Groundwater quality in principal aquifers of the lower 48 United States

The proportion of each aquifer with contaminant levels that exceed human-health guidelines. Groundwater quality relative to the human-health benchmark for drinking water. For each principal aquifer in the lower 48 United States, a pie chart shows the proportion of the aquifer with contaminant levels for selected contaminants (including arsenic, manganese, lead, and nitrate).

Image from: https://water.usgs.gov/vizlab/water-availability/