Lower Blacktail Reservoir Reservoir Report
Last Updated: December 7, 2025
Lower Blacktail Reservoir, located in Rosebud, Montana, is a privately owned earth dam that was completed in 1955.
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Summary
The reservoir serves multiple purposes including fire protection, stock watering, and as a small fish pond. With a dam height of 20 feet and a storage capacity of 145 acre-feet, Lower Blacktail Reservoir provides vital water resources for the surrounding area.
Managed by the DNRC and regulated by the state of Montana, Lower Blacktail Reservoir has a low hazard potential and is currently rated as "Not Rated" in terms of its condition assessment. Despite lacking specific data on surface area and drainage area, the reservoir's normal storage capacity of 74 acre-feet plays a crucial role in maintaining water availability in the region. With its strategic location along TR-East Blacktail Creek, Lower Blacktail Reservoir is a key component of the local water resource infrastructure.
Although there are no associated structures or outlet gates listed for Lower Blacktail Reservoir, its importance for fire protection and livestock watering cannot be understated. As a valuable water source in the region, the reservoir's role in climate adaptation and drought resilience is significant. With state-mandated inspections, enforcement, and permitting in place, Lower Blacktail Reservoir remains a reliable and essential resource for the community of Forsyth and the surrounding areas.
Year Completed |
1955 |
Dam Length |
125 |
Dam Height |
20 |
River Or Stream |
TR-EAST BLACKTAIL CREEK |
Primary Dam Type |
Earth |
Hydraulic Height |
20 |
Nid Storage |
145 |
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.
Lower Blacktail Reservoir