Lower Crystal Springs Reservoir Report

Last Updated: December 5, 2025

Lower Crystal Springs, also known as Crystal Springs Reservoir, is a gravity dam located in San Mateo, California, along the San Mateo Creek.


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Summary

Built in 1888, this dam serves as a crucial water supply source for the region, with a storage capacity of 57,910 acre-feet and a surface area of 1,323 acres. The dam stands at a height of 149 feet, with a hydraulic height of 138.8 feet, making it an essential infrastructure for water resource management in the area.

Managed by the local government, Lower Crystal Springs is regulated and inspected by the California Department of Water Resources for safety and compliance. Despite its high hazard potential, the dam's condition assessment in 2017 deemed it satisfactory, ensuring its continued functionality and security. With a history dating back over a century, Lower Crystal Springs remains a vital component of the region's water supply infrastructure, highlighting the intersection of historical significance and modern-day climate resilience efforts.

With its proximity to San Francisco and under the jurisdiction of San Mateo County, Lower Crystal Springs plays a key role in water management and climate adaptation strategies in the region. The dam's design and construction reflect a commitment to sustainable water supply practices, while its regular inspections and emergency preparedness measures ensure the safety of surrounding communities. Lower Crystal Springs stands as a testament to the intersection of water resource management, climate resilience, and historical preservation in California's evolving landscape.

Year Completed

1888

Dam Length

600

Dam Height

149

River Or Stream

San Mateo Creek

Primary Dam Type

Gravity

Surface Area

1323

Hydraulic Height

138.8

Drainage Area

28.71

Nid Storage

57910

Hazard Potential

High

Nid Height

149
       
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.