Manley #2 Reservoir Report

Last Updated: December 5, 2025

Manley #2 is a privately owned irrigation dam located in Powell County, Montana, near the city of Helmville.


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Summary

This earth dam, completed in 1964, serves the primary purpose of providing water for irrigation from the Douglas Creek. With a dam height of 25 feet and a length of 500 feet, it has a storage capacity of 93 acre-feet and a drainage area of 16.8 square miles. The dam has a significant hazard potential and is regulated by the Montana Department of Natural Resources and Conservation.

Managed by the USDA NRCS, Manley #2 is situated in a picturesque location with a spillway width of 90 feet. Despite not having a condition rating, the dam has not been rated as of yet. It has not undergone recent inspections or been assessed for emergency action plans. As a crucial water resource infrastructure in the region, ensuring the safety and efficacy of Manley #2 remains essential for sustainable water management and climate resilience efforts.

Water resource and climate enthusiasts in the area will appreciate the historical significance and environmental impact of Manley #2. With its vital role in supporting agricultural activities through irrigation, this dam serves as a reminder of the importance of sustainable water management practices. The data provided offers valuable insights into the dam's design, construction, and regulatory oversight, highlighting the need for continued monitoring and maintenance to ensure the safety and reliability of this essential water infrastructure in Montana.

Year Completed

1964

Dam Length

500

Dam Height

25

River Or Stream

DOUGLAS CREEK

Primary Dam Type

Earth

Hydraulic Height

25

Drainage Area

16.8

Nid Storage

93

Hazard Potential

Significant

Nid Height

25
       
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.