Lois Lake Reservoir Report
Nearby: Christopher Columbus Gravely
Last Updated: December 5, 2025
Lois Lake, also known as Snowshoe Lake, is a privately owned reservoir located in Avon, Montana.
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Summary
Built in 1966 by the USDA NRCS, this earth dam serves primarily for irrigation purposes on Snowshoe Creek. With a height of 22.5 feet and a storage capacity of 288 acre-feet, Lois Lake covers a surface area of 25.9 acres and has a drainage area of 6.5 square miles.
Managed by the Montana Department of Natural Resources and Conservation (DNRC), Lois Lake has a low hazard potential and is currently rated as "Not Rated" in terms of condition assessment. The dam has a spillway width of 30 feet and a maximum discharge capacity of 230 cubic feet per second. Despite not being regulated by federal agencies, the dam is subject to state permitting, inspection, and enforcement requirements to ensure its safety and functionality.
For water resource and climate enthusiasts, Lois Lake presents an intriguing case study of a privately owned reservoir in a rural setting. Its historical significance, design characteristics, and state-regulated management offer valuable insights into the intersection of water infrastructure and environmental stewardship in the region. With its location in the picturesque Powell County, Montana, Lois Lake serves as a reminder of the importance of sustainable water management practices in the face of changing climate conditions.
Year Completed |
1966 |
Dam Length |
400 |
Dam Height |
22.5 |
River Or Stream |
SNOWSHOE CREEK |
Primary Dam Type |
Earth |
Surface Area |
25.9 |
Hydraulic Height |
16.5 |
Drainage Area |
6.5 |
Nid Storage |
288 |
Hazard Potential |
Low |
Nid Height |
23 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Tenmile Creek Near Rimini Mt
|
1cfs |
Nevada Cr Ab Reservoir
|
27cfs |
Little Blackfoot River Near Garrison Mt
|
117cfs |
Tenmile Creek Near Helena Mt
|
16cfs |
Clark Fork At Deer Lodge Mt
|
156cfs |
Clark Fork At Goldcreek Mt
|
248cfs |
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.
Lois Lake