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High-frequency monitoring of catchment nutrient exports reveals highly variable storm event responses and dynamic source zone activation

Research output: Contribution to journalArticle

  • Phillip J. Blaen
  • Kieran Khamis
  • Charlotte Lloyd
  • Sophie Comer-Warner
  • Francesco Ciocca
  • Rick M. Thomas
  • A. Rob MacKenzie
  • Stefan Krause
Original languageEnglish
Pages (from-to)2265-2281
Number of pages17
JournalJournal of Geophysical Research: Biogeosciences
Volume122
Issue number9
Early online date7 Sep 2017
DOIs
DateAccepted/In press - 25 Aug 2017
DateE-pub ahead of print - 7 Sep 2017
DatePublished (current) - 2017

Abstract

Storm events can drive highly variable behavior in catchment nutrient and water fluxes, yet short-term event dynamics are frequently missed by low-resolution sampling regimes. In addition, nutrient source zone contributions can vary significantly within and between storm events. Our inability to identify and characterize time-dynamic source zone contributions severely hampers the adequate design of land use management practices in order to control nutrient exports from agricultural landscapes. Here we utilize an 8 month high-frequency (hourly) time series of streamflow, nitrate (NO3-N), dissolved organic carbon (DOC), and hydroclimatic variables for a headwater agricultural catchment. We identified 29 distinct storm events across the monitoring period. These events represented 31% of the time series and contributed disproportionately to nutrient loads (42% of NO3-N and 43% of DOC) relative to their duration. Regression analysis identified a small subset of hydroclimatological variables (notably precipitation intensity and antecedent conditions) as key drivers of nutrient dynamics during storm events. Hysteresis analysis of nutrient concentration-discharge relationships highlighted the dynamic activation of discrete NO3-N and DOC source zones, which varied on an event-specific basis. Our results highlight the benefits of high-frequency in situ monitoring for characterizing short-term nutrient fluxes and unraveling connections between hydroclimatological variability and river nutrient export and source zone activation under extreme flow conditions. These new process-based insights, which we summarize in a conceptual model, are fundamental to underpinning targeted management measures to reduce nutrient loading of surface waters.

Additional information

2017JG003904

    Research areas

  • Nutrients and nutrient cycling, Water quality, Extreme events, Hydroclimatology, Monitoring networks, sensor, in situ, NO3, DOC, river, hysteresis

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    Rights statement: This is the final published version of the article (version of record). It first appeared online via WILEY at http://onlinelibrary.wiley.com/doi/10.1002/2017JG003904/abstract. Please refer to any applicable terms of use of the publisher.

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