor. When the dam is closed, the Charles River becomes a static lake or reservoir and the concentration of E. coli increases.

“While the primary focus of the Dam is to control flooding and navigation, I think that taking water quality issues into account could help reduce the public health risk to present boaters and future beachgoers in the Charles,” said Hellweger.

Source: Northeastern University (April 24)