Tongue River Dam Reservoir Report

Last Updated: December 5, 2025

Tongue River Dam, located in Big Horn, Montana, is a key water resource infrastructure that plays a crucial role in irrigation in the area.


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Summary

Completed in 1939, this Earth-type dam stands at a height of 93 feet and has a maximum storage capacity of 127,655 acre-feet. The dam spans 1,824 feet in length and has a spillway width of 650 feet, showcasing its significant hydraulic capabilities.

Managed by the Montana state regulatory agency DNRC, Tongue River Dam is inspected regularly to ensure its structural integrity and safety. With a high hazard potential and a very high risk assessment rating, the dam's condition is currently assessed as satisfactory. In the event of an emergency, the dam's Emergency Action Plan (EAP) is regularly updated to meet guidelines and ensure the safety of surrounding communities.

Enthusiasts of water resources and climate will find Tongue River Dam to be a fascinating example of infrastructure designed to support agricultural activities in the region. Its strategic location and impressive hydraulic features underscore its importance in water management and highlight the ongoing efforts to maintain its safety and efficiency for the benefit of all stakeholders involved.

Year Completed

1939

Dam Length

1824

Dam Height

93

River Or Stream

TONGUE RIVER

Primary Dam Type

Earth

Surface Area

3700

Hydraulic Height

91

Drainage Area

1760

Nid Storage

127655

Hazard Potential

High

Foundations

Rock

Nid Height

93
       
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.