Mauvaise Terre Lake Dam
Mauvaise Terre Lake Dam is an earth dam located in Morgan County, Illinois, built in 1923. It carries a High hazard potential classification.
About Mauvaise Terre Lake Dam
The primary purpose of Mauvaise Terre Lake Dam is recreation. The dam creates a reservoir used for recreational activities such as fishing, boating, and swimming. The dam is owned by City Of Jacksonville (local government). It impounds the Mauvaise Terre Creek near Jacksonville.
The dam stands 30 feet tall and stretches 850 feet across, creates a reservoir covering 262 acres, has a maximum storage capacity of 5,624 acre-feet, and collects water from a drainage area of 34 square miles. Completed in 1923, 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 08/15/2025.
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 Illinois 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 | Illinois |
| County | Morgan |
| Nearest City | Jacksonville |
| River/Stream | Mauvaise Terre Creek |
| Coordinates | 39.71881, -90.21702 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 30 ft |
| Dam Height | 30 ft |
| Dam Length | 850 ft |
| Year Completed | 1923 (103 years old) |
Storage & Hydraulics
| NID Storage | 5,624 acre-ft |
| Max Storage | 5,624 acre-ft |
| Normal Storage | 628 acre-ft |
| Surface Area | 262 acres |
| Drainage Area | 34 sq mi |
| Max Discharge | 25,539 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Recreation |
| Owner | CITY OF JACKSONVILLE |
| Owner Type | Local Government |
| Hazard Classification | High |
| Condition Assessment | Not Available |
| Last Inspection | 08/15/2025 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | IL00709 |
| Federal ID | IL00709 |
| More Info | State Dam Safety Program |