Conconully Reservoir Report

Last Updated: December 13, 2025

Conconully is a historic earth dam located in Okanogan, Washington, built in 1909 by the Bureau of Reclamation for irrigation purposes.


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Summary

Standing at 72 feet tall with a hydraulic height of 63 feet, it harnesses the waters of Salmon Creek, providing a maximum storage capacity of 16,570 acre-feet and servicing a drainage area of 5 square miles. The dam covers a surface area of 450 acres and boasts a spillway width of 149 feet for uncontrolled discharge, with a maximum capacity of 11,580 cubic feet per second.

Managed by the Bureau of Reclamation, Conconully's hazard potential is classified as high, with a moderate risk assessment score of 3. The dam has not undergone a recent condition assessment, but emergency action plans have been prepared, last revised in September 2020. While the dam has not been modified in recent years, it remains a critical piece of infrastructure for the surrounding area, providing essential irrigation water to support agricultural activities. With its rich history and significant role in water resource management, Conconully stands as a testament to the importance of infrastructure in sustaining communities and ecosystems in Washington state.

Year Completed

1909

Dam Length

1075

Dam Height

72

River Or Stream

SALMON CREEK

Primary Dam Type

Earth

Surface Area

450

Hydraulic Height

63

Drainage Area

5

Nid Storage

16570

Structural Height

72

Hazard Potential

High

Foundations

Rock

Nid Height

72
       
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.