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Securing the Delta:
A Single-Tunnel Solution
The Sacramento-San Joaquin Delta is under threat, and so are the water supplies that must pass through it. With 27 million people relying on the State Water Project, the water delivery system from Northern California, it is essential that we protect this precious resource against future water instabilities such as climate change, sea level rise and earthquakes. There is a solution. At the direction of Gov. Gavin Newsom, California initiated an environmental review process for the construction of a large tunnel that would carry water from the north underneath the Delta to delivery infrastructure in the south, bypassing the Delta’s imperiled environment. Delta Conveyance Project would feature two intakes with a total diversion capacity of 6,000 cubic feet-per-second (alternatives also will be evaluated).
The Draft Environmental Impact Report was released for public review and comment in July 2022, initiating a 90-day public comment period.
California’s Vulnerable, Outdated Water System
As a water delivery system, the Delta is outdated and faces many challenges. The system relies on levees that are vulnerable to earthquakes, floods and rising sea levels under climate change. And when these levees fail, water can rush into the lower-than-sea level islands behind them, pulling in salt water from the San Francisco Bay and diminishing water quality before it can be delivered to Southern California, the Bay Area and Central Valley farmland. In addition to protecting this water supply from threats posed by climate change and earthquakes, the modernized system resulting from the Delta Conveyance Project would provide greater operational flexibility to meet multiple regulatory requirements intended to protect sensitive fish species that reside in or migrate through the Delta.
With more severe droughts and precipitation increasingly falling as rain instead of snow, the project can capture enough water during big storms to store for drier times. It also would guard against increased salinity from sea-level rise. Read DWR's fact sheet.
The Big One
A new tunnel pipeline safeguards against a major earthquake that could collapse aging Delta levees and shut off water deliveries to millions of people, farms and businesses.
A modernized system will provide greater operational flexibility to improve aquatic conditions in the Delta.
As California’s largest water source, past investments have made this water supply an affordable option.
The Highest Quality = More Local Supplies
High-quality northern Sierra water provides a necessary foundation for local supply projects, including recycling programs and replenishment of groundwater basins.
An Essential Part of the Bigger Picture
Gov. Newsom has prioritized Delta conveyance as part of the state’s Water Resilience Portfolio, a plan to ensure California has a reliable water supply for future generations in the face of climate change and other challenges. As Metropolitan diversifies our water supply by reducing future reliance on the Delta and investing in local supplies, the Delta Conveyance Project is one of many steps we must take to ensure the region’s water resiliency.
"When combined with the broader, statewide Portfolio approach, this project would help safeguard a vital source of affordable water for millions of Californians."
—DWR Director Karla Nemeth
Moving Forward: Design & Construction
The Delta Conveyance Design and Construction Authority was formed in May 2018 to help design, develop and implement the proposed Delta Conveyance program, an infrastructure project to support the resiliency of California’s freshwater supply via a proposed single-tunnel solution. Prior to project approval, this authority is supporting the planning process.