This map shows the approximate locations of community water systems in Minnesota with nitrate contamination of drinking water that got worse between 1995 and 2018. A community system is what most people think of as a water utility, mainly serving places where people live, such as cities and towns.
Clicking on a point brings up the name of the community water system, whether the system gets its drinking water from a groundwater or surface water source, and the population served by the system. Each system also has a chart that shows the highest nitrate test per year found by the system, the average nitrate concentration per year and a reference line at the 3 mg/L level.
The Minnesota Department of Health says a level of 3 mg/L indicates that “human-made sources of nitrate have contaminated the water and the level could increase over time.” The map includes only systems with at least one test at or above that level.
The final component of each pop-up box is a table with the total number of nitrate tests conducted by the system between 1995 and 2018, and the number at or above 3, 5 and 10 mg/L.
The data come from Freedom of Information Act requests fulfilled by the Minnesota Department of Health. Some of the data can also be found on the U.S. Environmental Protection Agency’s Safe Drinking Water Information System website.
To see the methods and detailed results of this study, click here.