Phosphorus loss from an agricultural watershed as a function of storm size

Andrew N. Sharpley, Peter J.A. Kleinman, A. Louise Heathwaite, William J. Gburek, Gordon J. Folmar, John P. Schmidt

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127 Scopus citations


Phosphorus (P) loss from agricultural watersheds is generally greater in storm rather than base flow. Although fundamental to P-based risk assessment tools, few studies have quantified the effect of storm size on P loss. Thus, the loss of P as a function of flow type (base and storm flow) and size was quantified for a mixed-land use watershed (FD-36; 39.5 ha) from 1997 to 2006. Storm size was ranked by return period (<1, 1-3, 3-5, 5-10, and >10 yr), where increasing return period represents storms with greater peak and total flow. From 1997 to 2006, storm flow accounted for 32% of watershed discharge yet contributed 65% of dissolved reactive P (DP) (107 g ha-1 yr -1) and 80% of total P (TP) exported (515 g ha-1 yr -1). Of 248 storm flows during this period, 93% had a return period of <1 yr, contributing most of the 10-yr flow (6507 m3 ha -1; 63%) and export of DP (574 g ha-1; 54%) and TP (2423 g ha-1; 47%). Two 10-yr storms contributed 23% of P exported between 1997 and 2006. A significant increase in storm flow DP concentration with storm size (0.09-0.16 mg L-1) suggests that P release from soil and/or area of the watershed producing runoff increase with storm size. Thus, implementation of P-based Best Management Practice needs to consider what level of risk management is acceptable.

Original languageEnglish (US)
Pages (from-to)362-368
Number of pages7
JournalJournal of Environmental Quality
Issue number2
StatePublished - Mar 2008

All Science Journal Classification (ASJC) codes

  • Environmental Engineering
  • Water Science and Technology
  • Waste Management and Disposal
  • Pollution
  • Management, Monitoring, Policy and Law


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