Big Supai Tank, located in Coconino, Arizona, is a privately owned earth dam completed in 1882 to store water from Johnson Creek. With a height of 34.4 feet and a storage capacity of 55.5 acre-feet, this historic structure serves as a vital resource in the region. Despite being unregulated by federal agencies, the Arizona Department of Water Resources oversees its permitting, inspection, and enforcement to ensure its safety and functionality.

This low-hazard dam, with a surface area of 8.6 acres and a drainage area of 2.18 square miles, plays a crucial role in water management in the area. Although not rated for its condition assessment, the dam has a high risk assessment due to its age and historical significance. Regular inspections, last conducted in October 2018, help monitor its integrity and mitigate potential risks. Its location in the scenic surroundings of S34, T22N, R1E adds to its allure for water resource and climate enthusiasts interested in the intersection of history, engineering, and natural landscapes.

As one of the oldest dams in the region, Big Supai Tank stands as a testament to early water management practices and the importance of preserving such heritage structures. Its role in storing water for agricultural and other purposes highlights the need for continued monitoring and maintenance to ensure its longevity and functionality. For enthusiasts interested in the intersection of water resources, climate, and historical infrastructure, this site offers a fascinating glimpse into the past while also raising questions about the future of water management in a changing climate.