Delta Conveyance

Delta Conveyance Aerial

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.

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California’s Vulnerable, Outdated Water System  

As a water delivery system, the Delta is outdated and faces many challenges.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. 

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Climate Change

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.

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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. 

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Operational Flexibility

A modernized system will provide greater operational flexibility to improve aquatic conditions in the Delta. 

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As California’s largest water source, past investments have made this water supply an affordable option. 

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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. 

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The Draft Environmental Impact Report  

In January 2020, the California Department of Water Resources released a Notice of Preparation for a proposed project to modernize the water delivery system in the Sacramento-San Joaquin Delta. 

In December 2020, Metropolitan's board voted unanimously to fund Metropolitan's share of the environmental planning and pre-construction costs, joining other State Water Contractors. 

In July 2022, the Draft EIR was released for a 90-day public comment period.  This report evaluates and identifies potential environmental impacts of the proposed project and alternatives.  The final report is scheduled to be released in fall 2023.  Learn more about the Draft EIR

California Aqueduct

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

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The Delta Conveyance Project: Why We Need to Modernize Water Infrastructure Now

California Department of Water Resources Director Karla Nemeth speaks about the urgent need to modernize State Water Project infrastructure in the Sacramento-San Joaquin Delta.

Delta Conveyance: A Proposal to Protect Water Supplies for the Future

El Proyecto de Transporte de Agua por Tunel Único en el Delta