Oswego Lake Dam Reservoir Report
Last Updated: December 13, 2025
Oswego Lake Dam is a private-owned structure located in Lake Oswego, Oregon, and serves multiple purposes including hydroelectric power generation and recreation.
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Summary
Completed in 1921, this concrete dam stands at 32 feet tall and has a structural height of 34 feet, with a storage capacity of 9,800 acre-feet. Situated on the Tualatin River offstream, it plays a significant role in managing water resources in the region.
With a maximum discharge capacity of 1,400 cubic feet per second, Oswego Lake Dam is a crucial component of the local watershed, providing flood control and water supply for various uses. Despite its age, the dam's hazard potential is rated as significant, highlighting the importance of regular inspections and maintenance to ensure its safety and effectiveness. The dam's emergency action plan status and risk management measures are currently not rated, underscoring the need for ongoing monitoring and preparedness in the face of changing climate conditions.
As a key feature in the water resource infrastructure of Clackamas County, Oregon, Oswego Lake Dam represents a blend of historical significance and modern functionality. Its role in hydroelectric power generation and recreational activities underscores the importance of balancing human needs with environmental stewardship in managing water resources. With a focus on safety, risk assessment, and emergency preparedness, the dam continues to play a vital role in the region's water management efforts amidst the challenges posed by a changing climate.
Year Completed |
1921 |
Dam Length |
120 |
Dam Height |
32 |
River Or Stream |
TUALATIN RIVER (OFFSTREAM) |
Primary Dam Type |
Concrete |
Surface Area |
433 |
Hydraulic Height |
26 |
Drainage Area |
6 |
Nid Storage |
9800 |
Structural Height |
34 |
Outlet Gates |
Slide (sluice gate) |
Hazard Potential |
Significant |
Nid Height |
34 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Tryon Creek Blw Nettle Creek
|
11cfs |
Johnson Creek At Milwaukie
|
116cfs |
Tualatin River At West Linn
|
4260cfs |
Fanno Creek At Durham
|
36cfs |
Clackamas River Near Oregon City
|
6250cfs |
Fanno Creek At 56th Ave
|
3cfs |
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.
Oswego Lake Dam
Willamette Greenway Lake Oswego