Upstream-to-downstream changes in nutrient export risk

  • Authors: Wickham, James D.; Wade, Timothy G.; Riitters, Kurt H.; O’Neill, R.V.; Smith, Jonathan H.; Smith, Elizabeth R.; Jones, K.B.; Neale, A.C.
  • Publication Year: 2003
  • Publication Series: Miscellaneous Publication
  • Source: Landscape Ecology 18:195-208

Abstract

Abstract: Nutrient export coefficients are estimates of the mass of nitrogen (N) or phosphorus (P) normalized by area and time (e.g., kg/ha/yr). They have been estimated most often for watersheds ranging in size from 102 to 104 hect-ares, and have been recommended as measurements to inform management decisions. At this scale, watersheds are often nested upstream and downstream components of larger drainage basins, suggesting nutrient export co-efficients will change from one subwatershed to the next. Nutrient export can be modeled as risk where lack of monitoring data prevents empirical estimation. We modeled N and P export risk for subwatersheds of larger drainage basins, and examined spatial changes in risk from upstream to downstream watersheds. Spatial (sub-watershed) changes in N and P risk were a function of in-stream decay, subwatershed land-cover composition, and subwatershed streamlength. Risk tended to increase in a downstream direction under low rates of in-stream decay, whereas high rates of in-stream decay often reduced risk to zero (0) toward downstream subwatersheds. On average, increases in the modeled rate of in-stream decay reduced risk by 0.44 for N and 0.39 for P. Interactions between in-stream decay, land-cover composition and streamlength produced dramatic changes in risk across subwatersheds in some cases. Comparison of the ' cases of no in-stream decay and homogeneously forested subwatersheds with extant conditions indicated that complete forest cover produced greater reductions in nutrient export risk than a high in-stream decay rate, especially for P. High rates of in-stream decay and complete forest cover produced approximately equivalent reductions in N export risk for downstream subwatersheds.

  • Citation: Wickham, James D.; Wade, Timothy G.; Riitters, Kurt H.; O’Neill, R.V.; Smith, Jonathan H.; Smith, Elizabeth R.; Jones, K.B.; Neale, A.C. 2003. Upstream-to-downstream changes in nutrient export risk. Landscape Ecology 18:195-208
  • Keywords: Chesapeake Bay, in-stream nutrient decay, modeling, nitrogen, phosphorus, pollution, watersheds
  • Posted Date: April 1, 1980
  • Modified Date: August 22, 2006
  • Print Publications Are No Longer Available

    In an ongoing effort to be fiscally responsible, the Southern Research Station (SRS) will no longer produce and distribute hard copies of our publications. Many SRS publications are available at cost via the Government Printing Office (GPO). Electronic versions of publications may be downloaded, printed, and distributed.

    Publication Notes

    • This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.
    • Our online publications are scanned and captured using Adobe Acrobat. During the capture process some typographical errors may occur. Please contact the SRS webmaster if you notice any errors which make this publication unusable.
    • To view this article, download the latest version of Adobe Acrobat Reader.