San Dimas Reservoir Report

Last Updated: December 5, 2025

San Dimas, also known as San Dimas Reservoir, is a gravity dam located in La Verne, California, that serves as a crucial flood risk reduction structure along the San Dimas Creek.


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Summary

Completed in 1922, this dam stands at a height of 131 feet and has a storage capacity of 1,534 acre-feet, providing essential water supply for irrigation and other purposes. Managed by the local government, the dam is regulated and inspected by the Department of Water Resources (DWR) for safety and enforcement.

With a high hazard potential but a satisfactory condition assessment as of September 2017, San Dimas Dam undergoes regular inspections to ensure its continued functionality and structural integrity. It is equipped with emergency action plans and updated contact information to handle any potential risks or emergencies effectively. The surrounding area, covering a surface area of 36 acres and draining 15.9 square miles, benefits from the flood risk reduction provided by this vital infrastructure.

San Dimas Dam not only plays a significant role in flood risk reduction but also contributes to irrigation and water supply in the region. Its historical significance, dating back nearly a century, underscores the importance of maintaining and monitoring this structure to safeguard the local community and water resources in Los Angeles County, California.

Year Completed

1922

Dam Length

340

Dam Height

131

River Or Stream

San Dimas Creek

Primary Dam Type

Gravity

Surface Area

36

Hydraulic Height

112

Drainage Area

15.9

Nid Storage

1534

Hazard Potential

High

Nid Height

131
       
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.