Boulder Lake, located in Valley County, Idaho, is a privately owned reservoir with a primary purpose of irrigation. The dam, a masonry structure with a multi-arch core, stands at a height of 15 feet and was completed in 1902. With a storage capacity of 1310 acre-feet and a surface area of 114 acres, Boulder Lake serves as a vital resource for the surrounding agricultural community.

The reservoir is fed by Boulder Creek, a tributary of the North Fork Payette River, and has a drainage area of 1.8 square miles. The spillway, which is uncontrolled and 480 feet wide, allows for a maximum discharge of 160 cubic feet per second. The dam's condition was last assessed as "fair" in July 2018, with a significant hazard potential and a moderate risk assessment score of 3. Despite its age, Boulder Lake continues to play a crucial role in water resource management and agricultural irrigation in the region.

Water resource and climate enthusiasts interested in the history and engineering of irrigation infrastructure will find Boulder Lake to be a fascinating case study. From its construction over a century ago to its continued operation and maintenance today, the reservoir exemplifies the intersection of human ingenuity and natural resource management. With its location in the scenic town of McCall, Idaho, Boulder Lake is not just a functional reservoir but also a reminder of the importance of sustainable water utilization in a changing climate.