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California's sinking delta

Efforts are under way to reverse the deterioration of a major water source, the Sacramento-San Joaquin Delta in California, which is sinking.

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Guus Borger, a Dutch historian at the University of Amsterdam, helped unearth this truth. He discovered 16th-century government documents indicating that low-lying areas were once devoted to farming wheat, a crop that would require lands much higher than these areas are today. That revelation led to a series of discoveries, and to a new account of how the Dutch created the modern Netherlands.

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Before settlement, the country comprised an expanse of dome-shaped peat bogs rising above sea level. Around 1200, farmers dug channels to drain the domes, and the land sank, setting off a centuries-long race between technology and water. As sinking land and higher water tables threatened crops, the Dutch found better ways to drain the land – sluices, followed by dikes and windmill-powered pumps – and this lowered the water table further, enabling oxygen and microbes to penetrate deeper, devour more peat, and deflate additional land.

Today’s Netherlands lies up to 20 feet below sea level and gushes millions of tons of peat-derived carbon into the air each year.

Back in California, a patch of lush green sits in the middle of Twitchell Island – 15 acres of restored wetlands bristling with seven-foot tule and cattails. Robin Miller and Roger Fujii of the US Geological Survey in Sacramento hope to use the same plants that built the delta’s islands over thousands of years to build it once again.

This experimental plot, started in 1997, has packed away an inch and a half of organic detritus per year. “It surprises even us,” says Dr. Miller. “You could bring an island as deeply ... subsided as Twitchell up to tidal range in 100 years if you wanted to.” In a similar experiment on Sherman Island, rice is being farmed on flooded fields to accumulate carbon.

Even if a levee breaks after just 20 years, such strategies would reduce the volume of water “gulped” by the island, and therefore reduce the chance of catastrophe.

But scientists looking for solutions face an uphill battle. California’s financial crisis has prevented enlarging projects such as Miller’s experimental plot. Government proposals have generally favored strategies that route fresh water around the delta to protect it from the “big gulp” rather than addressing subsidence itself. And California makes money off the delta as it stands now, by leasing islands to farmers.

But Baldocchi expects that life on the delta will change one way or another. “It just gets to the point,” he says, “that you can’t continue the same as you’ve done [simply] because it’s romantic and it’s a nice lifestyle.”

Editor’s note: For more articles about the environment, see the Monitor’s main environment page, which offers information on many environment topics. Also, check out our Bright Green blog archive and our RSS feed.