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Iowa's biggest city is confronting the farms that surround it over water pollution. The Des Moines Water Works has announced it will sue three neighboring counties, claiming the counties are letting fertilizer runoff contaminate the drinking water in Des Moines. It is a novel attempt to control water pollution from farms, something that has been largely unregulated. NPR's Dan Charles reports.
DAN CHARLES, BYLINE: The city of Des Moines gets its water from two rivers - the Raccoon River and the Des Moines - and those rivers have a problem. Bill Stowe, general manager of the Des Moines Water Works, told Iowa Public Radio that the water often violates legal limits for a pollutant called nitrate.
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BILL STOWE: We're still seeing the public water supply in central Iowa directly risked by high nitrate concentrations.
CHARLES: Too much nitrate can be a health risk, especially for infants just a few months old, and it costs a lot of money to remove. Filtering out nitrate cost the Des Moines Water Works almost a million dollars in 2013. And Stowe says we know where a lot of this nitrate is coming from.
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STOWE: We've been in northern Iowa with our lab personnel testing water.
CHARLES: The problem comes from farms, he says. Farmers spread nitrogen fertilizer on their cornfields, it turns into nitrate and then it often runs into streams through networks of underground tile pipes that drain the soil. Those drainage systems are managed in some cases by county governments.
STOWE: When they build these artificial drainage districts that take water quickly into the Raccoon River - polluted water - they have a responsibility to us and others as downstream users.
CHARLES: Stowe's agency announced last week it intends to sue three upstream counties that manage those drainage systems.
STOWE: We need to get now down to specific improvements that they're willing to make. If they're not willing to make that, we'll see them in federal court.
CHARLES: Fertilizer runoff affects a lot more than just drinking water. It's been killing off webs of aquatic life from small Midwestern lakes to the Gulf of Mexico. And lots of programs have been set up to try to solve the problem. Scientists have created tools to help farmers minimize their use of fertilizer. John Downing, an ecologist at Iowa State University, says farmers can also build sediment-trapping ponds or create wetlands to capture water from those drainage systems. That can be costly, though.
JOHN DOWNING: You'd have to take land out of production. And if you look at the prices of land in agricultural production areas, it's very pricy.
CHARLES: So state and federal governments have been offering financial incentives, paying farmers to build those pollution traps on their land. Dan Hanrahan, a farmer in Madison County, Iowa, who's on a local committee that reviews soil and water conservation projects, says these programs are popular.
DAN HANRAHAN: We've got over a two-year waiting list of people wanting to put practices in place.
CHARLES: He says these cooperative, voluntary efforts have accomplished more than litigation ever will. Yet the problem of nitrate pollution has not gone away. And the Des Moines Water Works is saying it's time to take a harder line. Dan Charles, NPR News.