Grasmere Middle Dam, also known as Grasmere Reservoir North Middle Dam, is a privately owned structure located in Owyhee, Idaho. Completed in 1936, this earth dam stands at a height of 15.5 feet and has a hydraulic height of 12.2 feet. It plays a crucial role in water resource management, with a storage capacity of 420.2 acre-feet and a surface area of 152.9 acres.

Situated on Rattlesnake Creek and Marys Creek, Grasmere Middle Dam serves various purposes beyond water storage. Despite its poor condition assessment and low hazard potential, the dam is deemed to have a moderate risk level. With a drainage area of 1.3 square miles and a maximum discharge rate of 18 cubic feet per second, this structure is subject to state regulation, inspection, and enforcement by the Idaho Department of Water Resources.

While Grasmere Middle Dam does not have a federal owner or funding, its presence is essential for maintaining water resources in the region. The dam's uncontrolled spillway, lack of outlet gates, and poor condition warrant attention for potential risk management measures. For water resource and climate enthusiasts, understanding the role and condition of Grasmere Middle Dam is vital for ensuring the safety and sustainability of the surrounding communities and ecosystems.