Onion Dam, located in Humboldt County, Nevada, serves a primary purpose of irrigation along with recreational activities. This privately owned structure stands as an earth dam type with a height of 48 feet and a hydraulic height of 42 feet, providing storage capacity of 1500 acre-feet. The dam, built on the East Fork Alder Creek, has a spillway width of 30 feet and a maximum discharge of 3700 cubic feet per second, ensuring efficient water management in the region.

Managed by the Nevada Department of Water Resources, Onion Dam has a significant hazard potential but is currently assessed to be in fair condition. The last inspection in June 2019 revealed a need for regular maintenance, with an inspection frequency of every 3 years. Despite the moderate risk level associated with the dam, it meets regulatory standards and has emergency action plans prepared to ensure public safety in case of any unforeseen events. With its strategic location and functional design, Onion Dam stands as a vital water resource infrastructure supporting the agricultural and recreational needs of the surrounding community.