Mariposa Dam
Mariposa Dam is an earth dam located in Mariposa County, California, built in 1948. It carries a High hazard potential classification.
About Mariposa Dam
The primary purpose of Mariposa 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 Usace - Sacramento District (federal). It impounds the Mariposa Creek near Le Grand.
The dam stands 88 feet tall and stretches 1,330 feet across, creates a reservoir covering 510 acres, has a maximum storage capacity of 21,500 acre-feet, and collects water from a drainage area of 107 square miles. Completed in 1948, 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. An emergency action plan is in place for this dam. The most recent inspection on record was 03/22/2023.
At 88 feet, this dam is taller than 97% 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 California 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 | California |
| County | Mariposa |
| Nearest City | Le Grand |
| River/Stream | Mariposa Creek |
| Coordinates | 37.29118, -120.14789 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 88 ft |
| Dam Length | 1,330 ft |
| Year Completed | 1948 (78 years old) |
Storage & Hydraulics
| NID Storage | 21,500 acre-ft |
| Max Storage | 21,500 acre-ft |
| Normal Storage | 4,300 acre-ft |
| Surface Area | 510 acres |
| Drainage Area | 107 sq mi |
| Max Discharge | 30,000 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Flood Risk Reduction |
| Owner | USACE - Sacramento District |
| Owner Type | Federal |
| Hazard Classification | High |
| Condition Assessment | Not Available |
| Last Inspection | 03/22/2023 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | CA10107 |
| Federal ID | CA10107 |
| More Info | State Dam Safety Program |