Tennanah Lake Dam Reservoir Report

Last Updated: December 6, 2025

Tennanah Lake Dam, located in Sullivan County, New York, stands as a testament to the importance of water resource management and climate resilience.


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Summary

Built in 1914, this concrete dam serves primarily for recreational purposes, offering a serene backdrop for visitors to Tennanah Lake. With a height of 17 feet and a length of 41 feet, the dam plays a crucial role in regulating the flow of Trout Brook and maintaining the surrounding ecosystem.

Despite its age, Tennanah Lake Dam remains in good condition, with regular inspections conducted by the New York State Department of Environmental Conservation. With a significant hazard potential and a high-risk assessment rating, the dam is closely monitored to ensure its structural integrity and the safety of nearby residents and recreational users. Although the spillway type is listed as "None," the dam is equipped with outlet gates for controlled water release in case of emergency.

As climate change continues to impact water resources and infrastructure, the importance of maintaining and upgrading dams like Tennanah Lake Dam becomes increasingly evident. With proper risk management measures in place and a dedication to ongoing maintenance and inspection, this dam serves as a vital component in safeguarding the surrounding community and natural environment against potential water-related hazards.

Year Completed

1914

Dam Length

41

Dam Height

17

River Or Stream

TROUT BROOK

Primary Dam Type

Concrete

Hazard Potential

Significant

Nid Height

17
       
Seasonal Comparison

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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.