Hells Canyon Reservoir Report

Last Updated: December 13, 2025

Hells Canyon, located in Idaho along the Snake River, is a privately owned hydroelectric dam that was completed in 1967.


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Summary

This gravity dam stands at a height of 323 feet, with a structural height of 330 feet and a length of 910 feet. With a normal storage capacity of 170,000 acre-feet and a maximum storage of 188,000 acre-feet, the dam covers a surface area of 2,430 acres and serves multiple purposes including hydroelectric power generation, navigation, and recreation.

Managed by the Federal Energy Regulatory Commission, Hells Canyon Dam has a controlled spillway with a width of 159 feet and five Tainter (radial) gates for outlet control. The dam's hazard potential is classified as high, with a very high risk assessment rating. While the condition assessment is not available, the dam's emergency action plan was last revised in April 2021. With its impressive engineering design and significant impact on the surrounding environment and water resources, Hells Canyon Dam remains a notable structure for water resource and climate enthusiasts to study and explore in the picturesque setting of Adams County, Idaho.

Year Completed

1967

Dam Length

910

Dam Height

323

River Or Stream

Snake River

Primary Dam Type

Gravity

Surface Area

2430

Hydraulic Height

323

Drainage Area

73300

Nid Storage

188000

Structural Height

330

Outlet Gates

Tainter (radial) - 5

Hazard Potential

High

Nid Height

330
       
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.