Johnson (Toole) Reservoir Report
Nearby: Three Dollar Bill Sagittaurius
Last Updated: December 5, 2025
Johnson (Toole) is a private-owned irrigation dam located in Toole, Montana, along the TR-DUNKIRK COULEE river.
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Summary
Built in 1953 by the USDA NRCS, this earth dam stands at 15 feet high and stretches 830 feet long, with a storage capacity of 186 acre-feet. The dam is regulated by the DNRC and is in a low hazard potential category, with a moderate risk assessment rating.
The Johnson (Toole) dam serves as a vital water resource for the surrounding area, providing irrigation for agricultural purposes. Despite its age, the dam's condition is currently not rated, and it has not been inspected recently. It features an uncontrolled spillway with a width of 100 feet, capable of handling a maximum discharge of 600 cubic feet per second. The dam is situated in a picturesque location in the city of DEVON, Montana, with a beautiful surface area and a drainage area of 6.25 square miles.
Enthusiasts of water resources and climate in Montana will find Johnson (Toole) dam to be an intriguing structure with historical significance. With its unique design and purpose, this dam represents the intersection of human ingenuity and environmental stewardship. As efforts continue to manage and maintain this essential infrastructure, it remains a symbol of the ongoing balance between water resource utilization and conservation in the region.
Year Completed |
1953 |
Dam Length |
830 |
Dam Height |
15 |
River Or Stream |
TR-DUNKIRK COULEE |
Primary Dam Type |
Earth |
Hydraulic Height |
15 |
Drainage Area |
6.25 |
Nid Storage |
186 |
Hazard Potential |
Low |
Nid Height |
15 |
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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.
Johnson (Toole)