Modesto Reservoir
Modesto Reservoir is an earth dam located in Stanislaus County, California, built in 1911. It carries a High hazard potential classification and has a satisfactory condition assessment.
About Modesto Reservoir
The primary purpose of Modesto 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 Modesto Irrigation District (public utility). It impounds the Tr Tuolumne Rv near Waterford.
The dam stands 36 feet tall and stretches 1,235 feet across, creates a reservoir covering 3,800 acres, has a maximum storage capacity of 40,000 acre-feet, and collects water from a drainage area of 10 square miles. Completed in 1911, 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 10/30/2025.
At 36 feet, this dam is taller than 83% 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 | Stanislaus |
| Nearest City | Waterford |
| River/Stream | Tr Tuolumne Rv |
| Coordinates | 37.66200, -120.68070 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 36 ft |
| Dam Height | 36 ft |
| Dam Length | 1,235 ft |
| Year Completed | 1911 (115 years old) |
Storage & Hydraulics
| NID Storage | 40,000 acre-ft |
| Max Storage | 40,000 acre-ft |
| Surface Area | 3,800 acres |
| Drainage Area | 10 sq mi |
Ownership & Safety
| Purpose | Water Supply |
| Owner | Modesto Irrigation District |
| Owner Type | Public Utility |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 10/30/2025 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | CA00243 |
| Federal ID | CA00243 |
| More Info | State Dam Safety Program |