Lock 4 - Stillwater Reservoir Report
Last Updated: December 15, 2025
Lock 4 - Stillwater, also known as Stillwater Dam, is a concrete gravity dam located in Stillwater, New York.
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Summary
Built in 1955, this dam serves the primary purpose of hydroelectric power generation on the Hudson River. With a height of 5 feet and a length of 820 feet, Lock 4 has a storage capacity of 3,150 acre-feet and a maximum discharge of 200,000 cubic feet per second. It is regulated by the Federal Energy Regulatory Commission and is inspected regularly to ensure its safety and functionality.
The dam features an uncontrolled spillway with a width matching its length, and is equipped with four slide (sluice gate) outlet gates. The hazard potential of Lock 4 is deemed significant, while its risk assessment rates it as moderate. While the condition assessment is not available, emergency action preparedness measures have been put in place, with the last revision of the Emergency Action Plan occurring in January 2021. Lock 4 - Stillwater continues to play a critical role in water resource management and climate resilience efforts in the region, showcasing the importance of sustainable hydroelectric infrastructure for a greener future.
Enthusiasts and experts in water resources and climate will find Lock 4 - Stillwater to be an intriguing subject of study, with its unique design, operational features, and role in renewable energy production. As a key player in the hydroelectric sector, this dam exemplifies the intersection of engineering, environmental stewardship, and regulatory oversight. With its rich history and ongoing maintenance efforts, Lock 4 stands as a testament to the vital importance of responsible water resource management in the face of evolving climate challenges.
Year Completed |
1955 |
Dam Length |
820 |
Dam Height |
5 |
River Or Stream |
Hudson River |
Primary Dam Type |
Concrete |
Surface Area |
1500 |
Drainage Area |
3745 |
Nid Storage |
3150 |
Outlet Gates |
Slide (sluice gate) - 4 |
Hazard Potential |
Significant |
Foundations |
Rock |
Nid Height |
5 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Hudson R Above Lock 1 Nr Waterford Ny
|
4840cfs |
Hudson River At Lock 1 Near Waterford Ny
|
4430cfs |
Mohawk River At Cohoes Ny
|
2440cfs |
Hudson River At Green Island Ny
|
3650cfs |
Hoosic River Near Eagle Bridge Ny
|
413cfs |
Glowegee Creek At West Milton Ny
|
15cfs |
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.
Lock 4 - Stillwater
Hudson River Road 951, City of Mechanicville