Deraeve Reservoir #1 (Lower), also known as Deraeve Lower Dam, is a privately owned earth dam located in McCoy, Oregon. Completed in 1978, this reservoir serves primarily for irrigation purposes and has a storage capacity of 325 acre-feet. Situated on the Ash Swale river, the dam stands at a height of 18 feet with a structural height of 18 feet.

With a surface area of 42.95 acres and a drainage area of 0.9 square miles, Deraeve Reservoir #1 (Lower) has a significant hazard potential and is regulated by the Oregon Water Resources Department. The dam features a slide (sluice gate) as its outlet gates and has a maximum discharge capacity of 1459 cubic feet per second. The last inspection was conducted in October 2020, with a scheduled inspection frequency of every 3 years.

Water resource and climate enthusiasts will be intrigued by the engineering design and operational aspects of Deraeve Reservoir #1 (Lower). This reservoir not only plays a crucial role in supporting irrigation activities in the region but also poses a significant risk potential that necessitates regular monitoring and maintenance. As part of the water infrastructure in Oregon, the dam serves as a vital component in managing water resources and ensuring the safety of surrounding communities in case of emergencies.