Would water tunnel destroy California’s delta?
HOOD, Calif. — In the heart of California, at the place where two great rivers converge beneath the Tule fog, lies the linchpin of one of the largest water supply systems in the world.
Here in the Sacramento-san Joaquin River Delta, birds soar the Pacific Flyway, cows graze beside sodden rice fields and red reeds poke from still depths. In winter and spring, when the snow melts and the rain pours, water rushes through its sloughs and streams, winding around more than 200 small islands on a path to the Golden Gate and, eventually, the Pacific Ocean.
This 1,100-square-mile estuary drains a vast watershed, bringing together about half of all river flows in the state and contributing to the supplies of three out of every five Californians.
But the idyllic marsh is also the site of a bitter, decades-long battle over a proposed plan known as the Delta Conveyance Project — a 45-mile tunnel that would run beneath the delta to move more water from Northern California to thirsty cities to the south.
State officials say the tunnel is a critical piece of infrastructure that would help protect millions of Californians from losing water supplies in the event of a major earthquake or levee break. They say the project would also enable more water to be captured in wet years, girding the system against increasingly erratic and unpredictable weather made worse by climate change.
“Fixing the conveyance issues in the delta and reducing those vulnerabilities — either a catastrophic outage or more flashy hydrology — is an essential part of what will keep California, and our water infrastructure, climate-ready into the future,” said Karla Nemeth, director of the California Department of Water Resources.
Opponents say the tunnel is a boondoggle that would further imperil the delta’s fragile ecosystem, which has already been eroded by heavy water withdrawals for agriculture and cities. By diverting more water that would otherwise pass through the delta, they say, the tunnel would increase the estuary’s salinity, worsen water quality, contribute to harmful algal blooms and threaten endangered species such as delta smelt and winter-run chinook salmon.
“The operation would be a very fast death blow to the delta because it would change the hydrology, the natural hydrology, so significantly,” said Barbara Barrigan-parrilla, executive director of the group Restore the Delta.
Today, the Delta Conveyance Project
is a key component of Gov. Gavin Newsom’s strategy for a hotter, drier California, which predicts that the state may lose as much as 10% of its water supply by 2040.
Iterations of the project have been floating around since at least the 1980s, when Gov. Jerry Brown championed a so-called Peripheral Canal that would skirt water around the delta for use by the State Water Project — the vast network of canals, reservoirs and pipelines that delivers water from Northern California to farmlands and cities to the south.
The Peripheral Canal concept died at the ballot box in 1982, but the idea was later rekindled by Gov. Arnold Schwarzenegger and during Brown’s second administration in the 2010s, when it morphed from a canal to a set of twin tunnels known as the California Water Fix. It, too, failed to gain voter support.
Newsom in 2022 officially downsized the concept from two tunnels to one, rebranding it, again, as the Delta Conveyance Project. In December, the DWR released its final environmental impact report and stamp of approval for the $16 billion project, moving it perhaps closer than ever to becoming a reality.
But whether the tunnel is ultimately built depends on gaining enough support among local water suppliers and the public. Opponents are also trying to block the project in the courts.
On a recent tour of the area, officials in Newsom’s administration said the new design is more efficient and economical than its predecessors and will have fewer environmental impacts.
The preferred plan would begin with two intake valves along the Sacramento River near the community of Hood, about 15 miles south of the capital. Both intakes would operate at a maximum of 3,000 cubic feet per second, pumping water through fine fish screens and into the tunnel for transport south.
The 45-mile tunnel would run largely parallel to Interstate 5 before cutting west toward Bethany Reservoir, where it would connect with the California Aqueduct. It would have an internal diameter of about 36 feet and be buried at a depth of about 140 to 170 feet — where construction crews would bore through alluvium, sand, silt, clay and gravel beneath the soft soil and peat deposits along the marshy surface.
If completed, it would be one of the longest water tunnels in the world, and the state’s second-largest infrastructure project, behind the high-speed rail line. The project would be user funded, meaning participating state water contractors who receive the water would need to buy in. The $16 billion price tag hasn’t been updated since 2020 and will likely increase after another analysis this year, officials said.
Graham Bradner, executive director of the Delta Conveyance Design and Construction Authority, said he sees the tunnel as critical to California’s water future. Had it been completed in the winter of 2021-22, the state could have captured an additional 236,000 acre-feet of water, he said. (An acre-foot is about 326,000 gallons — or enough to supply up to three households for a year.)
The gain would have allowed the doubling of that year’s allocation to the 29 agencies that depend on the State Water Project, which together supply about 27 million residents, Bradner said. Instead, the 2022 allocation was a scant 5%, which triggered significant cuts and calls for conservation, including the strictest-ever water restrictions for people in and around Los Angeles.
In 2023, the tunnel would