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Field to tap: The impact of farm runoff on drinking water

It doesn’t come as a major surprise that agricultural runoff is doing more harm than good to the environment. Agriculture is the nation’s leading cause of impaired water quality, according to the U.S. Environmental Protection Agency. Storms move pesticides, nutrients and sediment from farmers’ fields to nearby waterways. These will ultimately end up in the Gulf of Mexico where they can threaten aquatic life.

But what about the impact of farm runoff on our drinking water?

Ag runoff feeds into lakes and rivers that hundreds of towns draw their water from. For example, herbicide runoff from a farm in Centralia, Mo., might end up in Goodwater Creek, which empties into the Salt River, which then flows into Mark Twain Lake. That lake provides drinking water for 70,000 residents. Water treatment plants spend millions on chemicals to clean up that surface water.

In Stoutsville, Mo., the Clarence Cannon Wholesale Water Commission treats 1.5 billion gallons of water each year. During a recent visit to its treatment plant, the commission’s general manager, Mark McNally, pointed out a massive bag of fine black powder being funneled into untreated water.

“That's 900 pounds of powdered activated carbon and that actually gets transferred over here and that is basically metered into the water,” McNally said.

The plant uses the powdered activated carbon, or PAC, to remove atrazine, an herbicide widely applied to cornfields in the spring. The PAC alone costs roughly $130,000 a year, a bill the plant has to pass onto customers.

“Aunt Agnes, you know, on Third Street has to pay more for her water because we have to recoup our money,” McNally said. “I mean we’re not in the business to make money. But we can’t go broke.”

In Iowa’s Raccoon and Des Moines Rivers, record-high levels of nitrate runoff this year are making it extremely difficult to meet the demand for clean drinking water. The general manager of Des Moines Water Works, Bill Stowe, told me he fears this will lead to damaging long-term effects.

“Our concern obviously is that once you shake customers’ faith in the safety of tap waters, you turn them to other sources like bottled water, which is … certainly a competitor,” Stowe said. “It changes our business model and puts us at risk in the long term as a viable utility for providing drinking water for a half million people.”

Are you worried about farm runoff in your drinking water? Let us know what you think by leaving a comment below.

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