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Boston Harbor and Massachusetts Bay
Massachusetts Water Resources Authority

The Mystic River


Bacterial counts in the Mystic River vary greatly depending on location. Alewife Brook, a tributary, is one of the most contaminated water bodies in the Boston area, due mainly to stormwater. Here, fecal coliform counts routinely fail to meet the state standard. However, bacterial water quality is fairly good downstream, except for a noticeable increase near Medford Square. Water quality improves near the river’s mouth.

Download Mystic River data below

Mystic River sampling map
Larger map with sampling locations

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