Who is most likely to drink high-nitrate ground water?
Where people live and the depth of their ground-water supply determine the quality of the water they drink. In figure 3, four ranges of depth to ground water are shown for the high-risk (red) areas on the national map. Nitrate contamination generally decreases with increasing depth to ground water. Median nitrate concentration and percent of wells from which water exceeds the EPA drinking-water standard for nitrate (10 mg/L) are highest for shallow ground water (up to 100 feet deep). The water table in shallow wells is closer to the land surface and to potential sources of contamination, such as fertilizers and septic systems. In contrast, contamination is less likely to occur in deeper ground-water reservoirs because contaminants have farther to travel (Mueller and others, 1995).
