Cinnabar, also known as Swain Number Two, is a privately owned irrigation dam located in Weiser, Idaho. Built in 1975, this earth dam stands at a height of 26 feet and has a hydraulic height of 21.5 feet. With a storage capacity of 173 acre-feet and a surface area of 22 acres, Cinnabar plays a crucial role in providing water for agricultural purposes in the area.

Managed by the Idaho Department of Water Resources, Cinnabar is regulated, permitted, inspected, and enforced to ensure its safe operation. The dam has a low hazard potential and is currently assessed to be in fair condition. With a moderate risk level, measures for risk management are in place to address any potential issues that may arise. In the event of an emergency, protocols are in place to ensure that appropriate action can be taken swiftly and effectively.

Situated on unnamed streams and Cove Creek in Washington County, Cinnabar serves as a key infrastructure for water resource management in the region. With its controlled spillway and moderate risk assessment, the dam continues to support the irrigation needs of the local community while maintaining a focus on safety and environmental responsibility.