The Nation's Breadbasket Is Poisoning Its Own Water Supply

By Elizabeth Royte, Grist.org. Posted October 23, 2007.

In late September, the corn and soybean fields of the lower Missouri River floodplain are a lovely dull brown, nearly ready for harvest. The row crops sprawl as far as the eye can see, their regimental march broken only by levees, gravel roads, the occasional band of cottonwoods, and the endless tracks of the Burlington Northern and Santa Fe. The scenery is pastoral and soothing. But this abundance, and the security it evokes, has a darker underside. The nation's breadbasket, it turns out, is poisoning the water.

The Mississippi River basin, which includes the Missouri River, drains 1.83 million square miles east of the Rocky Mountains and provides drinking water to more than 18 million people. The river receives not only the effluent of all those humans, but also that of their crops and cows.

Of the many threats to drinking water in this region, which includes 65 percent of America's cropland, farming is by far the worst.

How It All Begins

The trouble starts with a healthy rain, which washes sediment from farms, especially from row crops like corn, into waterways. Nationwide, farms lose 1.76 billion tons of topsoil each year to wind and water. The sediment can clog intake pipes at water treatment plants, make the water cloudy, and give microbes places to hide from disinfectants.

By the time the Missouri River reaches Kansas City, for instance, its turbidity can be as high as 10,000 NTUs (nephelometric turbidity units). To serve this water to customers, the local utility must use chemicals and mechanical processes to lower turbidity to less than 0.1 NTU. They don't call it the Big Muddy for nothing.

Any municipality that delivers surface water, as opposed to groundwater, deals with turbidity. It just happens to be worse in areas where the soil is regularly disturbed (as opposed to, say, a forested watershed), and nowhere is it more disturbed than in the nation's heartland. Utilities across the country spend millions each year to meet the Environmental Protection Agency's standards for 80 different contaminants, but every municipality addresses a unique contaminant profile: a bit of industry, a bit of ag, a bit of naturally occurring arsenic or radium.

The combinations are endless. Like any utility, Kansas City Water Services treats what the river delivers. But it happens to do a better job than just about any utility in the nation. Not only does it meet and exceed federal and state standards, it does so on a daily, instead of quarterly or annual, basis.

Once you understand what's washing downstream, the feat becomes all the more impressive.

When soil runs off the land, it also sends phosphorus and nitrogen fertilizer into ditches and streams; 6 billion pounds end up in the Mississippi and its tributaries each year. In rivers and reservoirs, these nutrients encourage the growth of algae. When algae die, bacteria feast on them, and they also consume oxygen in the water. The biotic riot sluices down to the Gulf of Mexico, where it has created an oxygen-free "dead zone" that supports no marine life. In the summer of 2007, the zone expanded from 6,000 square miles to 7,500, an area nearly the size of New Jersey.

But enough about shrimp: those algae are bad news for drinking water, too. Anaerobic conditions release iron and manganese previously bound to a river or reservoir's bottom sediments, which causes the water's taste, odor, and color to quickly go downhill. To deal with skunked water, plant operators dump in chemicals like potassium permanganate or copper sulfate. Dead algae and bacteria can also combine with chlorine -- the mainstay of water disinfection since the early 20th century -- to form nasty byproducts like trihalomethanes, which have been linked to an increased risk of bladder cancer and miscarriage.

The nitrogen itself, which converts to nitrate, is also a potential health threat to humans. In babies, nitrate binds to hemoglobin in blood and hinders its ability to deliver oxygen to the brain. In adults, high nitrate levels have been linked with increased risk of hyperthyroidism, birth defects, and miscarriage. To stay under the federal nitrate limit of 10 parts per billion, the city of Des Moines, Iowa, spent $4.5 million on an ion-exchange process that switches nitrate for chloride.

"We run it fifty to a hundred times a year," Randy Beavers, assistant manager of Des Moines Water Works, says. "It costs us $3,000 a day." At peak runoff, the utility just beats the cutoff, bringing levels from as high as 20 ppb down to a yearly average of 9.9 ppb. Iowa communities that drink from shallow wells, and that lack funds for fancy ion-exchange systems, have a tougher time of it. When nitrate levels spike, they issue "blue baby" alerts: kids, step away from that faucet.

See more stories tagged with: water, pollution, farming

Elizabeth Royte is the author of Garbage Land: On the Secret Trail of Trash (Little, Brown) and the forthcoming book Bottlemania: How Water Went On Sale and Why We Bought It.

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