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Boston Harbor and Massachusetts Bay
Massachusetts Water Resources Authority

The Charles River


Pollution sources to the lower Charles include upstream community wastewater treatment plants, contaminated stormwater runoff, leaking septic systems, and combined sewer overflow.

In the Charles, most fecal coliform bacteria counts do not exceed the state standard of 200 colonies per 100 milliliters. The area between the Watertown dam and the Arsenal Mall (upstream of any CSO discharges) is the most consistently contaminated section surveyed; and the Charles River Basin, the important recreational area between Cambridge and Boston, had the best bacterial water quality.

Download Charles River data below

Charles River sampling map
See larger map with sampling locations

See all Harbor & river sampling locations


Download Water Quality Data


*For samples collected between June and October of each of the last five full calendar years.



Boston Harbor's Tributary Rivers