Lake Madigan Reservoir Report

Last Updated: December 5, 2025

Lake Madigan, located in Solano County, California, is a vital water supply reservoir owned and regulated by the local government.


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Summary

Built in 1908, this earth dam stands at a height of 89 feet, with a storage capacity of 1175 acre-feet. The dam serves the primary purpose of water supply for the city of Greenville, drawing from the waters of Wild Horse Creek.

With a surface area of 72 acres and a drainage area of 1.5 square miles, Lake Madigan plays a crucial role in ensuring water security for the region. Despite its age, the dam has been assessed as satisfactory in condition, with a high hazard potential. Regular inspections are conducted, with the last assessment taking place in October 2020. For water resource and climate enthusiasts, Lake Madigan is a fascinating example of sustainable water management in action, highlighting the importance of proper regulation and maintenance of critical infrastructure in the face of changing environmental conditions.

Year Completed

1908

Dam Length

665

Dam Height

89

River Or Stream

Wild Horse Creek

Primary Dam Type

Earth

Surface Area

72

Hydraulic Height

77

Drainage Area

1.5

Nid Storage

1175

Hazard Potential

High

Nid Height

89
       
Seasonal Comparison

Weather Forecast

Dam Data Reference

Condition Assessment

Satisfactory
No existing or potential dam safety deficiencies are recognized. Acceptable performance is expected under all loading conditions (static, hydrologic, seismic) in accordance with the minimum applicable state or federal regulatory criteria or tolerable risk guidelines.
Fair
No existing dam safety deficiencies are recognized for normal operating conditions. Rare or extreme hydrologic and/or seismic events may result in a dam safety deficiency. Risk may be in the range to take further action. Note: Rare or extreme event is defined by the regulatory agency based on their minimum
Poor A dam safety deficiency is recognized for normal operating conditions which may realistically occur. Remedial action is necessary. POOR may also be used when uncertainties exist as to critical analysis parameters which identify a potential dam safety deficiency. Investigations and studies are necessary.
Unsatisfactory
A dam safety deficiency is recognized that requires immediate or emergency remedial action for problem resolution.
Not Rated
The dam has not been inspected, is not under state or federal jurisdiction, or has been inspected but, for whatever reason, has not been rated.
Not Available
Dams for which the condition assessment is restricted to approved government users.

Hazard Potential Classification

High
Dams assigned the high hazard potential classification are those where failure or mis-operation will probably cause loss of human life.
Significant
Dams assigned the significant hazard potential classification are those dams where failure or mis-operation results in no probable loss of human life but can cause economic loss, environment damage, disruption of lifeline facilities, or impact other concerns. Significant hazard potential classification dams are often located in predominantly rural or agricultural areas but could be in areas with population and significant infrastructure.
Low
Dams assigned the low hazard potential classification are those where failure or mis-operation results in no probable loss of human life and low economic and/or environmental losses. Losses are principally limited to the owner's property.
Undetermined
Dams for which a downstream hazard potential has not been designated or is not provided.
Not Available
Dams for which the downstream hazard potential is restricted to approved government users.