Twin Falls Reservoir Report

Last Updated: December 23, 2025

Twin Falls, located in Jerome, Idaho, is a privately-owned concrete dam with a primary purpose of generating hydroelectric power.


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Summary

Built in 1935 by EBASCO, this structure also serves recreational purposes, attracting water resource and climate enthusiasts to its scenic surroundings. The dam stands at a height of 16 feet and has a hydraulic height of 19.4 feet, with a storage capacity of 955 acre-feet in the Snake River.

Managed by the Federal Energy Regulatory Commission, Twin Falls is regulated at both the state and federal levels, ensuring compliance with safety and operational standards. The dam has a low hazard potential and a moderate risk assessment score, with regular inspections every three years to maintain its structural integrity. With an uncontrolled spillway and a maximum discharge capacity of 60,000 cubic feet per second, Twin Falls plays a crucial role in water management and energy production in the region.

Despite its age, Twin Falls continues to be a reliable source of hydroelectric power and a popular destination for outdoor recreation. With its picturesque setting and historical significance, this dam stands as a testament to the enduring impact of water resource infrastructure on both the environment and local communities.

Year Completed

1935

Dam Length

809

Dam Height

16

River Or Stream

Snake River

Primary Dam Type

Concrete

Surface Area

85

Hydraulic Height

19.4

Drainage Area

19000

Nid Storage

955

Structural Height

19.4

Hazard Potential

Low

Nid Height

19
       
Seasonal Comparison

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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.