Thebes Lake Reservoir Report
Nearby: L Olson #1 Montana #19
Last Updated: December 6, 2025
Thebes Lake, located in Montana, is a private water resource regulated by the state's Department of Natural Resources and Conservation (DNRC).
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Summary
This Earth dam was completed in 1913 and serves a primary purpose other than irrigation or flood control. With a dam height of 16 feet and a storage capacity of 94 acre-feet, Thebes Lake has a low hazard potential and its condition is currently not rated.
Situated in Rosebud County near the town of Hammond, Thebes Lake is fed by the Sun Coulee river. The dam spans 1100 feet and has a normal storage capacity of 40 acre-feet. Although not currently assessed for condition, it is under state jurisdiction with permitting, inspection, and enforcement processes in place. The lake's location and purpose make it an interesting site for water resource and climate enthusiasts to explore and study.
The history and features of Thebes Lake make it a unique and valuable resource in Montana. While not a high-risk dam, its presence and management contribute to the state's overall water infrastructure. The lake's purpose and low hazard potential, along with its scenic location, make it an intriguing destination for those interested in water conservation and climate-related issues.
Year Completed |
1913 |
Dam Length |
1100 |
Dam Height |
16 |
River Or Stream |
SUN COULEE |
Primary Dam Type |
Earth |
Hydraulic Height |
16 |
Nid Storage |
94 |
Hazard Potential |
Low |
Nid Height |
16 |
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.
Thebes Lake