Diomedes Reservoir Report

Last Updated: December 5, 2025

Diomedes is a private water resource structure located in VIRELLE, Montana, specifically on the DRY FORK COULEE river.


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Summary

Completed in 1947, this earth dam stands at 20 feet in height and spans 500 feet in length, with a primary purpose of serving as a fire protection, stock, or small fish pond. It has a storage capacity of 51 acre-feet, with a normal storage level of 26 acre-feet.

Managed by the DNRC and regulated by the state of Montana, Diomedes has a low hazard potential and is currently rated as 'Not Rated' in terms of condition assessment. While the structure has not been inspected recently, it is equipped with state-permitted and state-inspected features for continued safety and functionality. The dam also falls under Congressional District 00, Montana, represented by Greg Gianforte (R). With its strategic location and purposeful design, Diomedes serves as a vital resource for fire protection and livestock management in Chouteau County, Montana.

Year Completed

1947

Dam Length

500

Dam Height

20

River Or Stream

DRY FORK COULEE

Primary Dam Type

Earth

Hydraulic Height

20

Nid Storage

51

Hazard Potential

Low

Nid Height

20
       
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.