More than 90 percent of the nitrogen transported by Iowa streams is in the form of nitrate (NO3-N).

When Iowans straightened rivers and creeks in the 20th century, they likely didn’t understand the chain reaction they had set in motion. They simply wanted to make their land easier to farm. But according to IIHR Research Engineer Chris Jones, the straightened dredge ditches of today are disconnected from the floodplain and have lost much of their ability to process nutrients. The water moves faster, eroding downward and increasing the flood risk downstream.

Determining trends is tricky business. You’re looking into the past at water quality data to see if you can discern what has happened. Then you try to see if these changes correlate with something else: local, state, and federal policy; land use changes; advances in technology. The problem we have with this approach here in Iowa is that year-to-year weather variations are large, some would say extreme.

First Quarter nitrate levels in the Raccoon and Des Moines Rivers (at Des Moines) were above average in 2017 compared to the historical record.