When pollution levels rise in the rivers that supply drinking water to Iowa’s largest city, Des Moines must spend roughly $16,000 each day to operate a specialized system that removes hazardous nitrates. This recurring expense has become part of life in an agriculture-driven state — and climate change is intensifying the challenge. Nitrates originate from fertilizers and pesticides that seep into the soil and eventually flow into waterways such as the Raccoon and Des Moines rivers. Typically,