Cabot Spillway Reservoir Report

Last Updated: December 5, 2025

Located in Greenfield, Massachusetts, the Cabot Spillway is a concrete gravity dam completed in 1915 for hydroelectric and recreational purposes.


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Summary

With a height of 35 feet and a length of 168 feet, the dam has a maximum storage capacity of 21,500 acre-feet and serves a drainage area of 7,163 square miles. The spillway, with a controlled type and a width of 120 feet, can discharge up to 16,000 cubic feet per second.

Managed by the Federal Energy Regulatory Commission, the Cabot Spillway has a low hazard potential and a very high risk assessment rating. Despite not being state-regulated, inspected, or permitted, the dam features eight slide gates for outlet control and is associated with six other structures in the area. While its condition assessment is not currently available, the dam's emergency action plan was last revised in 2011, highlighting the importance of preparedness in the face of potential climate-related challenges.

For water resource and climate enthusiasts, the Cabot Spillway presents an intriguing case study of a historic dam in New England with significant hydroelectric capacity. As debates around dam safety and climate resilience continue, the risk management measures and emergency protocols for the Cabot Spillway serve as a reminder of the importance of proactive planning and monitoring in safeguarding critical infrastructure against potential hazards and impacts of a changing climate.

Year Completed

1915

Dam Length

168

Dam Height

35

River Or Stream

Turners Falls Canal

Primary Dam Type

Concrete

Surface Area

2000

Drainage Area

7163

Nid Storage

21500

Outlet Gates

Slide (sluice gate) - 8

Hazard Potential

Low

Foundations

Rock

Nid Height

35
       
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.
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Area Campgrounds