Lake Combie Reservoir Report

Last Updated: December 5, 2025

Lake Combie, located in Magnolia, California, is a captivating water resource with a rich history dating back to its completion in 1928.


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Summary

This concrete dam stands at an impressive 95 feet tall, with a hydraulic height of 90 feet and a structural height reaching 100 feet. The reservoir boasts a storage capacity of 5,555 acre-feet, serving primarily for irrigation purposes while also supporting hydroelectric power generation and water supply.

Managed by the Federal Energy Regulatory Commission, Lake Combie is subject to rigorous state regulation, inspection, and enforcement to ensure its safety and efficiency. The dam spans 762 feet in length, covering a surface area of 360 acres and draining a 135.6-square-mile watershed area. With a maximum discharge capacity of 28,700 cubic feet per second and a spillway of uncontrolled type, this reservoir poses a high hazard potential while maintaining a moderate risk assessment rating.

As a key water resource in Nevada County, Lake Combie provides essential services to the local community and beyond. Its picturesque setting along the Bear River, with the involvement of notable designers like Fred Tibbits and State Engineer, adds to the allure of this hydrological gem. With its strategic location and significant storage capacity, Lake Combie remains a vital asset for irrigation, hydroelectric power, and water supply in the region, making it a must-visit destination for water resource and climate enthusiasts seeking to appreciate the intersection of engineering marvels and natural beauty.

Year Completed

1928

Dam Length

762

Dam Height

95

River Or Stream

Bear River

Primary Dam Type

Concrete

Surface Area

360

Hydraulic Height

90

Drainage Area

135.6

Nid Storage

5555

Structural Height

100

Hazard Potential

High

Foundations

Rock

Nid Height

100
       
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.