Diederich Reservoir
Diederich Reservoir is an earth dam located in Los Angeles County, California, built in 1950. It carries a High hazard potential classification and has a satisfactory condition assessment.
About Diederich Reservoir
The primary purpose of Diederich Reservoir 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 Glendale (local government). It impounds the Offstream near Verdugo Viejo.
The dam stands 60 feet tall and stretches 100 feet across, creates a reservoir covering 7 acres, and has a maximum storage capacity of 174 acre-feet. Completed in 1950, 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 08/20/2025.
At 60 feet, this dam is taller than 95% 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 | Los Angeles |
| Nearest City | Verdugo Viejo |
| River/Stream | Offstream |
| Coordinates | 34.16900, -118.25050 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 60 ft |
| Dam Height | 60 ft |
| Dam Length | 100 ft |
| Year Completed | 1950 (76 years old) |
Storage & Hydraulics
| NID Storage | 174 acre-ft |
| Max Storage | 174 acre-ft |
| Surface Area | 7 acres |
Ownership & Safety
| Purpose | Water Supply |
| Owner | City of Glendale |
| Owner Type | Local Government |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 08/20/2025 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | CA00064 |
| Federal ID | CA00064 |
| More Info | State Dam Safety Program |