East Blacktail Reservoir Report
Last Updated: December 7, 2025
East Blacktail is a privately owned irrigation dam located in Forsyth, Montana, along the East Blacktail Creek.
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Summary
Built in 1952 by the USDA NRCS, this earth dam stands at a height of 25 feet and has a storage capacity of 947 acre-feet. With a drainage area of 46.88 square miles, the dam is designed to regulate water flow for agricultural purposes in the region.
Managed by the DNRC and regulated by the state of Montana, East Blacktail has a significant hazard potential and is classified as not rated in terms of condition assessment. The dam has a spillway width of 400 feet and a maximum discharge capacity of 2000 cubic feet per second. Despite lacking recent inspection data, the dam is equipped to handle emergencies with emergency action plans in place, though their current status is unclear.
Located in Rosebud County, Montana, East Blacktail serves as a crucial water resource for irrigation in the region. With its strategic location and contribution to water management in the area, the dam remains an essential infrastructure for sustainable agriculture and climate resilience efforts.
Year Completed |
1952 |
Dam Length |
2825 |
Dam Height |
25 |
River Or Stream |
EAST BLACKTAIL CREEK |
Primary Dam Type |
Earth |
Hydraulic Height |
25 |
Drainage Area |
46.88 |
Nid Storage |
947 |
Hazard Potential |
Significant |
Nid Height |
25 |
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.
East Blacktail