Rancho Cielito, also known as Lake Los Serranos, is a privately owned dam located in San Bernardino, California, specifically in the city of Los Serranos. Built in 1912, this earth dam stands at a height of 9 feet and has a hydraulic height of 6.9 feet. Its primary purpose is for water supply, serving irrigation and domestic water needs in the area. The dam has a storage capacity of 110 acre-feet and a surface area of 25 acres, with a drainage area of 0.8 square miles.

Managed by the California Department of Water Resources (DWR) under the Safety of Dams program, Rancho Cielito is regulated, permitted, inspected, and enforced by the state authorities. Its last inspection took place in March 2021, with a hazard potential rated as high but a satisfactory condition assessment as of September 2017. Despite being privately owned, the dam plays a crucial role in water resource management and climate resilience in the region, showcasing the importance of maintaining and monitoring such structures for the safety and security of communities dependent on them for water supply.

With a rich history dating back over a century, Rancho Cielito continues to be a vital component of the local water infrastructure, ensuring a reliable water supply for agricultural and residential purposes in the surrounding area. As climate change impacts water resources, dams like Rancho Cielito play a critical role in water management and flood control. By adhering to state regulations and regular inspections, this dam remains a key asset in safeguarding against potential hazards and supporting sustainable water practices for the community it serves.