Diamond A Reservoir Report

Last Updated: January 11, 2026

Diamond A is a privately owned dam located in Owyhee, Idaho, along Cougar Creek and the Jarbidge River.


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Summary

Built in 1931, this earth dam stands at a height of 28.8 feet and has a hydraulic height of 26.3 feet. With a storage capacity of 3926 acre-feet and a surface area of 325 acres, Diamond A plays a crucial role in water resource management in the region.

Despite its age, Diamond A is in fair condition and has a low hazard potential, making it a reliable structure for water storage and flood control. The dam is regulated by the Idaho Department of Water Resources, which ensures regular inspections and maintenance to uphold its integrity. With a moderate risk assessment rating, Diamond A remains a vital component of the local water infrastructure, contributing to sustainable water management practices in the area.

Water resource enthusiasts and climate advocates can appreciate the significance of Diamond A in maintaining water quality and quantity in the Owyhee region. As a key structure along the Jarbidge River, this dam reflects the intersection of human engineering with natural water systems, highlighting the importance of responsible dam management in the face of climate change and evolving water resource challenges.

Year Completed

1931

Dam Length

350

Dam Height

28.8

River Or Stream

COUGAR CREEK JARBIDGE RIVER

Surface Area

325

Hydraulic Height

26.3

Drainage Area

31

Nid Storage

3926

Hazard Potential

Low

Foundations

Rock, Soil

Nid Height

29
       
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.