Thompson Creek Reservoir Report

Last Updated: December 5, 2025

Thompson Creek, a crucial water resource in Los Angeles, California, is a local government-owned dam constructed in 1928 for flood risk reduction along the Thompson Creek river.


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Summary

With a height of 66 feet and a storage capacity of 543 acre-feet, this earth dam plays a significant role in managing water levels and protecting the surrounding areas from potential flooding. Located in Claremont, the dam is regulated and inspected by the Department of Water Resources (DWR) for its safety and operational efficiency.

Despite its age, Thompson Creek Dam has been assessed as satisfactory in condition, with a high hazard potential due to its critical role in flood risk management. The dam's satisfactory condition reflects ongoing maintenance and regulation by state agencies, ensuring its reliability in safeguarding the local community from potential water-related disasters. As a key component in water supply and flood control, Thompson Creek Dam stands as a testament to effective water resource management in Southern California, underlining the importance of infrastructure in mitigating the impacts of climate change on water resources.

Thompson Creek Dam's strategic location and purpose make it a vital asset in the region's water management infrastructure. With a comprehensive inspection and emergency preparedness program in place, the dam remains a reliable structure in addressing the challenges posed by climate change and increasing water demand. As water resource and climate enthusiasts, understanding the significance of dams like Thompson Creek in promoting water security and resilience against environmental threats is crucial for sustainable water management practices in the face of a changing climate.

Year Completed

1928

Dam Length

1500

Dam Height

66

River Or Stream

Thompson Creek

Primary Dam Type

Earth

Surface Area

345

Hydraulic Height

52.3

Drainage Area

3.46

Nid Storage

543

Hazard Potential

High

Nid Height

66
       
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.