Horgan Reservoir Reservoir Report
Nearby: A Nichols Dubbe Reservoir
Last Updated: December 20, 2025
Horgan Reservoir, located in Valley County, Montana, is a privately owned water storage facility completed in 1952 for fire protection, stock, and small fish pond purposes.
°F
°F
mph
Wind
%
Humidity
Summary
With a dam height of 20 feet and a storage capacity of 258 acre-feet, the reservoir is situated along the TR-Oswego Creek and is regulated by the Montana Department of Natural Resources and Conservation. Despite its low hazard potential, the dam has not been rated for its condition, and there is no recent inspection data available.
The reservoir's location in the scenic city of Oswego offers a tranquil setting for water resource and climate enthusiasts to explore the impact of this essential water source on the local ecosystem. Serving as a vital water supply for firefighting efforts and livestock watering, Horgan Reservoir plays a crucial role in supporting the surrounding community's agricultural and environmental needs. The reservoir's construction and maintenance align with state regulations and permit requirements, ensuring its safe and sustainable operation for years to come.
As a key feature in the region's water management infrastructure, Horgan Reservoir contributes to the overall water security and resource resilience in Valley County. Its modest size and purposeful design reflect a thoughtful approach to managing water resources for multiple uses while minimizing potential risks. While the dam's condition assessment is pending, ongoing regulatory oversight and enforcement by the state agency help maintain the reservoir's integrity and safeguard its continued functionality for the benefit of the local population and ecosystem.
Year Completed |
1952 |
Dam Length |
200 |
Dam Height |
20 |
River Or Stream |
TR-OSWEGO CREEK |
Primary Dam Type |
Earth |
Hydraulic Height |
20 |
Nid Storage |
258 |
Hazard Potential |
Low |
Nid Height |
20 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Milk River At Nashua Mt
|
233cfs |
Missouri River Near Wolf Point Mt
|
5020cfs |
Poplar River Near Poplar Mt
|
28cfs |
Milk River At Tampico Mt
|
123cfs |
Nelson Creek Near Van Norman Mt
|
33cfs |
Poplar River At International Boundary
|
4cfs |
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.
Horgan Reservoir