Stanley A. Mahr Reservoir, located in Olivenhain, California, is a crucial water supply infrastructure managed by a public utility. With a height of 79 feet and a capacity of 166 acre-feet, this earth dam was completed in 1981 to serve multiple purposes including flood risk reduction, irrigation, and water supply. The reservoir is situated on the Tr Encinitas Creek, covering a surface area of 8 acres with a drainage area of 0.04 square miles.

The dam's high hazard potential is closely monitored by the California Department of Water Resources (DWR) under the Safety of Dams program. Despite the satisfactory condition assessment in 2017, regular inspections are conducted to ensure its structural integrity and safety. In the event of emergencies, an Emergency Action Plan (EAP) is in place, last revised in February 2019, to guide response and coordination efforts. With its strategic location and vital role in water resource management, Stanley A. Mahr Reservoir stands as a critical asset in maintaining water security and resilience in San Diego County.