Lake Ralphine
Lake Ralphine is an earth dam located in Sonoma County, California, built in 1882. It carries a High hazard potential classification and has a satisfactory condition assessment.
About Lake Ralphine
The primary purpose of Lake Ralphine is water supply. The dam stores water for municipal, industrial, or agricultural use, helping ensure a reliable supply for the surrounding area. The dam is owned by City Of Santa Rosa (local government). It impounds the Tr Santa Rosa Cr near Santa Rosa.
The dam stands 35 feet tall and stretches 700 feet across, creates a reservoir covering 19 acres, has a maximum storage capacity of 387 acre-feet, and collects water from a drainage area of 0 square miles. Completed in 1882, 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 06/05/2025.
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 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 | Sonoma |
| Nearest City | Santa Rosa |
| River/Stream | Tr Santa Rosa Cr |
| Coordinates | 38.45490, -122.67000 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 35 ft |
| Dam Height | 35 ft |
| Dam Length | 700 ft |
| Year Completed | 1882 (144 years old) |
Storage & Hydraulics
| NID Storage | 387 acre-ft |
| Max Storage | 387 acre-ft |
| Surface Area | 19 acres |
| Drainage Area | 0 sq mi |
Ownership & Safety
| Purpose | Water Supply |
| Owner | City of Santa Rosa |
| Owner Type | Local Government |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 06/05/2025 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | CA00882 |
| Federal ID | CA00882 |
| More Info | State Dam Safety Program |