French Lake Reservoir Report

Last Updated: December 5, 2025

French Lake, located in Graniteville, California, is a rockfill dam with a height of 95 feet and a hydraulic height of 89.5 feet.


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Summary

Built in 1859 for irrigation purposes, the dam has a storage capacity of 13,940 acre-feet and serves multiple functions including hydroelectric power generation, recreation, and water supply. The dam is regulated by the Federal Energy Regulatory Commission and is inspected regularly to ensure its safety and compliance with state regulations.

The dam's spillway type is uncontrolled, with a maximum discharge of 4,300 cubic feet per second. The lake has a surface area of 337 acres and drains an area of 4.9 square miles. Despite its high hazard potential, the risk assessment for the dam is moderate (3). Although the condition assessment is not available, emergency action plans are in place and regularly updated to meet guidelines. With its historical significance and important role in water resource management, French Lake is a key feature in the Nevada County landscape.

French Lake's importance extends beyond its physical attributes, serving as a testament to the ingenuity of its designers, Fred Tibbits and State Engineer. The dam stands as a reminder of the vital role that water resources play in sustaining communities and ecosystems. With its picturesque surroundings and diverse uses, French Lake is a valuable asset that continues to shape the water and climate landscape of the region.

Year Completed

1859

Dam Length

200

Dam Height

95

River Or Stream

Canyon Creek

Primary Dam Type

Rockfill

Surface Area

337

Hydraulic Height

89.5

Drainage Area

4.9

Nid Storage

13940

Structural Height

95

Hazard Potential

High

Foundations

Rock

Nid Height

95
       
Seasonal Comparison

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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.