Lake Housatonic Reservoir Report

Last Updated: December 5, 2025

Lake Housatonic, also known as Derby Dam, is a historic masonry dam located on the Housatonic River in Shelton, Connecticut.


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Summary

Built in 1870, this dam serves multiple purposes including flood risk reduction, hydroelectric power generation, recreation, and water supply. With a height of 25.2 feet and a length of 850 feet, Lake Housatonic has a normal storage capacity of 4400 acre-feet and a surface area of 325 acres.

Managed by a private owner, Lake Housatonic is regulated by the Federal Energy Regulatory Commission (FERC) and does not fall under state jurisdiction. The dam has a high hazard potential and is inspected annually to ensure its structural integrity and safety. Despite its age, the dam continues to play a crucial role in providing clean energy and recreational opportunities for the surrounding community.

Situated in New Haven County, Lake Housatonic offers a picturesque setting for water resource and climate enthusiasts to appreciate the intersection of human engineering with the natural environment. With its uncontrolled spillway and maximum discharge capacity of 160,000 cubic feet per second, this historic dam remains a significant landmark in the region, blending functionality with scenic beauty along the Housatonic River.

Year Completed

1870

Dam Length

850

Dam Height

25.2

River Or Stream

Housatonic River

Primary Dam Type

Masonry

Surface Area

325

Drainage Area

1574

Nid Storage

4400

Hazard Potential

High

Nid Height

25
       
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.