Hay Lake, located in Harney, Oregon, is a privately owned irrigation reservoir with a dam constructed in 1905. The primary purpose of the dam is to provide water for irrigation, with a storage capacity of 200 acre-feet and a surface area of 133.6 acres. The dam is classified as an earth dam with a height of 10 feet and a hydraulic height of 8 feet, serving the drainage area of 23.7 square miles.

Despite being over a century old, Hay Lake Dam has a low hazard potential and has not been rated in terms of its condition assessment. The dam features a Needle outlet gate and has not undergone any significant modifications in recent years. The last inspection of the dam took place in 1960, with an inspection frequency of every 6 years. The dam is regulated by the Oregon Water Resources Department, with permitting, inspection, and enforcement responsibilities falling under state jurisdiction.

Overall, Hay Lake serves as a vital resource for irrigation in the region, with its modest size and low hazard potential making it a relatively low-risk structure. As a privately owned reservoir, it plays a crucial role in supporting agricultural activities in the area. With ongoing state regulation and inspections, Hay Lake Dam continues to fulfill its intended purpose of water storage for irrigation while maintaining a safe and stable condition for the surrounding environment.