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How to Protect Water Supply from Agricultural Pollutants with Des Moines Water Works

Audio by: Wangyuxuan Xu | Writing by: Marie Hogan, Amanda Neslund, Alexandra Jade Garcia  | Socials by: Sofia Del Priore

How do Climate Change and Agriculture Affect Drinking Water?

Throughout the US, agricultural and livestock runoff are some of the largest contributors to drinking water pollution, especially in heavily farmed states like California and Iowa. As part of farming, producers use pesticides and fertilizers which, without strategies like cover cropping, can run off and enter the water stream, leading to elevated levels of dissolved nitrates and phosphorus and causing toxic algal blooms

Climate change associated droughts and floods may be making the problem of agricultural pollutants in water worse by increasing runoff rates, stimulating algal blooms, and reducing the availability of alternative water sources providers can turn to. At the same time, excessive nitrate pollution in agriculture may itself exacerbate greenhouse gas emissions by increasing the nitrous oxide emitted by soil and polluted waters

In Iowa, the Des Moines Department of Water Works is looking for collaborative solutions.

What is Des Moines Water Works Doing About Agricultural Pollution?

Like many water utilities, DMWW is under pressure to remove agricultural pollutants from their water sources, an issue exacerbated by climate change. However, DMWW faces additional challenges as the largest water utility in an agriculturally and livestock intensive state – about 83 percent of Iowa land is farmed, and it’s the top producer of hogs in the US. Widespread use of tile drainage systems, which accelerate the rate that water drains from agricultural land, also increases the amounts of nitrogen and phosphorus that can enter the water stream.

DMWW wants to do more than remove nitrates and phosphates from their water supply via expensive filtration systems – they want to reduce the amounts entering Central Iowa’s water stream to begin with. But because agricultural runoff is considered nonpoint pollution, meaning it can’t be traced back to a single farm, DMWW has no authority with which to force farmers to change their practices and reduce pollution. After attempts at passing stricter pollution regulations were unsuccessful, DMWW filed a lawsuit against 13 Iowa drainage districts over nitrate pollution, but it was dismissed in 2017. Now, they’ve shifted strategies towards educational outreach and collaboration. 

“Protecting source water upstream from us, if we don’t have laws in our favor for that. If we don’t have a lawsuit in our back pocket that we’re going to whip out again, we don’t right now, then we’re left with collaboration,” DMWW External Affairs Manager Jennifer Terry tells Climate Break. “And so I’ve been putting my full weight into collaborating the last year and a half … building coalitions with people that you would maybe consider … unlikely allies.” 

What Does Collaboration Look Like?

As an example, Terry cites the recent purchase of a John Deere cover crop cedar in part partnership with other local organizations. Now, DMWW is working with agricultural retailer Heartland Cooperative to sell its services to central Iowan farmers. Cover cropping can reduce erosion and increase the amount of nutrients retained by soil, preventing pollutants from draining into the water supply. It also has benefits for climate change mitigation: planting cover crops, rather than leaving land bare during the off season, sequesters more carbon in the soil and reduces emissions. 

“Is that project over the next four years going to clean up our rivers? No,” Terry acknowledges, “but what it’s going to do is hopefully demonstrate a scalable model of how municipalities and private industry can come together and hopefully make it win-win-win … [the] land owner gets to keep his or her soil on the farm, we get to keep the contaminants out of the water, and we get to … work together with people who share our values for an end game of cleaner source water.”

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Terry: Nitrogen and phosphorus are generally the contaminants that we struggle with in terms of agricultural production. And those are also the nutrients that feed things like harmful algal blooms. And nutrify the water in the rivers when it comes downstream to us.

Ethan: I’m Ethan Elkind, and you’re listening to Climate Break. You just heard Jennifer Terry, external affairs manager for Des Moines Water Works, Iowa’s largest water treatment utility. She tells us that agricultural pollution in the Des Moines water supply is getting worse with climate change-induced droughts. In the absence of strong federal and state regulations, her utility is collaborating with farmers to help them plant cover crops to reduce polluted runoff.

Terry: There’s. Collaboration there’s litigation there’s regulation, or there’s a combination of all those when you’re trying to reduce nutrient pollution from agriculture. So If we don’t have. Laws in our favor for that. If we don’t have a lawsuit in our back pocket then we’re left with collaboration.

For example, we partnered with a group called the practical farmers of Iowa and put together some money and purchased kind of a revolutionary concept. Purchased a cover crop Cedar, and it’s a John Deere $600,000 cover crop Cedar. and now we are enlisting the help of an agricultural retailer Heartland cooperative to go out and of sell these services to farmers and one of our little source watersheds.

If you use cover crops, it’s going to build the organic matter in your soil, and it’s going to keep the soil in place and keep those pollutants from leaving your property.

And so is that project over the next four years going to clean up our rivers? No, but what it’s going to do is demonstrate a scalable model of how municipalities and private industry can come together and hopefully make it win-win-win.

Ethan: To learn more about Des Moines Water Works and how to protect your local watershed from pollution and climate change impacts, visit

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