Low levels of nitrate-N (below 1 mg/L) can occur naturally in groundwater. However, elevated levels of nitrate-N are indicative of impacts from human land use. The WGCC (Wisconsin Groundwater Coordinating Council) report states approximately 90% of all nitrate-N inputs to groundwater originate from agricultural sources, 9% from septic systems, and 1% from lawns or other sources. While nitrate-N contamination of drinking water can be found throughout the state, there are certain areas that are more susceptible due to naturally occurring geology and human land uses.
To learn more about the Nitrate-N in drinking water, visit the Wisconsin Department of Health Services Website.