Phosphorus Loss from an Agricultural Watershed as a Function of Storm Size
- Andrew N. Sharpley *a,
- Peter J. A. Kleinmanb,
- A. Louise Heathwaitec,
- William J. Gburekd,
- Gordon J. Folmarb and
- John P. Schmidtb
- a Dep. of Crop, Soil and Environmental Sciences, 115 Plant Sciences Building, Univ. of Arkansas, Fayetteville, AR 72701
b USDA-ARS, Pasture Systems and Watershed Management Research Unit, Building 3702, Curtin Road, University Park, PA 16802-3702
c Centre for Sustainable Water Management, Lancaster Environment Centre, Lancaster Univ., Lancaster, LA1 4YQ, UK
d USDA-ARS, Pasture Systems and Watershed Management Research Unit, Building 3702, Curtin Road, University Park, PA 16802-3702. Mention of trade names does not imply endorsement by the U.S. Government
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.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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