Rice crop projected to protect levees

Truth About Trade and Technology 17 August 2005

Matt Weiser , Bee Staff Writer

In the Sacramento-San Joaquin Delta, wet is for rivers and canals. Dry is for islands and levees.
So it comes as no surprise that rice has never figured very big in Delta agriculture. It just seemed wrong to plant a crop that grows in standing water on islands originally created to hold back floods.

But a new study is finding that rice may have numerous benefits for the Delta. And not just for farmers, but for the entire state.

The water draining off rice fields, it turns out, is cleaner than water from the vegetable crops that are more common in the Delta. That's important, because Delta water serves 22 million Californians.

And because rice is grown in water, it may halt subsidence, in which conventional farming slowly erodes island soils. Subsidence lowers the elevation of island interiors and increases stress on surrounding levees.

"The soil stays flooded pretty much all year, except for a few months in spring and fall," said Steve Deverel of the Davis consulting firm HydroFocus Inc., which is leading the study. "The hope is that rice can stop subsidence."

Delta soils are composed of peat, an amalgam of plant matter that piled up over millennia. When exposed to air, peat decomposes.

This process began in the 1860s, when the first major Delta levees were scraped out of the Central Valley 's native wetlands.

Conventional row-crop farming aggravates the problem, because constant plowing and watering cycles stir up the soil and expose more of it to oxidation.

As peat decomposes, island interiors sink. In some locations, this happens at a rate of up to 2 inches per year. Some islands are now more than 20 feet below sea level.

Research last year by Jeffrey Mount, a geologist at UC Davis, suggests the Delta is not sustainable in this form.

Together with rising sea levels caused by global warming and the potential for earthquakes, Mount predicted a 60 percent chance for multiple levee failures within 50 years.

Flooded islands can draw salinity in from San Francisco Bay and trap it near municipal water intakes, degrading water quality for millions of Californians. This would be disastrous to the state's farm economy and to water supplies.

Mount said neither rice growing nor any other land management tool will solve the subsidence problem. But he said rice could help manage flood risks.

"The damage in the Delta has already been done and has led to its current unstable condition," Mount said via e-mail. As a result, he said, rice "is not a silver-bullet solution, but part of a comprehensive strategy."

This is also why the Contra Costa Water District is a chief partner in Deverel's work.

The district provides drinking water to a half-million East Bay residents from two Delta intakes. That supply is harmed by organic carbon in the water running off Delta farms, another result of decomposing peat and the primary focus of the study.

By manipulating irrigation methods, the study is finding, rice fields may greatly reduce the amount of organic carbon in farm runoff.

"I think it's promising," said Dave Briggs, the district's special projects manager. "It's sort of another arrow in our quiver to improve water quality."

The $900,000 study began in 2004 and continues into 2006. The funding comes primarily from the state Water Resources Control Board.

Some of that money helped three Delta farmers convert their crops from corn to rice. One of them, Gene Muzio, said rice has been a winner for him. He has 650 acres in rice on Wright-Elmwood Tract near Stockton , with 100 acres devoted to the study.

Muzio said he uses less water and fewer chemicals and man-hours to grow rice, compared to corn.

"It's working out real good," said Muzio, who has had inquiries from neighboring farmers who want to switch to rice. "There's less water demand, less work, you make more money, and there's no straw you have to get rid of.

"The Delta is disappearing," he added. "It goes down a little bit every year, and I'll do anything to help clean up the river."

Another key benefit of the crop is that the flooded fields provide valuable wildlife habitat, especially for waterfowl. The California Rice Commission has found that 235 wildlife species use rice fields.

California is the nation's second-biggest rice producer, behind Arkansas , and 95 percent of the state's crop is grown in the valleys north of Sacramento .

The Delta, however, has been known mostly for its corn, tomatoes, asparagus and wine grapes.

One factor contributing to the study's success is a new rice variety, developed by the Rice Commission, that can tolerate the Delta's cooler temperatures, said Tim Johnson, the commission's president.

Deverel said the study is not examining subsidence specifically, but he hopes to research that aspect of rice-growing in the future.

But he said rice may replicate the ancient process that produced the Delta's peat soils originally. It prevents the soil from being exposed to air, and the rice stubble is left in the field to decompose after harvest.

"You really get multiple benefits from this project," said Sam Harader, environmental program manager for the CalFed Bay-Delta Authority. He said a change could maintain productivity and address "a lot of issues."

Curt Schmutte, principal engineer for the state Department of Water Resources, said the department is considering switching to rice on Sherman and Twitchell islands, two state-owned islands that are leased for farming in the West Delta.

"In certain locations, it does look promising as a means to mitigate the effects of farming on Delta subsidence," Schmutte said.