Willow
Willow is a gravity dam located in Oneida County, Wisconsin, built in 1927. It carries a High hazard potential classification and has a satisfactory condition assessment.
About Willow
The primary purpose of Willow 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 Valley Improvement Company (public utility). It impounds the Tomahawk River near Tomahawk.
The dam stands 35 feet tall and stretches 1,072 feet across, has a maximum storage capacity of 67,126 acre-feet, and collects water from a drainage area of 310 square miles. Completed in 1927, 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 08/04/2022.
At 35 feet, this dam is taller than 82% 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 | Oneida |
| Nearest City | Tomahawk |
| River/Stream | Tomahawk River |
| Coordinates | 45.71240, -89.84470 |
Physical Characteristics
| Dam Type | Gravity |
| NID Height | 35 ft |
| Dam Height | 35 ft |
| Dam Length | 1,072 ft |
| Year Completed | 1927 (99 years old) |
Storage & Hydraulics
| NID Storage | 67,126 acre-ft |
| Max Storage | 67,126 acre-ft |
| Normal Storage | 67,126 acre-ft |
| Drainage Area | 310 sq mi |
| Max Discharge | 12,800 cfs |
| Spillway Type | Controlled |
Ownership & Safety
| Purpose | Hydroelectric |
| Owner | Wisconsin Valley Improvement Company |
| Owner Type | Public Utility |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 08/04/2022 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | WI00774 |
| Federal ID | WI00774 |
| More Info | State Dam Safety Program |