Chino Ranch #1, also known as Arnold Reservoir, is a local government-owned water storage facility located in Brea, California. Built in 1918, this earth dam structure stands at a height of 22 feet and has a hydraulic height of 17.5 feet. With a storage capacity of 137 acre-feet, this reservoir primarily serves the purpose of water supply for irrigation and other needs in the area.

Managed by the California Department of Water Resources, Chino Ranch #1 is regulated, permitted, inspected, and enforced by state authorities to ensure its safety and functionality. The dam is situated along the Tonner Canyon Creek in San Bernardino County and has a significant hazard potential. Despite this, the condition assessment deemed it satisfactory as of September 2017, with regular inspections conducted to monitor its structural integrity.

The reservoir covers a surface area of 20 acres and has a maximum discharge capacity, although specific spillway details are not provided in the data. With its rich history and crucial role in water resource management, Chino Ranch #1 stands as a key infrastructure for water supply in the region, highlighting the importance of sustainable practices and climate resilience in maintaining such critical water resources.