"When pollution gets bad enough in the rivers supplying Iowa’s largest city with drinking water, it costs Des Moines around $16,000 a day to run a special system to filter out dangerous nitrates. It’s a fact of life in the agriculture-dependent state — and climate change is making the water quality problem even worse.
The nitrates come from fertilizer and pesticides that make their way into the soil and then waterways like the Raccoon and Des Moines rivers. It’s not usually a problem in winter, but this year Iowa’s capital had to filter in January and February — just the second time that’s happened in more than 30 years. That’s likely going to mean higher water bills for people who live in a state with some of the nation’s waterways that are most vulnerable to nitrate pollution.
Experts blame weather conditions, including warming winters, for a costly problem they say will only grow across farm country.
When it comes to winter nitrate pollution events, “We are more apt to see these in the future. Are they going to occur every year? No. But the ingredients are there for them to potentially occur more often,” said Justin Glisan, Iowa’s state climatologist."
Melina Walling reports for the Associated Press April 1, 2026.
