Rieger
Rieger is an earth dam located in Fallon County, Montana, built in 1958. It carries a Significant hazard potential classification.
About Rieger
The primary purpose of Rieger is irrigation. The dam stores and diverts water for agricultural irrigation, supporting farming operations in the surrounding area. The dam is owned by Donald Rieger (private). It impounds the South Fork Cottonwood Creek near Ismay.
The dam stands 21 feet tall and stretches 300 feet across, creates a reservoir covering 13 acres, has a storage capacity of 92 acre-feet, and collects water from a drainage area of 6,976 square miles. Completed in 1958, the structure is well into its service life at over 50 years old.
This dam has a significant hazard potential classification, meaning that a failure could cause significant economic damage — flooding roads, bridges, or property downstream — but is not expected to result in loss of life.
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Location
| State | Montana |
| County | Fallon |
| Nearest City | Ismay |
| River/Stream | South Fork Cottonwood Creek |
| Coordinates | 46.42190, -104.83370 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 21 ft |
| Dam Height | 21 ft |
| Dam Length | 300 ft |
| Year Completed | 1958 (68 years old) |
Storage & Hydraulics
| NID Storage | 92 acre-ft |
| Normal Storage | 92 acre-ft |
| Surface Area | 13 acres |
| Drainage Area | 6,976 sq mi |
Ownership & Safety
| Purpose | Irrigation |
| Owner | DONALD RIEGER |
| Owner Type | Private |
| Hazard Classification | Significant |
| Emergency Action Plan | Not Required |
Identifiers
| NID ID | MT01043 |
| Federal ID | MT01043 |
| More Info | State Dam Safety Program |