Willow Brook Dam Reservoir Report

Last Updated: December 6, 2025

Willow Brook Dam, also known as Orange Rockland Lakes, is a public utility dam located in Bull Mine, Orange County, New York.


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Summary

Completed in 1924, this earth dam stands at a height of 20 feet and spans 550 feet in length, with a primary purpose of recreation. The dam has a storage capacity of 995 acre-feet and a surface area of 76 acres, providing a tranquil setting for outdoor enthusiasts to enjoy the surrounding natural beauty.

With a drainage area of 1.53 square miles and a maximum discharge rate of 935 cubic feet per second, Willow Brook Dam is regulated by the New York State Department of Environmental Conservation. Despite its high hazard potential and poor condition assessment, the dam is inspected biennially to ensure public safety. Additionally, the dam's spillway, which is uncontrolled and 24 feet wide, serves as a vital feature for managing water levels during periods of high flow.

For water resource and climate enthusiasts, Willow Brook Dam offers a fascinating glimpse into the intersection of human infrastructure and natural landscapes. As a recreation-focused structure in a picturesque setting, the dam serves as both a practical water management tool and a beloved outdoor destination for locals and visitors alike.

Year Completed

1924

Dam Length

550

Dam Height

20

River Or Stream

TR-MERRIEWOLD LAKE

Primary Dam Type

Earth

Surface Area

76

Drainage Area

1.53

Nid Storage

995

Hazard Potential

High

Nid Height

20
       
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.