Preprints
https://doi.org/10.5194/hess-2020-423
https://doi.org/10.5194/hess-2020-423

  14 Sep 2020

14 Sep 2020

Review status: this preprint has been withdrawn by the authors.

Seasonal watershed-scale influences on nitrogen concentrations across the Upper Mississippi River Basin

Michael L. Wine1,2, Heather E. Golden3, Jay R. Christensen3, Charles R. Lane3, and Oleg Makhnin4 Michael L. Wine et al.
  • 1Oak Ridge Institute for Science and Education at U.S. Environmental Protection Agency, Office of Research and Development, Cincinnati, 45268, United States
  • 2Currently Independent Scientist, Denver, 80222, USA
  • 3U.S. Environmental Protection Agency, Office of Research and Development, Cincinnati, 45268, United States
  • 4Department of Mathematics, New Mexico Institute of Mining and Technology, Socorro, 87801, United States

Abstract. Humanity's footprint on Earth systems has engendered water quality impoverishment in streams, lakes, and coastal waters globally. In agricultural areas, stream nitrogen concentrations are often high where excess nitrogen fertilization and wetland loss via artificial drainage degrade water quality. While the watershed-scale influence of fertilization and wetland loss on annual nitrogen loads has been studied, little is known about the watershed-scale effects of these wetland losses at seasonal time scales. Here we apply machine learning and linear statistical analyses in a big data framework to improve understanding of the role wetlands play in influencing the seasonality of down-gradient water quality. We confirm the seasonal role of wetlands in improving water quality at the watershed scale and uncover evidence demonstrating the importance of contemporary watershed nitrogen inputs to in-stream total nitrogen concentrations [TN]. We observe that in the Upper Mississippi River Basin, United States, after the application of spring fertilizers, [TN] drops by 70 % from June to September suggesting the importance of seasonal nutrient loading. Our data mining approach affords exploration of the potential influence of numerous landscape and wetland hydrologic processes on [TN], some of which are shown to exert seasonal influence. Our counterfactual analysis–in which wetlands are restored to their historic extent–points to the substantial water quality benefits of wetland restoration, including particular water quality improvements in the spring when [TN] are highest. Water quality benefits due to wetland restoration would make water safer for human consumption and improve the security of aquatic ecosystems.

This preprint has been withdrawn.

Michael L. Wine et al.

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Interactive discussion

Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Michael L. Wine et al.

Michael L. Wine et al.

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This preprint has been withdrawn.

Short summary
Mirroring a global water quality crisis, nitrogen concentrations in the Upper Mississippi River basin, USA regularly exceed levels considered safe for human consumption and aquatic exposure, particularly following fertilization in the spring. Counterfactual simulations suggest that restoring the historic distribution of wetlands would substantially reduce nitrogen concentrations, particularly when they are most elevated, in the spring. Results point to a tradeoff between food and water security.