, Volume 79, Issue 1–2, pp 163–186 | Cite as

The influence of climate on average nitrogen export from large watersheds in the Northeastern United States

  • R.W. Howarth
  • D.P. Swaney
  • E.W. Boyer
  • R. Marino
  • N. Jaworski
  • C. Goodale


The flux of nitrogen in large rivers in North America and Europe is well explained as a function of the net anthropogenic inputs of nitrogen to the landscape, with on average 20 to 25% of these inputs exported in rivers and 75 to 80% of the nitrogen retained or denitrified in the landscape. Here, we use data for average riverine nitrogen fluxes and anthropogenic inputs of nitrogen over a 6-year period (1988–1993) for 16 major watersheds in the northeastern United States to examine if there is also a climatic influence on nitrogen fluxes in rivers. Previous studies have shown that for any given river, nitrogen fluxes are greater in years with higher discharge, but this can be interpreted as storage of nitrogen in the landscape during dry years and flushing of this stored nitrogen during wet years. Our analyses demonstrate that there is also a longer-term steady-state influence of climate on riverine nitrogen fluxes. Those watersheds that have higher precipitation and higher discharge export a greater fraction of the net anthropogenic inputs of nitrogen. This fractional export ranges from 10 to 15% of the nitrogen inputs in drier watersheds in the northeastern United States to over 35% in the wetter watersheds. We believe this is driven by lower rates of denitrification in the wetter watersheds, perhaps because shorter water residence times do not allow for as much denitrification in riparian wetlands and low-order streams. Using mean projections for the consequences of future climate change on precipitation and discharge, we estimate that nitrogen fluxes in the Susquehanna River to Chesapeake Bay may increase by 3 to 17% by 2030 and by 16 to 65% by 2095 due to greater fractional delivery of net anthropogenic nitrogen inputs as precipitation and discharge increase. Although these projections are highly uncertain, they suggest a need to better consider the influence of climate on riverine nitrogen fluxes as part of management efforts to control coastal nitrogen pollution.


Nitrogen Nutrients Nitrogen flux Nitrogen pollution Denitrification Climate change Net anthropogenic nitrogen inputs NANI Watersheds River River basin 


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We thank Steven Ellner and Åsa Danielsson for helpful discussions of the statistical aspects of our analyses and Alan Townsend, Greg McIsaac, Sybil Seitzinger, and Ken Staver for comments on earlier drafts of the manuscript. This research was funded by grant R830882 from the EPA STAR program, by a USDA Hatch grant, and by an endowment provided to Cornell University by␣David R. Atkinson.


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Copyright information

© Springer Science+Business Media, Inc. 2006

Authors and Affiliations

  • R.W. Howarth
    • 1
  • D.P. Swaney
    • 1
  • E.W. Boyer
    • 2
  • R. Marino
    • 1
  • N. Jaworski
    • 3
  • C. Goodale
    • 1
  1. 1.Department of Ecology & Evolutionary BiologyCornell UniversityIthacaUSA
  2. 2.Department of Environmental Science, Policy & ManagementUniversity of CaliforniaBerkeleyUSA
  3. 3.U.S. Environmental Protection Agency (retired)NarragansettUSA

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