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Keywords:

  • agricultural catchment;
  • storm-events;
  • suspended sediment;
  • dissolved and particulate organic carbon;
  • nitrates;
  • hysteresis

Abstract

The temporal variability of suspended sediment, nitrates (NO3) and dissolved (DOC) and particulate organic carbon concentrations was analysed in the Alegria agricultural watershed over a 2-year period. Nine storm events were studied, including an exhaustive analysis of hydrometeorological conditions, quantification of fluxes, and concentration-discharge hysteresis loop characterization. The overall aim was to study the variability in these components during storm events and determine the mechanisms (flow paths) affecting the trajectories, from the source to the stream. The forms, rotational patterns and trends of hysteretic loops were investigated, and relationships between hysteresis features and hydrological parameters were studied. The results revealed clear differences between particulate (suspended sediment, particulate organic carbon) and dissolved (DOC, NO3) matter transport responses. Movement of the particulate matter was attributed to surface water, as reflected in clockwise hysteresis loops, whereas dissolved matter showed, in general, counterclockwise hysteresis loops, indicating a time delay in the arrival of solutes to the stream. This could be related to subsurface flow paths for DOC and a groundwater source for NO3. Copyright © 2013 John Wiley & Sons, Ltd.