Sommerville, also known as Star Reservoir, is a privately owned water storage structure located in Owyhee, Idaho. Built in 1926, this earth dam stands at a height of 28.7 feet and has a normal storage capacity of 550 acre-feet. It is regulated by the Idaho Department of Water Resources and undergoes regular inspections to ensure its structural integrity.

The reservoir, situated on North Fork Castle Creek and Deep Creek, covers a surface area of 50 acres and serves multiple purposes, although its primary function is classified as 'Other'. With a low hazard potential and fair condition assessment, Sommerville poses a moderate risk level of 3 out of 5. Despite its age, the dam continues to be a vital water resource for the surrounding area, supporting local agricultural and ecological needs.

Managed by private owners, Sommerville operates with state oversight and is equipped with an uncontrolled spillway with a width of 14 feet. Its risk management measures are in place to mitigate potential hazards and ensure the safety of the community. As a historical landmark in the region, this dam remains an essential component of water resource management in Idaho's Owyhee County.