Johnson Reservoir
Key Takeaway
Johnson Reservoir is classified as low hazard in Montana. It was completed in 1937 and is 89 years old. Its primary use is recreation.
Physical Details
| Dam Height | 21 ft (taller than 61.7% in MT) |
| Dam Length | 1,500 ft |
| Dam Type | Earth |
| Max Storage | 351 acre-ft |
| Normal Storage | 208 acre-ft |
| Surface Area | 36 acres |
| Drainage Area | 18 sq mi |
| Year Completed | 1937 (89 years old) |
| NID ID | MT00110 |
Safety Information
No probable loss of human life and low economic/environmental losses expected.
Hazard potential describes downstream consequences of failure, not the dam's current condition. What does this mean?
Ownership
STATE OF MONTANA, D.F.W.P.
State Government
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Low Hazard 30 ftFrequently Asked Questions
What is the hazard classification of Johnson Reservoir?
Johnson Reservoir is classified as Low Hazard. No probable loss of human life and low economic/environmental losses expected. This classification refers to the potential downstream consequences of a failure, not the dam's current structural condition.
Who owns and operates Johnson Reservoir?
Johnson Reservoir is owned by STATE OF MONTANA, D.F.W.P. (State Government). The owner is responsible for maintenance, inspections, and compliance with dam safety regulations.
When was Johnson Reservoir built?
Johnson Reservoir was completed in 1937, making it 89 years old. Many U.S. dams were built between the 1930s and 1970s during a period of major infrastructure investment.
What is the primary purpose of Johnson Reservoir?
Johnson Reservoir serves the following purposes: Recreation. Many dams in the U.S. are multi-purpose, supporting flood control, water supply, recreation, and other uses.
How tall is Johnson Reservoir?
Johnson Reservoir has a dam height of 21 ft. Dam height is measured from the natural streambed at the downstream toe to the top of the dam, and may differ from the visible height.
When was Johnson Reservoir last inspected?
Johnson Reservoir was last inspected on June 9, 2022. Inspection dates indicate when a formal review occurred, not the results of that inspection.