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Title: Hydrological versus biogeochemical controls on catchment nitrate export: A test of the flushing mechanism Authored by: Ocampo, C.J., Oldham,C.E., Sivapalan, M. and Turner, J.F. Abstract:
Deciphering the connection between streamflows and nitrate (NO-3) discharge requires identification of the various water flow pathways within a catchment, and the different time-scales at which hydrological and biogeochemical processes occur. Despite the complexity of the processes involved, many catchments around the world present a characteristic flushing response of NO-3 export. Yet the controls on the flushing response, and how they vary across space and time, are still not clearly understood. In this paper, the flushing response of NO-3 export from a rural catchment in Western Australia was investigated using isotopic (deuterium), chemical (chloride, NO-3), and hydrometric data across different antecedent conditions and time-scales. The catchment streamflow was at all time-scales dominated by a pre-event water source, and the NO-3 discharge was correlated with the magnitude of areas contributing to saturation overland flow. The NO-3 discharge also appeared related to the shallow groundwater dynamics. Thus, the antecedent moisture condition of the catchment at seasonal and interannual time-scales had a major impact on the NO-3 flushing response. In particular, the dynamics of the shallow ephemeral perched aquifer drove a shift from hydrological controls on NO-3 discharge during the early flushing stage to an apparent biogeochemical control on NO-3 discharge during the steady decline stage of the flushing response. This temporally variable control hypothesis provides a new and alternative description of the mechanisms behind the commonly seen flushing response. Copyright © 2006 John Wiley & Sons, Ltd.
Reference: Ocampo, C.J., Oldham,C.E., Sivapalan, M. and Turner, J.F., 2006, Hydrological versus biogeochemical controls on catchment nitrate export: A test of the flushing mechanism, 20 (20): 4269-4286 Keywords: hydrology • streamflow generation • runoff sources • biogeochemistry • nitrate flushing |
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