Green Lake Reservoir Report
Last Updated: December 20, 2025
Green Lake, a private hydroelectric dam located in Ellsworth, Maine, is a historic structure completed in 1911.
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Summary
With a dam height of 7.5 feet and a storage capacity of 107,000 acre-feet, this masonry dam serves multiple purposes including fire protection, stock pond, fish and wildlife habitat, recreation, and water supply. The dam sits on Reeds Brook and has a surface area of 2,989 acres, with a drainage area of 58 square miles.
Managed by the Federal Energy Regulatory Commission, Green Lake's spillway type is uncontrolled with a width of 80 feet. The dam is considered to have low hazard potential and a moderate risk rating. An emergency action plan was last revised in 2010, with inspection frequency set at every 3 years. The structure, although not currently assessed for condition, continues to be a significant feature in the region's water resource and climate management.
Overall, Green Lake stands as a testament to the intersection of human ingenuity and environmental stewardship, providing essential services while maintaining a balance with nature. Its rich history, diverse functions, and regulatory oversight make it a fascinating subject for water resource and climate enthusiasts seeking to understand the complex dynamics of dam infrastructure in the context of sustainable development and environmental protection.
Year Completed |
1911 |
Dam Length |
273 |
Dam Height |
7.5 |
River Or Stream |
Reeds Brook |
Primary Dam Type |
Masonry |
Surface Area |
2989 |
Drainage Area |
58 |
Nid Storage |
107000 |
Outlet Gates |
Slide (sluice gate) - 2 |
Hazard Potential |
Low |
Foundations |
Rock |
Nid Height |
8 |
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.
Green Lake