, Volume 18, Issue 8, pp 1319–1331 | Cite as

Climate Variation Overwhelms Efforts to Reduce Nitrogen Delivery to Coastal Waters

  • Neil D. Bettez
  • Jonathan M. Duncan
  • Peter M. Groffman
  • Lawrence E. Band
  • Jarlath O’Neil-Dunne
  • Sujay S. Kaushal
  • Kenneth T. Belt
  • Neely Law


We calculated watershed nitrogen (N) retention (inputs–outputs)/inputs) each year from 1999–2013 for nine sub-watersheds along an urban–rural gradient near Baltimore MD to determine how land use and climate influence watershed N flux. Retention is critical to efforts to control coastal eutrophication through regulatory efforts that mandate reductions in the total maximum daily load (TMDL) of N that specific water bodies can receive. Retention decreased with urbanization as well as with increases in precipitation with retention decreasing from an average of 91% in the forested sub-watershed to 16% in the most urban sub-watershed. Export was 23% higher, and retention was 7% lower in winter (November–April) than during the growing season. Total N delivery to Baltimore Harbor varied almost threefold between wet and dry years, which is significant relative to the total annual export allowed for all non-point sources to the harbor under the TMDL. These results suggest that expectations for TMDLs should consider watershed land use and climate variability, and their potential for change if they are to result in improvements in receiving water quality.


Nitrogen cycling Urban systems Watershed Total maximum daily load 



The data for this paper are available at the Baltimore Ecosystem Web site ( This work was funded by the U.S. National Science Foundation: NSF-EAR award #0847838 to N.D.B and NSF-DEB award #1027188 (Baltimore LTER). Special thanks to Dan Dillon, who provided valuable assistance and advice in the field, Lisa Martel, Robin Schmidt, Kate Shepard, and Amanda Irish who processed and analyzed samples in the laboratory and two anonymous reviewers who provided two rounds of valuable and constructive comments and suggestions.

Supplementary material

10021_2015_9902_MOESM1_ESM.pdf (53 kb)
Monthly Precipitation, Temperature, TN Flux, and Discharge for the Gwynns Falls. Supplementary material 1 (PDF 52 kb)


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Copyright information

© Springer Science+Business Media New York 2015

Authors and Affiliations

  • Neil D. Bettez
    • 1
  • Jonathan M. Duncan
    • 2
  • Peter M. Groffman
    • 1
  • Lawrence E. Band
    • 2
  • Jarlath O’Neil-Dunne
    • 3
  • Sujay S. Kaushal
    • 4
  • Kenneth T. Belt
    • 5
  • Neely Law
    • 6
  1. 1.Cary Institute of Ecosystem StudiesMillbrookUSA
  2. 2.Department of Geography and Institute for the EnvironmentUniversity of North CarolinaChapel HillUSA
  3. 3.Rubenstein School of Environment and Natural Resources and Spatial Analysis LabUniversity of VermontBurlingtonUSA
  4. 4.Department of Geology and Earth System Science Interdisciplinary CenterUniversity of MarylandCollege ParkUSA
  5. 5.USDA Forest ServiceBaltimore Field StationBaltimoreUSA
  6. 6.Center for Watershed ProtectionEllicott CityUSA

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