Massabesic Lake Dam Reservoir Report
Last Updated: December 16, 2025
Massabesic Lake Dam, located in Manchester, New Hampshire, serves as a vital structure for water supply purposes.
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Summary
Completed in 1873, this concrete dam stands at a height of 27 feet with a length of 500 feet, holding a maximum storage capacity of 16,580 acre-feet and a normal storage of 2,694 acre-feet. The dam's primary purpose is to regulate the flow of Cohas Brook and provide water resources for the surrounding area.
Despite its historical significance, Massabesic Lake Dam is classified as having a high hazard potential and poor condition assessment, with the last inspection conducted in August 2020. With a moderate risk rating, the dam is under the regulatory oversight of the New Hampshire Department of Environmental Services Dam Bureau. It is crucial for water resource and climate enthusiasts to monitor the maintenance and management of Massabesic Lake Dam to ensure its continued effectiveness in water supply and to mitigate potential risks associated with its structural integrity.
The dam's location within the Hillsborough County, New Hampshire, highlights its importance in the local water infrastructure. With a spillway width of 90 feet and a drainage area of 47 square miles, Massabesic Lake Dam plays a critical role in managing water resources and protecting the surrounding community from potential flooding events. As efforts continue to assess and address its condition and safety measures, Massabesic Lake Dam remains a focal point for water resource management and climate resilience in the region.
Year Completed |
1873 |
Dam Length |
500 |
Dam Height |
27 |
River Or Stream |
COHAS BROOK |
Primary Dam Type |
Concrete |
Surface Area |
2630 |
Drainage Area |
47 |
Nid Storage |
16580 |
Hazard Potential |
High |
Foundations |
Unlisted/Unknown |
Nid Height |
27 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Dam Data Reference
Condition Assessment
SatisfactoryNo 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
HighDams 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.
Massabesic Lake Dam
Massabesic Lake boat launch