Trends in Drinking Water Nitrate (On Demand Available)

Excess nitrate in drinking water is a human health concern, especially for young children. This presentation highlights the results of several research projects related to explaining the temporal and spatial trends in drinking water nitrate across the  United States.

The results of these studies show that most "maximum contaminant level (MCL) violations are in small, non-community, groundwater systems, and some groundwater systems have persistent nitrate contamination, but one large surface water system in violation can potentially impact millions of people.  The results also show the locations and factors (e.g., nitrogen inputs, precipitation) that are associated with higher risks for drinking water nitrate violations.  Changes in both nitrogen inputs and public water system operation both play a role in shaping the trends in drinking water nitrate.  On average, wildfires are associated with increased surface water nitrate violations and the elevated nitrate can last multiple years post wildfire. This work could help inform management decisions aimed at minimizing public health risks associated with drinking water nitrate.

The results from the first study assessed temporal and geographic trends for violations of the MCL in the conterminous U.S.  The second study shows results of models used to determine the drivers of nitrate violations and predict where public water systems are at risk of exceeding MCLs. The third study attempts to determine the main causes for temporal declines in drinking water nitrate violations, such as due to reductions in nitrogen inputs, improved drinking water system treatment or better source water protection measures. The fourth study examines post-wildfire effects on nitrate violations and concentrations, and a planned fifth study will examine whether future changes in temperature, precipitation, land use, and nitrogen inputs may alter where drinking water systems are most at risk for violations of the MCL.

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