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.
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, ones that would require minimal water treatment. Historically, ever larger and more distant reservoirs have been secured in central and western Massachusetts to supply both the quantity and the quality of water needed. As a result, MWRA inherited in 1985 a water system whose sources - Wachusett, Quabbin and the Ware River - are the least polluted available and require a minimal level of treatment - disinfection and corrosion control.
PROTECTING BACKUP SUPPLIES