Virgil Larson Reservoir Report
Nearby: Rattlesnake #2 J Witkowski #1
Last Updated: December 5, 2025
Virgil Larson is a private irrigation dam located in Wibaux, Montana, along the TR-Rattlesnake Creek.
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Summary
Built in 1977 by the USDA NRCS, this earth dam stands 16 feet high and has a storage capacity of 210 acre-feet. With a normal storage level of 75 acre-feet and a drainage area of 2.02 square miles, Virgil Larson plays a crucial role in providing water for agricultural purposes in the region.
Maintained by the Montana Department of Natural Resources and Conservation (DNRC), Virgil Larson is classified as a low hazard potential dam with a condition assessment that is currently not rated. While the dam's spillway type is unspecified, it has a spillway width of 30 feet and a maximum discharge capacity of 1500 cubic feet per second. Despite its modest size, Virgil Larson serves as a vital water resource infrastructure for the surrounding community and contributes to the sustainable management of water in the area.
With its strategic location and functional design, Virgil Larson exemplifies the importance of private irrigation dams in enhancing water security and supporting agricultural activities. As a key component of the local water management system, this dam underscores the collaborative efforts between private owners and state agencies to ensure the efficient utilization of water resources while minimizing potential risks and environmental impacts. For water resource and climate enthusiasts, Virgil Larson represents a notable example of how irrigation infrastructure can play a significant role in promoting water sustainability and resilience in a changing climate.
Year Completed |
1977 |
Dam Length |
800 |
Dam Height |
16 |
River Or Stream |
TR-RATTLESNAKE CREEK |
Primary Dam Type |
Earth |
Surface Area |
18 |
Hydraulic Height |
10 |
Drainage Area |
2.02 |
Nid Storage |
210 |
Hazard Potential |
Low |
Nid Height |
16 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Little Missouri River At Marmarth
|
12cfs |
Deep Creek Nr Amidon
|
0cfs |
Beaver Creek Nr Trotters
|
0cfs |
Yellowstone River At Glendive Mt
|
6000cfs |
Little Missouri River At Medora
|
64cfs |
Powder River Near Locate Mt
|
231cfs |
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.
Virgil Larson