MWRA Online image
Water System
Sewer System
Harbor and Bay
School Program
About MWRA
Doing Business with MWRA
Contact MWRA
Source Water Assessment and Protection Program
Massachusetts Water Resources Authority

About Watersheds

A watershed is the total area that drains directly across the land and indirectly through the groundwater, to a particular stream, river, pond or reservoir. Precipitation that falls anywhere in the watershed of a given reservoir or stream will eventually end up in that body of water. We protect watersheds because all activities within them have impacts - some small, some great - on their water quality.


A History of Protected Source Waters

The best way to deliver clean, safe water is to start with high quality source water. Since the 1870s, planners have sought relatively pristine and protected water sources for Metropolitan Boston. Historically, ever larger and more distant reservoirs have been secured in central and western Massachusetts to supply the quantity and the quality of water needed. In 1985, MWRA inherited a water system whose sources: the Wachusett, Quabbin and the Ware River, are the least polluted available, requiring a minimal level of treatment:.

MWRA/Department of Conservation and Recreation Watershed Protection efforts continue this heritage by assuring that the source water quality is as high as it can be.
For more information, go to:

In addition to its source reservoirs, MWRA maintains backup water supplies throughout the metropolitan area. While these waterbodies do not have to meet stringent daily drinking water quality requirements, they are kept on standby status to be used in case of emergency.


Source Water Assessment and Protection Program Report

The Source Water Assessment and Protection Program (SWAP) is a planning tool developed by the Massachusetts Department of Environmental Protection (DEP) with guidance from the U.S. Environmental Protection Agency (EPA) to support local and state efforts to improve water supply protection.

The SWAP employs Geographic Information System (GIS) mapping and other guidance to depict land uses and potential threats to the source water and its watershed. DEP's SWAP for the MWRA system noted that MWRA and MDC's Division of Watershed Management "meet DEP's annual review of "Measures of Success" for implementation of Watershed Protection Plans and disinfection treatment processes.

Further, the SWAP notes that "MWRA and MDC have implemented DEP-approved Watershed Protection Plans to protect source waters since 1991."

Copies of the SWAP report are sent by DEP to the chief elected official in the community (Mayor, Town Manager, etc.), the municipal water system, the local Board of Health and Board of Planning. More information on the SWAP report is also available on DEP's website, or by calling the Department of Environmental Protection at (617) 292-5500.


SWAP Information for MWRA's Partially-Supplied Water Communities

For communities whose water also comes from local supplies, you will have a separate report. Information on this report can also be found on DEP's website, or by calling (617) 292-5500.

If you would like a copy of the SWAP report for the MWRA system mailed to you, please contact Beverly Anderson at (617) 788-4822.

Updated July 19, 2022