Hopkinton Reservoir Report
Last Updated: December 16, 2025
Hopkinton, also known as Contoocook Dam, is a hydroelectric structure located in Merrimack, New Hampshire.
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Summary
Owned by the local government, this concrete dam was completed in 1890 and serves as a key component in harnessing the power of the Contoocook River for energy generation. With a height of 10 feet and a length of 325 feet, the dam boasts a storage capacity of 380 acre-feet and a maximum discharge of 7000 cubic feet per second.
Managed by the Federal Energy Regulatory Commission, Hopkinton Dam has a low hazard potential and is regularly inspected to ensure its structural integrity. The dam's spillway type is uncontrolled, with a width of 270 feet, allowing for the safe release of excess water during periods of high flow. Despite its moderate risk assessment rating, the dam's emergency action plan was last revised in 2006, highlighting the need for updated preparedness measures in the event of a potential hazard.
Water resource and climate enthusiasts will appreciate the role that Hopkinton Dam plays in the local hydroelectric infrastructure, providing renewable energy while also managing water flow along the Contoocook River. With its historical significance dating back over a century, this structure serves as a testament to the innovative engineering techniques of the time and continues to contribute to the sustainable development of the region's water resources.
Year Completed |
1890 |
Dam Length |
325 |
Dam Height |
10 |
River Or Stream |
Contoocook River |
Primary Dam Type |
Concrete |
Surface Area |
110 |
Drainage Area |
437 |
Nid Storage |
380 |
Hazard Potential |
Low |
Nid Height |
10 |
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.
Hopkinton
Depot Lane Hopkinton
Sewall'S Island To Manchester Street Bridge