Warming winters lead to more nitrate pollution in the drinking water near farms

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.