Protecting Drinking Water from Agricultural Pollutants with Des Moines Water Works

Image Credits: Wheat is planted as a cover crop on cotton fields using a cover crop seeder. Cover crops are one of the agricultural techniques Des Moines Water Works hopes can reduce the polluted runoff entering Iowa’s largest rivers. Image by: Katie Nichols

Audio Editing by: Xu Wangyuxan Blurb by: Marie Hogan Script by: Marie Hogan

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 non-point source 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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Ethan: I’m Ethan Elkind, and you’re listening to Climate Break — climate solutions in a hurry. Today’s proposal: How water treatment utilities can help farmers reduce pollution in our waterways in the face of worsening climate change-induced droughts. Here’s Jennifer Terry, external affairs manager for water treatment utility Des Moines Water Works in Iowa.

Jennifer Terry: So the water, when it snakes its way down to us, runs through heavily farmed and tilled land. And so when we don’t use things like cover crops that keep the land coverage during the winter months, the land is bare a lot of the year on corn and soybean fields.

Ethan: This bare land means more nutrient-rich farm runoff enters local waterways. As climate change contributes to more severe droughts, Terry says the nutrients get so concentrated that they cause harmful algal blooms that threaten drinking water supplies.

Jennifer Terry: We are just weathering a really severe drought. So one of our rivers was so low that you could walk across it last year.

Ethan: Weak standards on agricultural runoff means Des Moines Water Works has had to get creative. So they’re helping local farmers reduce this bare land by planting cover crops.

Jennifer Terry: For example, we partnered with a group called the practical farmers of Iowa and put together some money and purchased a John Deere $600,000 cover crop seeder. And now we are enlisting the help of an agricultural retailer, Heartland cooperative, to sell these services to farmers in one of our little source watersheds.

Jennifer Terry: 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

Protecting Drinking Water from Agricultural Pollutants with Des Moines Water Works