Strong Arm No 1 (Upper), also known as Treasureton Reservoir, is a private water resource located in Warm Springs, Idaho. This dam was completed in 1887 and stands at a height of 39.1 feet, with a hydraulic height of 35.8 feet. It serves multiple purposes and has a storage capacity of 1713 acre-feet, providing essential water for the surrounding area. The dam is primarily made of earth and stone, with a controlled spillway type to manage water flow.

With a hazard potential rated as high and a condition assessment of fair, Strong Arm No 1 (Upper) is regularly inspected to ensure its structural integrity. The dam has a very high risk assessment level (1) and is under the jurisdiction of the Idaho Department of Water Resources. It has a drainage area of 29.9 square miles and a normal storage capacity of 1713 acre-feet, making it a crucial water source for the region. Despite its age, the dam continues to play a vital role in managing water resources and protecting against potential hazards in the area.