Tiber Reservoir Report

Last Updated: December 6, 2025

Tiber Dam, located in Liberty County, Montana, along the Marias River, is a vital structure managed by the Bureau of Reclamation for flood risk reduction.


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Summary

Completed in 1955, this earth dam stands at 206 feet tall with a hydraulic height of 197 feet, providing essential water storage of up to 1.4 million acre-feet. With a primary purpose of flood risk reduction, Tiber Dam also serves irrigation, recreation, and water supply needs in the region.

The dam's controlled spillway, with a width of 66 feet, helps manage water flow and prevent potential hazards, earning it a high hazard potential rating. Although its condition assessment is not available, regular inspections by the Bureau of Reclamation ensure the dam's structural integrity. Tiber Dam's very high risk assessment underscores the critical role it plays in protecting the surrounding area from flooding events, highlighting the importance of ongoing risk management measures and emergency preparedness.

As a key infrastructure managed by federal agencies, Tiber Dam reflects the collaborative efforts to safeguard water resources and mitigate climate-related risks. Its strategic location, significant storage capacity, and multi-purpose functionality make it a crucial asset for water management in Montana, emphasizing the intersection of infrastructure, water resources, and climate resilience.

Year Completed

1955

Dam Length

4526

Dam Height

206

River Or Stream

MARIAS RIVER

Primary Dam Type

Earth

Surface Area

23805

Hydraulic Height

197

Drainage Area

4393

Nid Storage

1424478

Structural Height

206

Hazard Potential

High

Foundations

Rock

Nid Height

206
       
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.