Recent rainfall in Iowa has led to an increase in nitrate levels in the state’s water supply, according to Matt Helmers, director of the Iowa Nutrient Research Center at Iowa State University. Helmers explained that rain washes out nitrates from fertilizer and manure applied on fields, which then flow into streams and rivers.

Nitrate Levels and Weather Patterns

The ebb and flow of rain affects nitrate levels, as seen in the number of days the Central Iowa Water Works runs its nitrate removal facility. In 2015, the facility operated for 177 days, following a drought. The number of days it has run from 2013 to 2025 varies, with 163 days in 2026 so far.

Nitrates are a regulated contaminant, with the Environmental Protection Agency setting a standard of 10 milligrams per liter for drinking water. High nitrate levels in 2025 and 2026 resulted in lawn watering bans. Helmers and his colleagues are studying these trends to better understand the lag times after weather events.

Original reporting: KCCI Des Moines — read the source article.