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Journal of Environmental Quality Abstract - Landscape and Watershed Processes

Quantifying Phosphorus Retention and Release in Rivers and Watersheds Using Extended End-Member Mixing Analysis (E-EMMA)


This article in JEQ

  1. Vol. 40 No. 2, p. 492-504
    Received: June 29, 2010

    * Corresponding author(s): hpj@ceh.ac.uk
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  1. Helen P. Jarvie *a,
  2. Colin Neala,
  3. Paul J.A. Withersb,
  4. David B. Bakerc,
  5. R. Peter Richardsc and
  6. Andrew N. Sharpleyd
  1. a Centre for Ecology & Hydrology, Maclean Building, Crowmarsh Gifford, Wallingford, Oxfordshire OX10 8BB UK
    b School of Environment, Natural Resources and Geography, Bangor Univ., Bangor, Gwynedd LL57 2UW UK
    c National Center for Water Quality Research, Heidelberg Univ., 310 E. Market St., Tiffin, OH 44883-2462
    d Dep. of Crop, Soil and Environmental Sciences, 115 Plant Science Building, Univ. of Arkansas, Fayetteville, AR 72701. Assigned to Associate Editor David Nash


Extended end-member mixing analysis (E-EMMA) is presented as a novel empirical method for exploring phosphorus (P) retention and release in rivers and watersheds, as an aid to water-quality management. E-EMMA offers a simple and versatile tool that relies solely on routinely measured P concentration and flow data. E-EMMA was applied to two river systems: the Thames (U.K.) and Sandusky River (U.S.), which drain similar watershed areas but have contrasting dominant P sources and hydrology. For both the Thames and Sandusky, P fluxes at the watershed outlets were strongly influenced by processes that retain and cycle P. However, patterns of P retention were markedly different for the two rivers, linked to differences in P sources and speciation, hydrology and land use. On an annual timescale, up to 48% of the P flux was retained for the Sandusky and up to 14% for the Thames. Under ecologically critical low-flow periods, up to 93% of the P flux was retained for the Sandusky and up to 42% for the Thames. In the main River Thames and the Sandusky River, in-stream processes under low flows were capable of regulating the delivery of P and modifying the timing of delivery in a way that may help to reduce ecological impacts to downstream river reaches, by reducing ambient P concentrations at times of greatest river eutrophication risk. The results also suggest that by moving toward cleaner rivers and improved ecosystem health, the efficiency of P retention may actually increase.

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Copyright © 2011. American Society of Agronomy, Crop Science Society of America, Soil Science SocietyAmerican Society of Agronomy, Crop Science Society of America, and Soil Science Society of America