Janes Flat Reservoir Report

Last Updated: December 5, 2025

Janes Flat, located in Modoc County, California, is a federal irrigation dam constructed in 1918 by the USDA Forest Service.


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Summary

With a height of 22 feet and a length of 785 feet, this earth dam serves multiple purposes including fire protection, stock watering, and irrigation. The dam has a controlled spillway with a width of 60 feet and a maximum discharge capacity of 780 cubic feet per second, making it an essential water resource for the region.

Despite being classified as having a significant hazard potential, Janes Flat has not been rated for its condition assessment. The dam is primarily managed by the Forest Service and is inspected every five years to ensure its safety and integrity. With a very high risk assessment rating, it is crucial for emergency preparedness and risk management measures to be in place to mitigate any potential dangers associated with the dam.

As a key water infrastructure for irrigation and other water-related activities, Janes Flat plays a vital role in supporting agriculture and wildlife in the region. Its historical significance and ongoing maintenance underscore the importance of sustainable water resource management in the face of changing climate patterns and increasing water demands.

Year Completed

1918

Dam Length

785

Dam Height

22

Primary Dam Type

Earth

Structural Height

22

Outlet Gates

Slide (sluice gate)

Hazard Potential

Significant

Nid Height

22
       
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.