Vasona Percolating Reservoir Report

Last Updated: December 5, 2025

Vasona Percolating, also known as Vasona Reservoir, is a public utility water resource located in Los Gatos, California.


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Summary

This reservoir plays a crucial role in flood risk reduction, irrigation, and water supply in the region. Built in 1935, this earth dam stands at a height of 34 feet and has a hydraulic height of 22 feet, holding a storage capacity of 410 acre-feet. With a drainage area of 44.2 square miles, Vasona Percolating is situated on the Los Gatos Creek, serving as a vital water management infrastructure in Santa Clara County.

Managed by the California Department of Water Resources (DWR) under the Safety of Dams program, Vasona Percolating is regularly inspected to ensure its structural integrity and operational readiness. The dam has a high hazard potential due to its location and the surrounding urban development. Despite this, the condition assessment in 2017 deemed it satisfactory, with an inspection frequency of once per year. The emergency action plan (EAP) for the reservoir was last revised in September 2018, highlighting the proactive measures in place to address any potential risks or emergencies.

In addition to its flood risk reduction capabilities, Vasona Percolating provides essential water storage and management services for the local community. As climate change continues to impact water resources, the importance of well-maintained infrastructure like Vasona Percolating cannot be overstated. With a long history of service and a commitment to safety and regulation, this reservoir remains a critical asset in ensuring water security and resilience in Santa Clara County.

Year Completed

1935

Dam Length

1000

Dam Height

34

River Or Stream

Los Gatos Crk

Primary Dam Type

Earth

Surface Area

58

Hydraulic Height

22

Drainage Area

44.2

Nid Storage

410

Hazard Potential

High

Nid Height

34
       
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.