Denley Reservoir Report
Nearby: Rock Island Dam Port Leyden
Last Updated: December 14, 2025
Denley, a hydroelectric dam located in Port Leyden, New York, has been a key player in the region's water resource management since its completion in 1912.
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Summary
Owned privately, Denley is regulated by the NYS DEC and the Federal Energy Regulatory Commission, ensuring that it meets state and federal standards for safety and operation. With a dam height of 29 feet and a length of 350 feet, Denley has a storage capacity of 350 acre-feet and covers a surface area of 41 acres.
Situated on the Black River in Lewis County, Denley plays a crucial role in both flood control and electricity generation for the surrounding area. The dam's spillway, with a width of 284 feet, helps manage the flow of water during peak discharge events. Despite its age, Denley has a low hazard potential and a moderate risk assessment rating, indicating that it is well-maintained and poses minimal risk to the community. Emergency preparedness measures, including an Emergency Action Plan last revised in December 2020, ensure that any potential risks are effectively managed.
Overall, Denley stands as a testament to the enduring importance of hydroelectric infrastructure in the face of climate change and evolving water resource management practices. As a historic and functional piece of the region's hydrology, Denley continues to serve as a reliable source of renewable energy and a critical component of the local water management system. Its role in balancing environmental concerns with energy production highlights the complex interplay between water resources and climate resilience in the modern era.
Year Completed |
1912 |
Dam Length |
350 |
Dam Height |
29 |
River Or Stream |
Black River |
Primary Dam Type |
Concrete |
Surface Area |
41 |
Drainage Area |
398 |
Nid Storage |
350 |
Hazard Potential |
Low |
Foundations |
Rock |
Nid Height |
29 |
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.
Denley
Bottom (Fowlersville to Lyons Falls)