Journal
JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES
Volume 122, Issue 9, Pages 2265-2281Publisher
AMER GEOPHYSICAL UNION
DOI: 10.1002/2017JG003904
Keywords
sensor; in situ; NO3; DOC; river; hysteresis
Funding
- Leverhulme Trust [IN-2013-042]
- UK Natural Environment Research Council [NERC NE/L003872/1]
- University of Birmingham
- Birmingham Institute of Forest Research (BIFoR) [28]
- JABBS Foundation
- Natural Environment Research Council [NE/L003872/1, 1602135] Funding Source: researchfish
- NERC [NE/L003872/1] Funding Source: UKRI
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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 8month 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.
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