Cogswell Reservoir, located in San Gabriel, California, is a rockfill dam completed in 1935 for the primary purpose of flood risk reduction. With a dam height of 266 feet and a storage capacity of 8,969 acre-feet, Cogswell Reservoir plays a crucial role in managing water resources in the region. Owned and regulated by the local government, the dam is also used for hydroelectric power generation, irrigation, and water supply, highlighting its versatility and importance in the area.

Despite its satisfactory condition assessment and high hazard potential, Cogswell Reservoir undergoes regular inspections and enforcement to ensure its safety and reliability. The dam is state-regulated and permitted, with a history of meeting guidelines and maintaining emergency preparedness. With the Wfk San Gabriel River flowing through its vicinity, Cogswell Reservoir serves as a vital infrastructure for water management and climate resilience in Los Angeles County. As a significant feature in the region's water landscape, Cogswell Reservoir underscores the intersection of water resource management and environmental stewardship.