The Sacramento-San Joaquin Delta is essential for the Central Valley’s economy, well-being and ecosystems. It is a major supplier of land for local agriculture, water for Central Valley farms and Bay Area and southern California cities, recreation for Californians and habitat for native species.

The Delta is ever-changing, from its origins 6,000 years ago as rising post-Ice Age sea levels drowned the confluence of local rivers to form a massive freshwater marsh. Since the 1800s this marsh was diked and drained for agriculture, leading to continuing land subsidence, as much as 25 feet below sea level in some places. Major federal and state water projects altered and reversed its water flows.