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About the Map

Iowa’s Private Wells Contaminated by Nitrate and Bacteria

Click on a county to see county-level information about:

• The number of wells tested for nitrate or bacteria between 2002 and 2017.
• How many wells had average nitrate at or above 5 mg/L, excluding 2014.
• The number of wells with at least one positive coliform or fecal coliform bacteria test.
• How many wells had both elevated nitrate concentrations and the presence of bacteria.

Click each of the three different map layers to turn them on or off.

• The “nitrate” layer shows Iowa private wells that had average nitrate concentrations at or above 5 mg/L between 2002 and 2017, excluding 2014, but not any positive tests for bacteria.
• The “bacteria” layer has private wells that had one or more tests positive for bacteria between 2002 and 2017 but had average nitrate concentrations below 5 mg/L.
• The “bacteria nitrate” layer displays the private wells that had both their average nitrate concentrations at or above 5 mg/L and at least one positive test for bacteria.

The individual well points are not interactive.

The eight counties shaded darker gray tested at most 10 wells for nitrate or bacteria between 2002 and 2017. This incredibly low amount of testing does not allow anyone to grasp the true scope of the contamination problems in these counties. All other counties are shaded lighter gray, and tested more than 10 wells.

To find out more about the map, click here.

Data for this map was gathered using the Iowa Department of Natural Resources’ Private Well Tracking System.

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