Lakeside, also known as Rainbow Lake, is a private water resource located in Navajo County, Arizona. Constructed in 1904 by the USDA NRCS, this rockfill dam serves primarily for irrigation purposes, with additional benefits for recreation. The dam stands at a height of 21 feet, with a storage capacity of 2,226 acre-feet and a surface area of 118 acres, drawing water from the Show Low Creek.

Managed under the jurisdiction of the Arizona Department of Water Resources, Lakeside is subject to state regulations for permitting, inspection, and enforcement to ensure its structural integrity and safe operation. Despite its significant hazard potential, the dam's condition assessment in 2016 deemed it satisfactory, with a moderate risk rating. The surrounding area, including the city of Show Low, benefits from the water supply and recreational opportunities provided by Lakeside, making it a vital asset for both the local community and the environment.

Overall, Lakeside is a key feature in the water resource infrastructure of Arizona, showcasing the collaboration between private ownership, government agencies, and conservation efforts. With its historical significance, functional design, and ongoing maintenance, Lakeside remains a valuable resource for irrigation, recreation, and water management in the region.