The Quabbin Reservoir, the larger of the Massachusetts Water Resources Authority's two sources, stood at 82.1% of capacity on June 30, 2026. A year earlier, on June 30, 2025, it was at 93.0%, a fall of 10.9 percentage points.
A long run above 93%
The drop stands out against MWRA's earlier quarterly reports. Quabbin volume was 94.5% on June 30, 2018, 99.5% on March 31, 2019 and 94.1% on June 30, 2021. MWRA's fourth-quarter FY2026 report attributes it to a continuing multi-year drought that kept the Quabbin below its normal operating range, though the system remained substantially above MWRA's Drought Warning stage.
Plenty of headroom on paper
The system's safe yield is about 300 mgd under present operating rules. MWRA's 2026 Official Statement puts five-year average withdrawals at 203 mgd, about 100 mgd below that level, and its fourth-quarter FY2026 indicators put five-year average demand at less than 200 mgd. Total storage capacity is about 490 billion gallons: 412 billion at the Quabbin and 65 billion at the Wachusett. MWRA projects that supplies will be sufficient through at least 2060.
Expansion, one town at a time
That headroom has drawn interest from towns outside the system. On November 3, 2026, according to a WBUR report, MWRA withdrew a 20 mgd regional interbasin transfer request after pushback from local communities and lawmakers. It now plans community-specific filings. North Sherborn, Natick, Wayland and Weymouth/South Weymouth Naval Air Station are among the communities still in state review for (partial) MWRA water supply, and none has yet joined the 53 communities MWRA supplies with water.
How the reservoirs, the regional institutions and the treatment and sewer network fit together, and what the 2027 decisions on overflows, tunnels and permits mean for the system, is set out in the full report. The full report, Water Systems Overview: Massachusetts Water Resources Authority, is available for USD 499. For a free overview, read the Massachusetts Water Resources Authority Utility Snapshot.