Arrowrock Dam
Arrowrock Dam is a concrete dam located in Boise County, Idaho, built in 1915. It carries a High hazard potential classification.
About Arrowrock Dam
The primary purpose of Arrowrock Dam is flood risk reduction. The dam is designed to control downstream flooding by temporarily storing excess water during storms and releasing it at a controlled rate. The dam is owned by Bureau Of Reclamation (federal). It impounds the Boise River Snake River near Boise.
The dam stands 350 feet tall and stretches 1,150 feet across, creates a reservoir covering 3,256 acres, has a maximum storage capacity of 272,224 acre-feet, and collects water from a drainage area of 2,216 square miles. Completed in 1915, 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. An emergency action plan is in place for this dam. The most recent inspection on record was 05/05/2021.
At 350 feet, this dam is taller than 99% 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 Idaho 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 | Idaho |
| County | Boise |
| Nearest City | Boise |
| River/Stream | Boise River Snake River |
| Coordinates | 43.59540, -115.92250 |
Physical Characteristics
| Dam Type | Concrete |
| NID Height | 350 ft |
| Dam Height | 350 ft |
| Dam Length | 1,150 ft |
| Year Completed | 1915 (111 years old) |
Storage & Hydraulics
| NID Storage | 272,224 acre-ft |
| Max Storage | 272,224 acre-ft |
| Normal Storage | 272,224 acre-ft |
| Surface Area | 3,256 acres |
| Drainage Area | 2,216 sq mi |
| Max Discharge | 16,080 cfs |
| Spillway Type | Controlled |
Ownership & Safety
| Purpose | Flood Risk Reduction |
| Owner | BUREAU OF RECLAMATION |
| Owner Type | Federal |
| Hazard Classification | High |
| Condition Assessment | Not Available |
| Last Inspection | 05/05/2021 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | ID00280 |
| Federal ID | ID00280 |
| More Info | State Dam Safety Program |