Articles | Volume 25, issue 2
Hydrol. Earth Syst. Sci., 25, 811–829, 2021
Hydrol. Earth Syst. Sci., 25, 811–829, 2021

Research article 19 Feb 2021

Research article | 19 Feb 2021

Determination of vadose zone and saturated zone nitrate lag times using long-term groundwater monitoring data and statistical machine learning

Martin J. Wells et al.

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Revised manuscript under review for HESS
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Cited articles

Anning, D. W., Paul, A. P., McKinney, T. S., Huntington, J. M., Bexfield, L. M., and Thiros, S. A.: Predicted Nitrate and Arsenic Concentrations in Basin-Fill Aquifers of the Southwestern United States, United States Geological Survey Scientific Investigations Report 2012–5065, 78, available at: (last access: 8 February 2021), 2012. 
Babcock, H. M., Visher, F. N., and Durum, W. H.: Ground-Water Conditions in the Dutch Flats Area, Scotts Bluff and Sioux Counties, Nebraska, United States Geological Survey Circular 126, 51, available at: (last access: 8 February 2021), 1951. 
Böhlke, J. K.: Groundwater Recharge and Agricultural Contamination, Hydrogeol. J., 10, 153–179,, 2002. 
Böhlke, J. K. and Denver, J. M.: Combined Use of Groundwater Dating, Chemical, and Isotopic Analyses to Resolve the History and Fate of Nitrate Contamination in Two Agricultural Watersheds, Atlantic Coastal Plain, Maryland, Water Resour. Res., 31, 2319–2339,, 1995. 
Short summary
Groundwater in many agricultural areas contains high levels of nitrate, which is a concern for drinking water supplies. The rate at which nitrate moves through the subsurface is a critical piece of information for predicting how quickly groundwater nitrate levels may improve after agricultural producers change their approach to managing crop water and fertilizers. In this study, we explored a new statistical modeling approach to determine rates at which nitrate moves into and through an aquifer.