Reservoirs & Watersheds

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MWRA and the Department of Conservation and Recreation keep a daily watch on reservoir levels at Quabbin (412 billion gallon capacity) and Wachusett (65 billion).

While Wachusett levels are kept relatively fixed, Quabbin levels fluctuate with precipitation and watershed runoff.

Ware River stream flows are also watched daily to determine if seasonal transfers to Quabbin during high-flow periods are possible. To gauge current system status, water supply planners have identified six reservoir status conditions that allow for normal monthly fluctuation.

The Quabbin/Wachusett system is so large that it can withstand short- and medium-length droughts and dry periods without a significant impact on its operating levels.

Drought Status

The Quabbbin Reservoir is currently in the "normal" stage.

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Safe Yield

MWRA's source reservoirs, the Quabbin and Wachusett, can be counted on to safely provide about 300 million gallons per day of water even during periods of extended drought. This amount is called the "safe yield."

For a 20-year period from 1969 to 1988, the customers of MWRA (and its predecessor MDC) routinely drew more than the safe yield.

The chart Water System Demand 1980-2019 (PNG) demonstrates this historical trend. Fortunately, precipitation was great enough throughout these years to avoid a major water supply crisis. To address this problem, MWRA launched an aggressive water conservation program in 1986. By 1989, withdrawals had been brought below the safe yield, where they have remained ever since.

This reduction in average water use was achieved through:

• Vigorous leak detection and repair efforts on MWRA and community pipes
• Retrofitting 370,000 homes with low-flow plumbing devices
• A Water Management Program for area businesses, municipal buildings and nonprofit organizations
• Extensive public information and school education programs
• A change in the state plumbing code requiring new toilets to be 1.6 gallon per flush
• Meter improvements that helped track and analyze community water use
• New water-efficient technology that has created reductions in residential use
• Water pipeline replacement and rehabilitation projects throughout the MWRA and community systems

Managing Demand

Information on water use, system yield, watershed precipitation and levels of the Quabbin Reservoir are tracked on a daily and monthly basis. Based on a detailed analysis of major factors affecting water demand, MWRA projects that system demand will remain well below 300 million gallons per day.

A review of demand and supply conditions (PDF), presented to the MWRA Board of Directors in January 2016, provides more detail on long term trends.