Ag fertilizer runoff likely will force more drinking water restrictions

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The Raccoon River weaves past downtown Des Moines, Iowa, in June. One of the primary drinking water sources for the region, the river has high nitrate levels that have led to water restrictions for some 600,000 customers. (Cami Koons/Iowa Capital Dispatch)

For nearly a month, hundreds of thousands of Iowans have not been allowed to water their lawns — even though there’s no drought.

Local authorities previously asked the public to refrain from washing cars and filling pools. And some cities turned off splash pads in the height of summer heat.

While such measures are common during dry periods, there’s no shortage of water: Rather, the water in and around Des Moines contains too much nitrate, a natural component of soil and a byproduct of commercial fertilizer and livestock manure. Persistent rainfall has flushed nutrients out of fertilized fields into streams and rivers.

While the water bans are temporary, they’re the starkest sign yet of the state’s long-brewing struggle with high nitrate levels in streams and rivers that supply drinking water.

“It’s a big deal: the first time ever that lawn watering has been banned,” said Tami Madsen, executive director of Central Iowa Water Works, a regional water authority serving 600,000 people.

Federal law limits nitrate levels in drinking water because of its association with infant asphyxia, also known as blue baby syndrome. And a growing body of research has found links between nitrate consumption and cancer.

While Iowa’s problems are uniquely severe, nitrate levels are a rising concern in other regions, from California to the Chesapeake Bay. And climate change is expected to worsen the problem as more intense cycles of drought and severe storms increase farm runoff.

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Iowa’s concentration of fertilized row crops and massive livestock confinements that produce tons of nitrogen-rich manure have caused concerns over increased nitrate levels for years. And the state’s unique underground system of farm drainage pipes quickly pumps nitrate and other nutrients into streams and rivers.

The water system serving the Des Moines metro area has invested heavily in nitrate filtration and removal equipment. The primary facility in Des Moines, one of the largest nitrate removal systems in the world, costs $16,000 per day to operate, Madsen said.

“I’m confident in our ability to continue to provide safe drinking water,” Madsen said. “It’s just going to be at what cost.”

More frequent and extreme storms because of climate change will heighten the problems nationwide, said Rebecca Logsdon Muenich, an associate professor of biological and agricultural engineering at the University of Arkansas.

Because nitrogen travels with water, nitrate levels are especially hard to control during times of severe weather.

Muenich said farm conservation practices such as establishing wetlands and landscape buffers can help keep nitrogen out of water supplies. But the growth of the livestock industry, availability of cheap crop fertilizer and lack of regulation over nitrogen application make nitrate levels hard to control.

“We’ve kind of put ourselves in a bind unless we start investing in better technologies or more conservation,” she said.

The role of agriculture

As hundreds of thousands of residents were being asked to conserve water last month, a group of 16 experts released a years-in-the-making report analyzing the quality of the Raccoon and Des Moines rivers, the main sources of drinking water for the Des Moines region.

The researchers found that central Iowa rivers have some of the nation’s highest nitrate levels, routinely exceeding the federal drinking water standard. While some pollutants are naturally occurring, the researchers concluded that most of the nitrogen in the two rivers comes from farmland.

Commissioned in 2023 by Polk County, the state’s most populous county and home to Des Moines, the report underscored the connection between industrial agriculture and water quality.

Larry Weber, a professor of civil and environmental engineering at the University of Iowa who worked on the report, said Iowa’s problem spreads to other areas: Iowa waterways export hundreds of millions of pounds of nitrogen per year, much of it flowing into the Mississippi River and eventually the Gulf of Mexico’s dead zone.

He said water restrictions may become more common as more cities confront high nitrate levels.

“This is happening more frequently and it’s going to continue to happen more frequently,” he said.

Weber said individual farmers aren’t necessarily to blame for the crisis. They’re doing their best to survive market demands and operate within federal farm policy. But he said the broader industry and the state could do more to invest in conservation methods to prevent pollution.

He noted that Iowa lawmakers in 2023 cut $500,000 for a water quality monitoring network across the state. While the Iowa Nutrient Research Center received a short-term grant to stay open, Weber said next year it will shut down 75 sensors that measure nitrate and other pollutants in state waters.

“The agricultural system doesn’t want this unfortunately difficult information to be made available,” he said.

A spokesperson for the Iowa Farm Bureau referred questions to the state agriculture department.

In a statement to Stateline, Agriculture Secretary Mike Naig, a Republican, said many Iowa groups are working on conservation and infrastructure projects to improve water quality.

“We’re not interested in stoking animosity between rural and urban neighbors,” the statement said. “Agriculture, conservation, recreation, urban and rural development, and business growth can and must co-exist in Iowa.”

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In a lengthy social media post last month, Naig said nitrate levels were primarily driven by weather and stream flows. The secretary said advances in farming practices can help farmers apply fertilizer more efficiently and touted efforts such as new wetlands and structures that reduce stream erosion. But he said the fast-growing Des Moines area also needed to examine its investments in water treatment infrastructure to meet future needs.

“The blame game is unproductive,” he wrote.

On Tuesday, Naig’s department announced a $1.9 million water quality project upstream of Des Moines. That project will install landscape buffers and bioreactors to help reduce runoff of nitrate and other nutrients. The department is contributing $244,000 of that money.

Matt McCoy, chair of the Polk County Board of Supervisors, said that local government is trying to work with landowners and farmers to prevent water pollution. The county has spent millions on projects to seed cover crops and plant vegetative buffers between fields and waterways to prevent runoff of pollutants, including nitrogen.

“I don’t think we want to disparage agriculture and farming because it’s such a big part of who we are as a state,” McCoy said.

A former Democratic state lawmaker, McCoy said the recent water restrictions and daily news reports on nitrate levels in local rivers have elevated public awareness of water quality concerns.

“There are conversations that I know are happening now that were not happening prior to the restrictions,” he said.

Citizen action

The water restrictions in Iowa sparked an influx of interest from locals in the Izaak Walton League of America’s Nitrate Watch program, which provides volunteers with nitrate test kits and maps the results from across the country.

Heather Wilson, the league’s Midwest Save Our Streams coordinator, said the nonprofit environmental organization received more than 300 inquiries from Iowans during a single week in June. For comparison, the organization received about 500 inquiries from across the nation during the first six months of the year.

While the problems in the Des Moines area are severe, she said, volunteers are recording rising nitrate levels across the state. The project gives people who can often feel helpless an active way to contribute to the understanding of nitrate pollution.

“It’s really empowering to be able to put resources in people’s hands so that they can measure the waterways that they personally care about,” she said.

Retired science teacher Birgitta Meade has been testing nitrates around her rural northeast Iowa home for years both as classroom instruction and for Nitrate Watch.

“They’re higher than I have ever tested at any prior point,” she said. “I feel like I’m meticulously documenting the death of my home and nobody else gives a rip.”

Meade said she’s considering investing in a reverse osmosis system to remove nitrates from her home’s private well. Though her nitrate levels are below the federal drinking water standard, she pointed to the growing body of research linking cancer with consumption of nitrate — even at lower levels.

Meade acknowledged the pressures facing farmers, but she said she grows frustrated every time she drives past giant storage containers full of fertilizer and other farm chemicals.

“These are people who are choosing to poison their neighbors,” she said. “And this is just untenable.”

Small towns struggle

Climate change will only intensify nitrogen pollution, said Thomas Harter, a professor and water researcher at the University of California, Davis. Last year, he worked on research that found drought and heavy rains accelerate the speed of nitrogen absorption into groundwater.

In some parts of California’s Central Valley, nearly a third of drinking and irrigation wells exceed federal nitrogen standards.

“We are ever more productive on the grower side, and that means more fertilizer being used and more fertilizer being lost to groundwater and to streams,” Harter said.

That’s particularly challenging for drinking water systems serving small population bases.

“It gets really expensive for really small systems and it’s also a lot of maintenance,” he said.

That’s a reality currently facing Pratt, Kansas, a community of about 6,500 people, where some wells have recorded nitrate levels above the federal standard.

City Manager Regina Goff said nitrate levels are pushing the community’s pursuit of a new water treatment facility that’s expected to cost upward of $45 million. The city’s proposed 2025 budget totaled about $35.7 million.

Goff said the city is exploring financing options, including potential grants. But she said it’s frustrating for the town to spend so much to meet regulatory standards for safe drinking water, which she characterized as an “unfunded mandate.”

Currently, nearly a quarter of the city’s groundwater supply is unavailable because of high nitrate levels. But the city must notify residents of high nitrate levels even in wells that are not pumping.

“It causes a panic,” Goff said. “That’s been a hard pill for us to swallow as a city — that we have to alarm our population even though we know there’s no possibility of harm.”

Stateline is part of States Newsroom, a nonprofit news network supported by grants and a coalition of donors as a 501c(3) public charity. Stateline maintains editorial independence. Contact Editor Scott S. Greenberger for questions: [email protected].

This post was originally authored and published by Kevin Hardy from Missouri Independent via RSS Feed. Join today to get your news feed on Nationwide Report®.