Whittier Reservoir No. 4, located in Whittier, California, is a vital water supply infrastructure owned by the local government. With a dam height of 55 feet and a hydraulic height of 53 feet, this Earth type dam was completed in 1931 and has a storage capacity of 32 acre-feet. The reservoir serves the primary purpose of water supply, drawing from the Tr San Gabriel River for its source.

Despite its age, Whittier Reservoir No. 4 has been maintained in satisfactory condition, with regular inspections showing a low hazard potential. The dam is regulated by the California Department of Water Resources and adheres to state permitting, inspection, and enforcement protocols. The last inspection in March 2021 confirmed its structural integrity, ensuring the safety and reliability of its water supply function for the surrounding area.

With a surface area of 1 acre and a drainage area of 0.08 square miles, Whittier Reservoir No. 4 plays a crucial role in managing water resources in Los Angeles County. As a key component of the local water supply infrastructure, it underscores the importance of maintaining and monitoring our water resources to meet the needs of the community and mitigate the impacts of climate change on water availability.