Boston Harbor, Rivers & Beaches
Boston Harbor is an estuary— a marine ecosystem where fresh water from the rivers enters the ocean. The results of monitoring show how Boston Harbor has steadily become cleaner since the effluent and solids discharges from the Deer Island and Nut Island Treatment Plants were removed. Since 1989, the Massachusetts Water Resources Authority (MWRA) has measured bacteria, algae, water clarity, dissolved oxygen, nutrients, and suspended solids at more than 70 locations in the Harbor and the Charles, Neponset, and Mystic rivers.
The Massachusetts Department of Conservation & Recreation monitors water quality at Wollaston, Carson, Constitution, Tenean and Pleasure Bay beaches. For more information, see the Department of Public Health's Current public beach postings (May-Sep) and/or historical data for all Massachusetts coastal beaches.
Boston Harbor and its Tributary Rivers
Boston Harbor
The 50 square miles encompassing the Boston Harbor estuary include tributary rivers mixing with the salt water of Massachusetts Bay. There are eight main watersheds that drain into Boston Harbor. The Harbor has benefitted from the Boston Harbor Project.
Charles River
The Charles travels 80 miles from Echo Lake in Hopkinton to Boston Harbor. The river's mouth has been dammed since the early 1900s, controlling river flow and flooding. However, the dam prevents tidal flushing, trapping pollutants in the basin.
Mystic River
The Mystic is dammed and flows for 5 miles from the Mystic Lakes in Winchester and Arlington, east through Medford, somerville, and Chelsea to Boston Harbor. These dense residential and industrial areas impact the river due to pollution from development.
Neponset River
The Neponset spans 28 miles from Foxboro to Boston Harbor. Its estuary is the harbor's largest saltmarsh, an important wildlife habitat and natural pollutant filter. The estuary is designated as one of three Areas of Critical Environmental Concern (ACEC).
Current public beach postings (May-Sep) are available from the Massachusetts Department of Public Health.
