Data from the Iowa Water Quality Information System showed that more than half of Iowa’s monitored waterways exceeded the nitrate threshold for drinking water after a week of heavy rains in early May.
Weeks of warm spring temperatures followed by consistent rain throughout the state may have contributed to a spike in nitrate in Iowa’s waterways. The nitrate was washed out of fields where it had previously been applied in fertilizers, either as part of the planting process or in the form of anhydrous ammonia in the fall.
Nitrate is a pollutant that must be removed at water treatment plants before water can be suitable for drinking, sometimes at great cost to the plants. The Des Moines Water Works is suing three northwest Iowa counties for failing to control the pollution of Raccoon River drinking water that water works customers must then pay to treat.
For more information about the Iowa Water Quality Information System and a useful tutorial on the program, visit the Iowa Environmental Focus website.