More than half of Iowa waterways had nitrate contamination above federal drinking water standard last week, the Iowa Water Quality Information System showed.

Some were at levels typically not seen until later in the year.

University of Iowa scientists reported that weeks of warm spring temperatures and steady rain led to a spike in nitrate, which can rob oxygen from babies' blood. Nitrate, which occurs naturally and also comes from farm fertilizers, is at the heart of a federal lawsuit in which Des Moines Water Works contends the drainage ditches run by three northwest Iowa counties should be regulated under the U.S. Clean  Water Act.

The widespread nitrate pollution last week also came soon after many farmers applied anhydrous ammonia to fields, UI reported.
 
Nitrate levels are well ahead of where they were in previous years by this time, UI reported. The North Raccoon River levels were running as high as they were in late May last year and September of 2014. The South Fork Iowa River in north-central Iowa was running about double the drinking water limit.

More information is available from Iowa Water Quality Information System.