Alder Lake Dam Reservoir Report

Last Updated: December 6, 2025

Alder Lake Dam, located in Turnwood, New York, is a state-owned structure on Alder Creek with a primary purpose of recreation.


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Summary

Completed in 1994, this earth dam stands at a height of 18 feet and has a length of 300 feet, creating a reservoir with a storage capacity of 480 acre-feet. With a normal storage capacity of 397 acre-feet and a surface area of 44 acres, the dam serves as a popular recreational spot for water resource and climate enthusiasts in Ulster County, New York.

Managed by the New York State Department of Environmental Conservation (NYS DEC), Alder Lake Dam is regulated, permitted, inspected, and enforced by state agencies. The dam has a low hazard potential and a moderate risk assessment rating. Its spillway type is uncontrolled with a width of 10 feet, and it has a maximum discharge capacity of 400 cubic feet per second. Although the dam's condition assessment is currently listed as "Not Rated," it remains a vital structure for water resource management and recreational activities in the region.

Despite not being owned or funded by federal agencies, Alder Lake Dam plays a crucial role in water management and recreation in the area. With its picturesque setting and convenient location, the dam provides opportunities for boating, fishing, and other outdoor activities, making it a beloved destination for locals and visitors alike. The dam's presence on Alder Creek adds to the natural beauty of the surrounding landscape and serves as a reminder of the importance of responsible water resource management in the face of changing climate conditions.

Year Completed

1994

Dam Length

300

Dam Height

18

River Or Stream

ALDER CREEK

Primary Dam Type

Earth

Surface Area

44

Drainage Area

2.93

Nid Storage

480

Hazard Potential

Low

Nid Height

18
       
Seasonal Comparison

Weather Forecast

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.