Gollaher Reservoir is an earth dam located in Cascade County, Montana, built in 1945. It carries a Significant hazard potential classification.
Dam profile
NID height · 38 ft38 ft tall and 1,130 ft long, taller than 84% of U.S. dams with a recorded height. Height is drawn to scale against a two-story house, about 25 ft; the profile is a generic embankment section and the water level is illustrative.
About Gollaher Reservoir
The primary purpose of Gollaher Reservoir is irrigation. The dam stores and diverts water for agricultural irrigation, supporting farming operations in the surrounding area. The dam is owned by Gollaher Ranch Co. (private). It impounds the Willow Creek near Ulm.
The dam stands 38 feet tall and stretches 1,130 feet across, creates a reservoir covering 41 acres, has a maximum storage capacity of 827 acre-feet, and collects water from a drainage area of 10 square miles. Completed in 1945, the structure is well-established, with more than 75 years of service.
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.
At 38 feet, this dam is taller than 84% of dams nationwide.
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Location
| State | Montana |
| County | Cascade |
| Nearest City | Ulm |
| River/Stream | Willow Creek |
| Coordinates | 47.22190, -111.62050 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 38 ft |
| Dam Height | 38 ft |
| Dam Length | 1,130 ft |
| Year Completed | 1945 (81 years old) |
Storage & Hydraulics
| NID Storage | 827 acre-ft |
| Max Storage | 827 acre-ft |
| Normal Storage | 613 acre-ft |
| Surface Area | 41 acres |
| Drainage Area | 10 sq mi |
| Max Discharge | 525 cfs |
Ownership & Safety
| Purpose | Irrigation |
| Owner | Gollaher Ranch Co. |
| Owner Type | Private |
| Hazard Classification | Significant |
| Condition Assessment | Not assessed |
| Emergency Action Plan | Not Required |
Identifiers
| NID ID | MT00204 |
| Federal ID | MT00204 |
| More Info | State Dam Safety Program |