BOSTON – April 24, 2008 – It is a common belief that the water quality of the Charles River and other lakes, streams and rivers is at its worst after a large rain­fall because of pol­lu­tants car­ried by runoff. How­ever, a recent study com­pleted by researchers at North­eastern Uni­ver­sity in Boston found high con­cen­tra­tions of E. coli bac­teria in the Charles River after a long period of no rain. Ferdi Hell­weger, Ph.D., Assis­tant Pro­fessor of Civil and Envi­ron­mental Engi­neering and Acting Director of the Center for Urban Envi­ron­mental Studies, both at North­eastern, used high-​​resolution mon­i­toring and mod­eling to under­stand the fate and trans­port of E. coli bac­teria in the lower sec­tion of the Charles River to deter­mine what fac­tors may lead to the increased concentration.

The results, which were pub­lished in the April issue of the Journal of the Amer­ican Water Resources Asso­ci­a­tion, go above and beyond the cur­rent data avail­able about the water quality in the Charles and have the poten­tial to impact the loca­tion of future beaches and their management.

Because cur­rent mon­i­toring pro­grams do not resolve the small-​​scale pat­terns of E. coli, Hell­weger and his team car­ried out a high-​​resolution mon­i­toring pro­gram. Using spa­tial and tem­poral sur­veys at dif­ferent inter­vals and loca­tions, Hell­weger and his team gath­ered 757 sam­ples along tran­sects across and along the river, and over time at a fixed loca­tion. The results indi­cated an increased con­cen­tra­tion of E. coli after a period of little rain­fall. To make sense of these results, they devel­oped a math­e­mat­ical model of the river. The model accounts for var­ious dri­vers, including upstream and down­stream flow, wind, com­bined sewer over­flow (CSO) and non-​​CSO flow from two major trib­u­taries, the Muddy River and the Stony Brook. Based on hydro­dy­namics and die-​​off kinetics, the model repro­duced the gen­eral pat­terns of E. coli in the water over space and time.

Our analysis sug­gests that the Stony Brook and Muddy River are the pre­dom­i­nant sources of E. coli in the lower Charles River,” said Hell­weger, whose interest in urban hydrology drove this research project. “How­ever, it is impor­tant to deter­mine where the bac­teria go and their con­cen­tra­tion at dif­ferent times and locations.”

One sur­prising finding was the effect of the New Charles River Dam, which when open, allows the Charles River to flow down­stream and empty into the Boston Harbor. When it is closed, how­ever, the Charles River acts more like a lake or a reser­voir, cre­ating a static envi­ron­ment. Thus, in addi­tion to rain­fall, the Dam oper­a­tion cycle does affect the level of bac­teria in the Charles River.

Our study results show that water quality in the Charles River is impacted by sev­eral fac­tors, including the New Charles River Dam,” added Hell­weger. “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 public health risk to present boaters and future beach­goers in the Charles,” added Hellweger.

Their model can be used to pre­dict water quality in the lower Charles River, which can be used to eval­uate var­ious man­age­ment sce­narios and assess public health risk to swim­mers at dif­ferent times and locations.

In a 2002 study, 25% of sur­veyed beaches had at least one advi­sory or area closed, mostly due to unsafe levels of cer­tain forms of bac­teria. Expo­sure to unsafe levels of bac­te­rial can some­times result in recre­ational water ill­nesses (RWI), causing diar­rhea, res­pi­ra­tory, skin, ear and eye infections.

Water pol­lu­tion con­tinues to be a public health threat, and because the Summer is quickly approaching, there will be a height­ened interest in pro­tecting people who spend time in the water. “My goal is to help make the Charles River a place where people can swim safely,” said Hellweger.

About North­eastern

Founded in 1898, North­eastern Uni­ver­sity is a pri­vate research uni­ver­sity located in the heart of Boston. North­eastern is a leader in inter­dis­ci­pli­nary research, urban engage­ment, and the inte­gra­tion of class­room learning with real-​​world expe­ri­ence. The university’s dis­tinc­tive coop­er­a­tive edu­ca­tion pro­gram, where stu­dents alter­nate semes­ters of full-​​time study with semes­ters of paid work in fields rel­e­vant to their pro­fes­sional inter­ests and major, is one of the largest and most inno­v­a­tive in the world. The Uni­ver­sity offers a com­pre­hen­sive range of under­grad­uate and grad­uate pro­grams leading to degrees through the doc­torate in six under­grad­uate col­leges, eight grad­uate schools, and two part-​​time divi­sions. For more infor­ma­tion, please visit www​.north​eastern​.edu