Grasmere South Dike, also known as Grasmere Reservoir Dike, is a private structure located in Owyhee, Idaho, along Rattlesnake Creek and Marys Creek. Built in 1909 for irrigation purposes, this earth dam stands at a height of 11.2 feet and has a hydraulic height of 1.8 feet, providing crucial water storage of 110.1 acre-feet. With a surface area of 213 acres and serving a drainage area of 1.3 square miles, this dam plays a vital role in supporting agricultural activities in the region.

Despite being classified as having a low hazard potential, Grasmere South Dike is regularly inspected with a fair condition assessment as of August 2020. With a high risk assessment rating of 2, it is essential for the responsible authorities to monitor and implement risk management measures to ensure the safety and functionality of this key water resource infrastructure. While the dam currently does not have a spillway, outlet gates, or locks, ongoing inspections and assessments are crucial to maintaining its integrity and mitigating any potential risks that may arise.

The presence of Grasmere South Dike highlights the importance of water resource management and infrastructure in sustaining agricultural activities in the area. As climate change continues to impact water availability and usage patterns, structures like this dam play a critical role in ensuring a reliable water supply for irrigation. With proper monitoring, maintenance, and risk management measures in place, Grasmere South Dike remains a valuable asset for water resource and climate enthusiasts in the region.