Long Lake Reservoir Report

Last Updated: December 5, 2025

Long Lake, located in Graeagle, California, is a privately owned reservoir on Gray Eagle Creek with a primary purpose of water supply for irrigation and other uses.


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Summary

The dam, completed in 1938, is a rockfill structure standing at 12 feet high and holding a storage capacity of 1478 acre-feet. With a surface area of 141 acres and a drainage area of 1.13 square miles, Long Lake provides essential water resources for the surrounding area.

Managed by the California Department of Water Resources (DWR) under the Safety of Dams program, Long Lake is regulated, permitted, inspected, and enforced to ensure its structural integrity and safety. The dam is classified as having a significant hazard potential but is currently assessed as being in satisfactory condition as of September 2017. The last inspection in October 2020 indicated that the dam meets guidelines and emergency preparedness measures are in place.

Water resource and climate enthusiasts visiting Long Lake can appreciate the engineering feat of the rockfill dam, the serene beauty of the reservoir, and the vital role it plays in providing water for irrigation and other needs in the Plumas County area. As a well-regulated and maintained water source, Long Lake is a testament to the importance of sustainable water management practices in the face of changing environmental conditions.

Year Completed

1938

Dam Length

110

Dam Height

12

River Or Stream

Gray Eagle Creek

Primary Dam Type

Rockfill

Surface Area

141

Hydraulic Height

9

Drainage Area

1.13

Nid Storage

1478

Hazard Potential

Significant

Nid Height

12
       
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.