Willow Creek Dam Reservoir Report

Last Updated: December 5, 2025

Willow Creek Dam, located in Madison, Montana, is a state-regulated structure built in 1938 primarily for irrigation purposes along the Willow Creek river.


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Summary

The dam stands at an impressive height of 105 feet, with a hydraulic height of 96.5 feet, and a length of 453 feet. It has a storage capacity of 26,600 acre-feet, with a normal storage level of 18,000 acre-feet, covering a surface area of 885 acres.

Despite its significant contribution to irrigation in the area, Willow Creek Dam is currently rated as having a high hazard potential and a poor condition assessment. The last inspection in March 2021 identified concerns, prompting a need for immediate attention to address the dam's deteriorating condition. The emergency action plan (EAP) for the dam was last revised in January 2022, indicating ongoing efforts to ensure public safety in case of an emergency.

The dam's risk assessment is classified as moderate, with a DSAC (Dam Safety Action Classification) of 3. While the structure's risk management measures are not specified, the dam's condition and hazard potential highlight the importance of continued monitoring and maintenance to safeguard the surrounding community and water resources. Enthusiasts interested in water resource management and climate resilience would find Willow Creek Dam an intriguing case study for understanding the complexities of balancing water supply needs with infrastructure safety and environmental impacts.

Year Completed

1938

Dam Length

453

Dam Height

105

River Or Stream

WILLOW CREEK

Primary Dam Type

Earth

Surface Area

885

Hydraulic Height

96.5

Drainage Area

155

Nid Storage

26600

Outlet Gates

Slide (sluice gate)

Hazard Potential

High

Foundations

Rock, Soil

Nid Height

105
       
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.