Lonesome Reservoir Report

Last Updated: December 5, 2025

Lonesome is a privately owned dam located in Phillips County, Montana, near the city of Saco.


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Summary

Built in 1946, this earth dam stands at a height of 16 feet and serves multiple purposes, including fire protection, stock watering, and as a small fish pond. The dam has a storage capacity of 216 acre-feet, with a normal storage level of 91 acre-feet.

Situated on the Lonesome Coulee river or stream, this dam plays a crucial role in water resource management in the region. While it has a low hazard potential, its condition assessment has not been rated. The state regulatory agency, DNRC, oversees the operation, inspection, and enforcement of safety measures at Lonesome dam. With its strategic location and vital functions, Lonesome serves as a valuable asset for maintaining water resources and addressing the needs of the surrounding community.

Despite its age, Lonesome continues to provide essential services for fire protection and agricultural activities in the area. As a key infrastructure for water management, it highlights the importance of sustainable resource utilization and the role of private ownership in ensuring the resilience of water systems. Climate enthusiasts and water resource stakeholders can appreciate the significance of Lonesome in supporting local needs and safeguarding the environment in Phillips County, Montana.

Year Completed

1946

Dam Length

250

Dam Height

16

River Or Stream

LONESOME COULEE

Primary Dam Type

Earth

Hydraulic Height

16

Nid Storage

216

Hazard Potential

Low

Nid Height

16
       
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.