James H. Turner, also known as the San Antonio Reservoir, is a local government-owned water supply dam located in Sunol, California. Completed in 1964, this earth-type dam stands at a height of 193 feet and has a storage capacity of 50,500 acre-feet. Situated on the San Antonio Creek, the dam serves as a vital water resource for the surrounding communities in Alameda County.

Managed by the California Department of Water Resources (DWR) and subject to state regulations, inspections, and enforcement, James H. Turner plays a crucial role in ensuring water security for the region. With a high hazard potential but a satisfactory condition assessment as of September 2019, the dam is regularly inspected to maintain its safety standards and emergency preparedness. The dam's primary purpose is water supply, reflecting its importance in providing a reliable source of water for domestic, agricultural, and industrial needs in the area.

Despite its age, James H. Turner continues to serve as a key infrastructure for water management in California. With a designated emergency action plan and periodic risk assessments, the dam exemplifies the commitment to safeguarding water resources and mitigating potential hazards associated with its operation. As climate change impacts water availability and quality, structures like James H. Turner are essential for ensuring resilience in the face of evolving environmental challenges.