Quabbin Spillway Reservoir Report

Last Updated: December 9, 2025

Quabbin Spillway, located in Ware, Massachusetts, is a concrete dam completed in 1938 with a primary purpose of water supply.


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Summary

This structure spans 405 feet in length and reaches a height of 10 feet, serving as a crucial component of the water resource infrastructure in the region. The dam has a storage capacity of 1,810,000 acre-feet, with a surface area of 25,216 acres and a drainage area of 187 acres, making it a significant contributor to the water supply system in Hampshire County.

Managed by the Department of Conservation and Recreation, Quabbin Spillway is regulated by the state of Massachusetts and undergoes regular inspections to ensure its satisfactory condition and low hazard potential. Although classified as a moderate risk structure, the spillway remains a reliable asset for water management and flood control on the Swift River. With its uncontrolled spillway type and moderate risk assessment, the Quabbin Spillway stands as a testament to the state's commitment to water resource management and climate resilience in the face of changing environmental conditions.

Year Completed

1938

Dam Length

405

Dam Height

10

River Or Stream

SWIFT RIVER

Primary Dam Type

Concrete

Surface Area

25216

Hydraulic Height

10

Drainage Area

187

Nid Storage

1810000

Hazard Potential

Low

Foundations

Unlisted/Unknown

Nid Height

10
       
Seasonal Comparison

Weather Forecast

Dam Data Reference

Condition Assessment

Satisfactory
No existing or potential dam safety deficiencies are recognized. Acceptable performance is expected under all loading conditions (static, hydrologic, seismic) in accordance with the minimum applicable state or federal regulatory criteria or tolerable risk guidelines.
Fair
No existing dam safety deficiencies are recognized for normal operating conditions. Rare or extreme hydrologic and/or seismic events may result in a dam safety deficiency. Risk may be in the range to take further action. Note: Rare or extreme event is defined by the regulatory agency based on their minimum
Poor A dam safety deficiency is recognized for normal operating conditions which may realistically occur. Remedial action is necessary. POOR may also be used when uncertainties exist as to critical analysis parameters which identify a potential dam safety deficiency. Investigations and studies are necessary.
Unsatisfactory
A dam safety deficiency is recognized that requires immediate or emergency remedial action for problem resolution.
Not Rated
The dam has not been inspected, is not under state or federal jurisdiction, or has been inspected but, for whatever reason, has not been rated.
Not Available
Dams for which the condition assessment is restricted to approved government users.

Hazard Potential Classification

High
Dams assigned the high hazard potential classification are those where failure or mis-operation will probably cause loss of human life.
Significant
Dams assigned the significant hazard potential classification are those dams where failure or mis-operation results in no probable loss of human life but can cause economic loss, environment damage, disruption of lifeline facilities, or impact other concerns. Significant hazard potential classification dams are often located in predominantly rural or agricultural areas but could be in areas with population and significant infrastructure.
Low
Dams assigned the low hazard potential classification are those where failure or mis-operation results in no probable loss of human life and low economic and/or environmental losses. Losses are principally limited to the owner's property.
Undetermined
Dams for which a downstream hazard potential has not been designated or is not provided.
Not Available
Dams for which the downstream hazard potential is restricted to approved government users.