Grandfather Falls
Grandfather Falls is a gravity dam located in Lincoln County, Wisconsin, built in 1906. It carries a High hazard potential classification and has a satisfactory condition assessment.
About Grandfather Falls
The primary purpose of Grandfather Falls is hydroelectric. The dam generates hydroelectric power by channeling water through turbines, converting the energy of flowing water into electricity. The dam is owned by Wisconsin Public Service Corporation (public utility). It impounds the Wisconsin River near Merrill.
The dam stands 32 feet tall and stretches 700 feet across, creates a reservoir covering 200 acres, has a maximum storage capacity of 2,450 acre-feet, and collects water from a drainage area of 2,293 square miles. Completed in 1906, the structure is over a century old.
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 07/20/2022.
At 32 feet, this dam is taller than 76% of dams nationwide.
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 Wisconsin 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 | Wisconsin |
| County | Lincoln |
| Nearest City | Merrill |
| River/Stream | Wisconsin River |
| Coordinates | 45.31330, -89.78500 |
Physical Characteristics
| Dam Type | Gravity |
| NID Height | 32 ft |
| Dam Height | 32 ft |
| Dam Length | 700 ft |
| Year Completed | 1906 (120 years old) |
Storage & Hydraulics
| NID Storage | 2,540 acre-ft |
| Max Storage | 2,450 acre-ft |
| Normal Storage | 2,540 acre-ft |
| Surface Area | 200 acres |
| Drainage Area | 2,293 sq mi |
| Max Discharge | 59,830 cfs |
| Spillway Type | Controlled |
Ownership & Safety
| Purpose | Hydroelectric |
| Owner | Wisconsin Public Service Corporation |
| Owner Type | Public Utility |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 07/20/2022 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | WI00743 |
| Federal ID | WI00743 |
| More Info | State Dam Safety Program |