Cascade Reservoir Report

Last Updated: December 19, 2025

Cascade is a federal hydroelectric dam located in Idaho, specifically in the city of Cascade along the North Fork Payette River.


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Summary

Built in 1948 by the Bureau of Reclamation, Cascade serves multiple purposes including hydroelectric power generation and irrigation. With a dam height of 110 feet and a storage capacity of 860,000 acre-feet, Cascade covers a surface area of 27,700 acres and has a maximum discharge of 12,500 cubic feet per second.

This rockfill dam has a controlled spillway with a width of 42 feet and is regulated by the Bureau of Reclamation. The dam's hazard potential is classified as high, with a very high risk assessment score. Despite its age, Cascade's condition assessment is currently listed as not available, indicating a need for further inspection and evaluation. The Emergency Action Plan (EAP) for Cascade has not been updated recently, raising concerns about the readiness and response protocols in case of emergencies.

Water resource and climate enthusiasts can appreciate the significance of Cascade as a key infrastructure for water management in Idaho. As a critical component of the region's hydroelectric and irrigation systems, Cascade represents a complex engineering feat with implications for water supply, energy production, and environmental stewardship. Continued monitoring and maintenance of Cascade are essential to ensure the safety and sustainability of this important water resource infrastructure.

Year Completed

1948

Dam Length

785

Dam Height

110

River Or Stream

NORTH FORK PAYETTE RIVER PAYETTE RIVER

Primary Dam Type

Rockfill

Surface Area

27700

Hydraulic Height

75

Drainage Area

2230

Nid Storage

860000

Structural Height

107

Hazard Potential

High

Foundations

Rock, Soil

Nid Height

110
       
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.