Tules on Twitchell Island in the Delta. (Photo: Josh Cassidy/KQED)
With thousands of acres of rich farmland, the Delta has a long agricultural legacy. But farming there can be a risky business. Dozens of farms have been flooded over the past half century as aging levees have collapsed.
That became a reality for farmer Rudy Mussi on the morning of June 3, 2004. It was clear, sunny day. "You never expect a flood in the summer months," says Mussi.
Mussi was growing corn and asparagus on lower Jones Tract, an island in the Delta, 10 miles west of Stockton. That morning, he got a phone call. Water was flooding onto his farmland.
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"Your heart stops for a second or two and then realism sets in. And you just start moving your equipment and get it to high ground," says Mussi.
How did a flood happen a on a sunny day? It's because of a basic rule of physics. Mussi farmed on an island below sea level, like a lot of the islands in the Delta. The Delta used to be a huge swath of wetlands, where two major rivers met San Francisco Bay. Today, earthen levees hold that water back – most of the time.
"Once a break occurs, you know, there's no way you're gonna stop that, not with 10 feet of water on the other side," Mussi says. Draining the island and repairing the levees around Jones Tract cost about $90 million.
The levee break on Jones Tract in 2004. (Photo: CA Department of Water Resources)
It wasn't an isolated incident. Over the last century, more than 150 levees have failed in the Delta.
Delta Infrastructure at Risk
"This is how we get ourselves in kind of an arms race between the water and the land," says Jeff Mount, professor with the Center for Watershed Sciences at the University of California-Davis.
Levee-building began in the 1850s, when settlers came to the Delta for the rich soil. More than a thousand miles of levees were built. "This network of levees through time had to get bigger and bigger for a very basic reason: the land has been steadily lowering," says Mount.
As farmers exposed the rich peat soil, it started decomposing. The land level dropped; "In some places they talked about four inches per year," says Mount. Today, it's less than an inch per year thanks to better farming practices.
Add up all those inches over the past century and some islands are now 30 feet below sea level. That puts a lot of stress on the levees. There are also other concerns: rising sea levels and extreme floods. "And then the big 800-pound gorilla in the room – we're due for a very large earthquake on the San Andreas system."
Add up all these risks and Mount says there's a two-thirds chance of a catastrophic levee failure in the next 50 years. That, of course, affects farmers and communities in the Delta, but it could also impact California's water supply.
"The raindrops that fall in Mount Shasta are consumed by people in San Diego. Water moves a great distance and this is one of the critical hubs in that system," says Mount.
Fixing the Delta's levees is estimated to cost billions. But on some islands, scientists are experimenting with a new fix.
Farming Carbon
Peat soil samples on Twitchell Island. (Photo: Josh Cassidy/KQED)
On a windy day on Twitchell Island in the Delta, ecologist Lisa Windham-Myers of the US Geological Survey pushes her way through a wetland filled with a tall, reed-like plant known as tule.
"The plant grows... some of these are 16 feet tall. They're just huge," she says. That growth is changing the ground we're standing on. Windham-Myers pulls out a sample of the dark peat soil.
The wetland produces soil at a rapid rate – four inches a year on average. That's huge, says USGS scientist Brian Bergamaschi, in a place where the land is sinking. "These islands are like bowls and the way we see projects like this is you want to fill up the middle of that bowl and help level out the whole island."
Planting wetlands like this one could raise the land level and water table on the inside of levees, relieving some of the pressure. But why would farmers want to replace cash crops with tule? Windham-Myers points to the soil.
"This is basically almost 100 percent carbon. These take up far more than a typical forest environment," she says. California is setting up a market for carbon, as part of the state's effort to cut global warming emissions. Early next year, companies that need to reduce their emissions could pay farmers to store carbon in wetlands like this.
USGS scientist Brian Bergamaschi talks with Delta farmer Al Medvitch. (Photo: Josh Cassidy/KQED)
Today, two farmers are here checking out the project: Steve Mello, a Delta farmer on Tyler Island and Al Medvitch, a farmer in the Montezuma Hills.
"The potential has been demonstrated well. You guys are standing in the middle of it. But in order to move from here to market, we need to develop a lot more techniques so people can come and verify that the carbon is stored," says Brian Bergamaschi, describing how wetland farming might work.
Both farmers seem open to the idea. But Mello says ultimately, it depends on the bottom line. "It would absolutely need to cash flow. While it could dovetail with levee stability, it would still need to generate enough to amortize your property value."
Still, Mello says assuming carbon prices are high enough, growing patches of wetlands could be a feasible way to improve the levees and to stay farming.
