Lower Crystal Springs Reservoir Reservoir Report

Last Updated: December 14, 2025

Lower Crystal Springs Reservoir is a man-made reservoir located on the northern end of the Santa Clara Valley in California.


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Summary

The reservoir was built in 1888 to provide drinking water to the residents of San Francisco. The hydrology of the reservoir is primarily controlled by the San Andreas Fault, which runs directly under the reservoir. The reservoir is fed by surface flows from the San Mateo Creek and is also a snowpack provider during the winter months. The water from the reservoir is used for municipal purposes and agricultural irrigation. Recreational uses of the reservoir include fishing, boating, and hiking. The reservoir is home to a variety of fish species, including bass, catfish, and bluegill.

Reservoir Details

Storage 24hr Change 0.0%
Percent of Normal 100%
Minimum 42,856.0 acre-ft
2024-01-30
Maximum 65,788.0 acre-ft
2023-01-16
Average 51,463 acre-ft
Dam_Height 149
Hydraulic_Height 138.8
Drainage_Area 28.71
Year_Completed 1888
Nid_Storage 57910
Hazard_Potential High
River_Or_Stream San Mateo Creek
Surface_Area 1323
Dam_Length 600
Primary_Dam_Type Gravity
Nid_Height 149
       
Seasonal Comparison
Storage Levels
Pool Elevation Levels
Top Conserv Storage Levels
Inflow Levels

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.