Delta Conveyance

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. But 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). As Metropolitan continues to increase local supplies and promote conservation in Southern California, modernizing the state's water delivery system to protect from future losses is the most cost effective way to manage rates for the region. 

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California’s Vulnerable, Outdated Water System 

As a water delivery system, the Delta is outdated and faces many challenges.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

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. 

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. 

Operational Flexibility

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

Affordability

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. 

“Water projects require vision, leadership, and thoughtful and deliberate decisions, because they take a long time. We have to be visionaries and advance that vision together.” 

—Gloria D. Gray, Metropolitan Board Chairwoman

The Path to Southern California’s Water Future 

Metropolitan’s mission to ensure a reliable, high-quality water supply for Southern California guides its support and investment in the Delta Conveyance Project. As the largest contractor of state water supplies, our decisions, along with those of many other local, state and federal agencies, are essential to the project’s ability to move forward. 

California Initiates Single Delta Tunnel Environmental Review 

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. The NOP initiated environmental review of the project to comply with the California Environmental Quality Act, as well as the preparation of an environmental impact report. 

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. A draft environmental impact report is expected in mid-2022.

Notice of Preparation

Delta Conveyance NOP & Public Scoping Q&A

DWR's Press Release

Message Points & Sample Letter for Scoping Process

Metropolitan Press Release on Funding Environmental Review

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. 

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Related Agencies

Californians for Water Security

Delta Conveyance Design and Construction Authority and Delta Conveyance Finance Authority

Delta Stewardship Council

Southern California Water Coalition

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.