Milliken Reservoir Report

Last Updated: December 5, 2025

Located in Napa, California, Milliken Reservoir, also known as Milliken, is a stunning arch dam built in 1924 primarily for water supply purposes.


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Summary

With a height of 110 feet and a length of 647 feet, this reservoir boasts a storage capacity of 1980 acre-feet and covers a surface area of 44 acres. The dam stands tall on the Milliken Creek, showcasing its crucial role in water resource management in the region.

Managed by the local government and regulated by the Department of Water Resources and Safety of Dams, Milliken Reservoir is a vital component of the water infrastructure in California. Despite its age, the dam has been deemed to be in satisfactory condition, with a high hazard potential. Regular inspections ensure its safety and the implementation of risk management measures to mitigate any potential threats. With its picturesque location and impressive engineering, Milliken Reservoir continues to play a significant role in providing water supply to the surrounding areas.

As climate change impacts water resources, the importance of maintaining and monitoring dams like Milliken becomes increasingly crucial. With its historical significance and functional importance, Milliken Reservoir stands as a testament to the ingenuity of early water management systems in California. As water resource and climate enthusiasts explore the intersection of infrastructure and environmental stewardship, Milliken Reservoir remains a site of interest and admiration for its role in sustaining vital water supplies in the region.

Year Completed

1924

Dam Length

647

Dam Height

110

River Or Stream

Milliken Creek

Primary Dam Type

Arch

Surface Area

44

Hydraulic Height

110

Drainage Area

9.3

Nid Storage

1980

Hazard Potential

High

Nid Height

110
       
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.