Cottage Grove Lake Nr Cottage Grove Reservoir Report

Last Updated: December 7, 2025

Cottage Grove Lake is a reservoir located in Lane County, Oregon.


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Summary

The lake was created in 1942 by the construction of Cottage Grove Dam on the Coast Fork Willamette River. The dam's primary purpose is to provide flood control and hydroelectric power to the region. The lake's hydrology is influenced by its location in the Coast Range, which receives significant amounts of precipitation. The primary surface flow provider is the Coast Fork Willamette River, while snowpack also contributes to the lake's water supply. The lake is used for a variety of recreational activities, including boating, fishing, and swimming, and it also provides irrigation water for nearby agricultural operations. The area surrounding the lake is home to a variety of wildlife, including bald eagles and otters.

Reservoir Details

Lake Or Reservoir Water Surface Elevation Above Ngvd 1929, Ft 24hr Change 0.02%
Percent of Normal 100%
Minimum 743.62 ft
2021-10-22
Maximum 791.18 ft
2022-06-13
Average 752 ft
Dam_Height 81
Hydraulic_Height 76
Drainage_Area 104
Year_Completed 1942
Nid_Storage 50000
Structural_Height 103
Foundations Rock, Soil
Surface_Area 1158
Hazard_Potential High
River_Or_Stream COAST FORK WILLAMETTE RIVER
Dam_Length 2110
Primary_Dam_Type Earth
Nid_Height 103
       
Seasonal Comparison
Lake Or Reservoir Water Surface Elevation Above Ngvd 1929, Ft Levels

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.