O`Shaughnessy, also known as Hetch Hetchy Reservoir, is a gravity dam located in Moccasin, California, on the Tuolumne River. Built in 1923, this impressive structure stands at a height of 312 feet and has a storage capacity of 360,000 acre-feet. The primary purpose of this dam is to provide water supply for the region, serving as a critical source for both hydroelectric power generation and water distribution.

Managed by the local government and regulated by the California Department of Water Resources (DWR) and Safety of Dams, O`Shaughnessy Dam is considered to have a high hazard potential. However, recent inspections have deemed its condition as satisfactory. The dam plays a crucial role in water resource management in the area, with a drainage area of 459 square miles and a surface area of 1972 acres. Despite its age, O`Shaughnessy continues to operate efficiently, meeting the water needs of the surrounding communities.

With its historic significance and vital role in the local water supply infrastructure, O`Shaughnessy Dam stands as a testament to engineering excellence and resource management. As climate change continues to impact water resources, structures like O`Shaughnessy play a crucial role in ensuring a reliable water supply for both current and future generations. The dam's construction, maintenance, and regulatory oversight highlight the complex interplay between water management, climate resilience, and infrastructure development in California.