http://droughtreporter.unl.edu/

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Nitrogen fertilizer can accumulate in farm fields during years of drought and can wash into streams in large amounts when rain returns and brings an end to drought. Such an event is occurring in Iowa’s large rivers, including the Boone, Cedar, Iowa and Turkey rivers, where concentrations have hit four-year highs. Stream flows are much higher than usual, and concentrations are extremely high, so the total nitrate load is also very high. “This is one of the biggest nitrate leaching events in 11 years,” according to David Cwiertny, director of the Center for Health Effects of Environmental Contamination at the University of Iowa. Water quality experts anticipated such a spike in pollution after significant rain fell after years of drought. More than twice the normal rain has fallen in recent weeks in Iowa, providing this wave of moisture to wash the nitrate out of the soil and into streams and rivers. Des Moines Water Works started its nitrate removal system on May 13 as the nitrate concentration in the Raccoon River, one of the main water sources, exceeded 15 parts per million. In March, the concentration was about 1 part per million, per DMWW data. Nitrate levels were extraordinarily high in other rivers, according to the Iowa Water Quality Information System. The Turkey River near Garber had a nitrate level of 18 parts per million. The Cedar River near Janesville reached 24 parts per million. And the Boone River near Webster City hit 25 parts per million. Iowa Capital Dispatch (Des Moines), May 12, 2024