Big Timber #20 Reservoir Report
Nearby: Big Timber #17 Big Timber #16
Last Updated: December 6, 2025
Big Timber #20 is a privately owned earth dam located in Forsyth, Montana, with a primary purpose of fire protection, stock watering, and small fish pond.
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Summary
Built in 1959 by the USDA NRCS, this dam stands at a height of 20 feet and has a storage capacity of 82 acre-feet. Situated on TR-West Blacktail Creek, the dam serves as a critical water resource for the surrounding area, with a drainage area of 2.5 square miles.
With a low hazard potential and a moderate risk assessment rating of 3, Big Timber #20 is regulated by the Montana Department of Natural Resources and Conservation. The dam has not been rated for its current condition, but it undergoes state inspections and enforcement to ensure its safety and functionality. While it does not have an Emergency Action Plan in place, the dam's risk management measures are in the process of being assessed and implemented to mitigate potential hazards.
Overall, Big Timber #20 is an essential water infrastructure project that plays a vital role in providing water resources for fire protection, livestock, and aquatic life in the region. As climate change continues to impact water availability and quality, dams like Big Timber #20 will play an increasingly important role in managing and conserving water resources for future generations.
Year Completed |
1959 |
Dam Length |
200 |
Dam Height |
20 |
River Or Stream |
TR-WEST BLACKTAIL CREEK |
Primary Dam Type |
Earth |
Hydraulic Height |
20 |
Drainage Area |
2.5 |
Nid Storage |
82 |
Hazard Potential |
Low |
Nid Height |
20 |
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.
Big Timber #20