Naz Lake Reservoir Report

Last Updated: December 5, 2025

Naz Lake, located in Napa, California, is a privately owned Earth-type dam that serves as a crucial water supply source for irrigation and domestic use in the area.


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Summary

Completed in 1955, this dam stands at a height of 29 feet and has a storage capacity of 150 acre-feet. It is regulated by the California Department of Water Resources and undergoes regular inspections to ensure its structural integrity and compliance with safety standards.

The significant hazard potential of Naz Lake highlights the importance of ongoing monitoring and maintenance to mitigate any risks associated with the dam. Despite this, the condition assessment in 2017 deemed the structure to be satisfactory, providing a sense of assurance to the community relying on its vital water storage capabilities. With a drainage area of 0.16 square miles and a maximum discharge capacity, Naz Lake plays a critical role in managing water resources and supporting agricultural activities in the region.

Overall, Naz Lake stands as a testament to the importance of sustainable water resource management and climate resilience. Its presence not only ensures access to essential water supplies but also underscores the need for effective regulatory oversight and emergency preparedness to safeguard against potential hazards and ensure the continued reliability of this essential infrastructure.

Year Completed

1955

Dam Length

795

Dam Height

29

River Or Stream

Tr Napa River

Primary Dam Type

Earth

Surface Area

20

Hydraulic Height

25.7

Drainage Area

0.16

Nid Storage

150

Hazard Potential

Significant

Nid Height

29
       
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.