Is the River a Chemostat? Scale Versus Land Use Controls on Nitrate Concentration-Discharge Dynamics in the Upper Mississippi River Basin

Richard E. Marinos, Kimberly J. Van Meter, Nandita B. Basu

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The Upper Mississippi River Basin is the largest source of reactive nitrogen (N) to the Gulf of Mexico. Concentration-discharge (C-Q) relationships offer a means to understand both the terrestrial sources that generate this reactive N and the in-stream processes that transform it. Progress has been made on identifying land use controls on C-Q dynamics. However, the impact of basin size and river network structure on C-Q relationships is not well characterized. Here, we show, using high-resolution nitrate concentration data, that tile drainage is a dominant control on C-Q dynamics, with increasing drainage density contributing to more chemostatic C-Q behavior. We further find that concentration variability increases, relative to discharge variability, with increasing basin size across six orders of magnitude, and this pattern is attributed to different spatial correlation structures for C and Q. Our results show how land use and river network structure jointly control riverine N export.

Original languageEnglish (US)
Article numbere2020GL087051
JournalGeophysical Research Letters
Issue number16
StatePublished - Aug 28 2020

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Earth and Planetary Sciences(all)

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