Longeley is a privately owned irrigation dam located in Niobrara, Wyoming, along the Longely Draw river. Built in 1972 by J H Coffman, this Earth-type dam stands at a height of 22 feet and has a storage capacity of 88 acre-feet. Despite its age, the dam is in poor condition and has a low hazard potential, with a moderate risk assessment rating of 3.

The dam serves multiple purposes, including irrigation, fire protection, stock watering, small fish pond maintenance, and flood risk reduction. Its primary spillway type is uncontrolled, with a spillway width of 100 feet. Longeley is state-regulated and inspected by the Wyoming State Engineer's Office, ensuring its compliance with safety standards and enforcement measures.

Although Longeley has not undergone recent modifications or emergency action plan updates, its moderate risk assessment highlights the importance of ongoing monitoring and maintenance to ensure the safety and functionality of this vital water resource infrastructure in Wyoming.