Monticello Reservoir Report

Last Updated: December 5, 2025

Monticello, also known as Lake Berryessa, is a Federal-owned water resource located in Napa, California.


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Summary

Constructed in 1957 by the Bureau of Reclamation, Monticello serves primarily for irrigation purposes and water supply. The dam, standing at a height of 255 feet, holds a maximum storage capacity of 1,854,819 acre-feet, with a normal storage capacity of 1,602,278 acre-feet.

With a surface area of 20,240 acres and a drainage area of 576 square miles, Monticello plays a crucial role in managing water resources in the region. The dam utilizes an uncontrolled spillway type with a width of 67 feet. The facility has a high hazard potential and undergoes regular inspections by the Bureau of Reclamation to ensure its structural integrity and safety. Despite its age, Monticello continues to be a vital asset for irrigation and water supply needs in the area.

Situated along Putah Creek, Monticello offers a picturesque setting for water resource and climate enthusiasts to explore. With its impressive architectural design and significant storage capacity, Monticello stands as a testament to the ingenuity and importance of water infrastructure in California. As a key component of the region's water management system, Monticello plays a critical role in sustaining agricultural activities and ensuring a reliable water supply for the surrounding communities.

Year Completed

1957

Dam Length

1023

Dam Height

255

River Or Stream

PUTAH CREEK

Primary Dam Type

Concrete

Surface Area

20240

Hydraulic Height

239

Drainage Area

576

Nid Storage

1854819

Structural Height

304

Hazard Potential

High

Nid Height

304
       
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.