Ruby Dam
Ruby Dam is an earth dam located in Madison County, Montana, built in 1938. It carries a High hazard potential classification and has a satisfactory condition assessment.
About Ruby Dam
The primary purpose of Ruby Dam is irrigation. The dam stores and diverts water for agricultural irrigation, supporting farming operations in the surrounding area. The dam is owned by State Water Projects (state). It impounds the Ruby River near Alder.
The dam stands 111 feet tall and stretches 846 feet across, creates a reservoir covering 970 acres, has a maximum storage capacity of 56,355 acre-feet, and collects water from a drainage area of 595 square miles. Completed in 1938, the structure is well-established, with more than 75 years of service.
This dam carries a high hazard potential classification, which means that a failure or uncontrolled release of water would likely cause loss of human life. This classification reflects the consequences of failure, not the likelihood — it indicates that people live or work in the area downstream. Its condition is rated satisfactory, indicating no existing or potential dam safety deficiencies are recognized. An emergency action plan is in place for this dam. The most recent inspection on record was 05/31/2024.
At 111 feet, this dam is taller than 98% of all dams in the United States.
Living Downstream
If you live or work downstream of this dam, consider taking these steps: learn your local evacuation routes, check whether your county emergency management office has a dam failure inundation map, and sign up for local emergency alerts. The Montana dam safety program can provide more specific information about emergency planning for this structure.
Search for dams near your address to see all dams in your area with hazard classifications and safety data.
Location
| State | Montana |
| County | Madison |
| Nearest City | Alder |
| River/Stream | Ruby River |
| Coordinates | 45.23940, -112.11050 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 111 ft |
| Dam Height | 111 ft |
| Dam Length | 846 ft |
| Year Completed | 1938 (88 years old) |
Storage & Hydraulics
| NID Storage | 56,355 acre-ft |
| Max Storage | 56,355 acre-ft |
| Normal Storage | 37,611 acre-ft |
| Surface Area | 970 acres |
| Drainage Area | 595 sq mi |
| Max Discharge | 36,000 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Irrigation |
| Owner | STATE WATER PROJECTS |
| Owner Type | State |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 05/31/2024 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | MT00004 |
| Federal ID | MT00004 |
| More Info | State Dam Safety Program |