Bonanza Reservoir Report

Last Updated: December 5, 2025

Located in Martinsdale, Montana, the Bonanza dam stands as a vital structure along the Bonanza Creek, serving the purpose of irrigation since its completion in 1938.


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Summary

With a dam height of 44 feet and a storage capacity of 409 acre-feet, the dam plays a crucial role in supporting agricultural activities in the region. Managed by the Montana Department of Natural Resources and Conservation (DNRC), the dam is regulated and monitored to ensure its safety and functionality for the community it serves.

The Bonanza dam's significant hazard potential and moderate risk assessment highlight the importance of proper management and maintenance to prevent any potential emergencies. Despite being classified as "Not Rated" in terms of condition assessment, the dam's construction and operation are regulated by the state, with regular inspections and enforcement measures in place. The dam's uncontrolled spillway and earth dam type further emphasize the need for vigilance and preparedness in managing water resources and climate-related risks in the area.

Enthusiasts of water resources and climate in Montana will find the Bonanza dam an intriguing subject, with its historical significance, hydraulic capabilities, and regulatory framework providing valuable insights into the intersection of human infrastructure and natural elements. As a key player in the irrigation system of the region, the dam's role in water management and agricultural sustainability underscores the importance of balanced resource utilization and risk management in the face of changing environmental conditions.

Year Completed

1938

Dam Length

1020

Dam Height

44

River Or Stream

BONANZA CREEK

Primary Dam Type

Earth

Surface Area

25

Hydraulic Height

40

Drainage Area

7.72

Nid Storage

409

Hazard Potential

Significant

Nid Height

44
       
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.
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Area Campgrounds