Warming Winters Exacerbate Nitrate Pollution in Iowa Drinking Water

Climate change is making it harder for Iowa's capital city to keep nitrate levels out of its drinking water supply.

Apr. 1, 2026 at 1:12pm

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Abnormally high nitrate pollution levels in Iowa's waterways this past winter have forced the state's largest city, Des Moines, to run an expensive nitrate removal system that is usually only needed during the summer months. Experts say warming winters are causing more fertilizer and pesticide runoff to make its way into rivers and streams, leading to increased nitrate contamination of drinking water supplies. This issue disproportionately impacts low-income and rural communities that lack the infrastructure to properly filter out nitrates.

Why it matters

Nitrate pollution in drinking water is a growing problem across the U.S., especially in agricultural regions like Iowa. As climate change leads to warmer and wetter winters, the increased runoff of farm chemicals is straining the ability of water treatment facilities to keep up. This is resulting in higher costs for consumers and raising concerns about the long-term health impacts, particularly for vulnerable populations.

The details

The nitrates come from fertilizers and pesticides used on farms that then make their way into waterways like the Raccoon and Des Moines rivers. While this is usually not an issue in the winter, this year Iowa's capital had to filter the water in January and February - only the second time that has happened in over 30 years. Filtering out the dangerous nitrates costs Des Moines around $16,000 per day, a cost that will likely be passed on to residents through higher water bills.

  • In January and February 2026, Des Moines had to filter its drinking water to remove abnormally high nitrate levels.
  • This is only the second time in over 30 years that Des Moines has had to filter its water during the winter months.

The players

Delaney Bullock

A graduate student at the University of Vermont who gathers runoff samples from agricultural fields to be analyzed for nutrient concentrations.

Samuel Sandoval Solis

A professor at the University of California-Davis and an extension specialist in water resources management.

Joan Cox

The program manager for the Illinois Nutrient Loss Reduction Strategy.

Carol Adair

A professor at the University of Vermont who has studied how rain-on-snow events could worsen nutrient pollution.

Dani Replogle

A staff attorney for the nonprofit Food and Water Watch, which advocates for sustainable food and clean water.

Amy Kahler

The CEO and general manager at Des Moines Water Works.

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What they’re saying

“Nitrate pollution is a big problem for low-income, rural residents across the United States.”

— Samuel Sandoval Solis, Professor, University of California-Davis

“There really are two paths. One is conservation efforts and responsible watershed practices. And the other is spending hundreds of millions of dollars in treatment solutions.”

— Amy Kahler, CEO and General Manager, Des Moines Water Works

“Everything is becoming so unpredictable.”

— Dani Replogle, Staff Attorney, Food and Water Watch

What’s next

Des Moines Water Works is preparing resiliency plans to address the growing issue of increased winter nutrient pollution, but experts say the best solution is for upstream polluters to implement more conservation efforts and responsible watershed practices.

The takeaway

This story highlights how climate change is exacerbating the longstanding problem of nitrate pollution in drinking water, disproportionately impacting low-income and rural communities that lack the resources to properly filter their water. It underscores the need for proactive measures to address agricultural runoff and invest in water infrastructure resilience.