Which dam near Sacramento is primarily responsible for providing water to the Central Valley?

Folsom Dam is primarily responsible for providing water to the Central Valley due to its strategic location on the American River, which is a significant source of water for the region. The dam plays a critical role in managing the water supply and flood control for the Central Valley, ensuring that agricultural and urban water needs are met. It creates Folsom Lake, which stores water and supports both environmental and recreational activities while also supplying water for irrigation and municipal use. The infrastructure and operations of Folsom Dam are designed to efficiently deliver water resources to the Central Valley, making it a vital part of California's water management system.

In contrast, the other dams cited serve different functions or are located in areas that do not directly impact the Central Valley as significantly as Folsom Dam does. Castaic Dam primarily serves the metropolitan Los Angeles area, while San Luis Dam is pivotal for managing water for the Coachella and Imperial Valleys. New Don Pedro Dam, while it does contribute water to certain regions, is not as integral to the Central Valley water supply as Folsom Dam.