Willow Creek Bor Mt Reservoir Report
Last Updated: December 5, 2025
Willow Creek Bor Mt, located in Lewis and Clark County, Montana, is a Federal-owned irrigation reservoir on Willow Creek.
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Summary
Built in 1911, this Earth-type dam stands at 93 feet high and spans 650 feet in length, providing a storage capacity of 39,800 acre-feet for irrigation purposes. The dam has a Hazard Potential rating of High (2) due to its age and structural integrity, with modifications made in 1998 and 2000 to address seismic and structural concerns.
Managed by the Bureau of Reclamation, Willow Creek Bor Mt is a critical water resource in the region, serving agricultural needs in the area. The dam has a surface area of 1,470 acres and drains a watershed area of 95 square miles. While it does not have a spillway, the dam has a hydraulic height of 69 feet and a maximum storage capacity of 39,800 acre-feet. With its last inspection in June 2020 and an Inspection Frequency of 1, the dam's condition assessment is currently listed as Not Available, highlighting the need for continued monitoring and maintenance.
Despite its age and High Hazard Potential, Willow Creek Bor Mt plays a vital role in water management and irrigation in the region. With its historical significance dating back over a century, the dam stands as a testament to the engineering feats of the past while also serving as a reminder of the importance of ongoing risk assessment and management in safeguarding our water resources in the face of changing climate conditions.
Years Modified |
1998 - Structural, 2000 - Seismic, 2000 - Structural |
Year Completed |
1911 |
Dam Length |
650 |
Dam Height |
74 |
River Or Stream |
WILLOW CREEK |
Primary Dam Type |
Earth |
Surface Area |
1470 |
Hydraulic Height |
69 |
Drainage Area |
95 |
Nid Storage |
39800 |
Structural Height |
93 |
Hazard Potential |
High |
Foundations |
Unlisted/Unknown |
Nid Height |
93 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Dam Data Reference
Condition Assessment
SatisfactoryNo 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
HighDams 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.
Area Campgrounds
| Location | Reservations | Toilets |
|---|---|---|
Willow Creek FAS
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Nilan Reservoir FAS
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Pishkun Reservoir FAS
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Willow Creek Bor Mt