Nitrate dynamics in a rural headwater catchment: measurements and modelling. Issue 4 (27th February 2013)

• Record Type: Journal Article
• Authors: Smethurst, Philip J.; Petrone, Kevin C.; Langergraber, Günter; Baillie, Craig C.; Worledge, Dale; Nash, David
• Is Part Of: Hydrological processes. Volume 28:Issue 4(2014:Feb.)
• Page Start: 1820
• Page End: 1834
• Publication Date: 2013-02-27
• Subjects: Hydrology -- Periodicals; Hydrology -- Research -- Periodicals; Hydrologic models -- Periodicals; Hydrological forecasting -- Periodicals; 631.432
• DOI: 10.1002/hyp.9709
• Languages: English
• ISSNs: 0885-6087

Abstract

<abstract abstract-type="main"> <title>Abstract</title> <p>This study was designed to improve our understanding of, and mechanistically simulate, nitrate (NO<sub>3</sub>) dynamics in a steep 9.8 ha rural headwater catchment, including its production in soil and delivery to a stream via surface and subsurface processes. A two‐dimensional modelling approach was evaluated for (1) integrating these processes at a hillslope scale annually and within storms, (2) estimating denitrification, and (3) running virtual experiments to generate insights and hypotheses about using trees in streamside management zones (SMZs) to mitigate NO<sub>3</sub> delivery to streams. Total flow was mathematically separated into quick‐ and slow‐flow components; the latter was routed through the HYDRUS software with a nitrogen module designed for constructed wetlands. Flow was monitored for two years. High surface‐soil NO<sub>3</sub> concentrations started to be delivered to the stream via preferential subsurface flow within two days of the storm commencing. Groundwater NO<sub>3</sub>‐N concentrations decreased from 1.0 to less than 0.1 mg l<sup>−1</sup> from up‐slope to down‐slope water tables, respectively, which was attributed to denitrification. Measurements were consistent with the flushing of NO<sub>3</sub> mainly laterally from surface soil during and following each storm. The model accurately accounted for NO<sub>3</sub> turnover, leading to the hypotheses that denitrification was a minor flux (<3 kg N ha<sup>−1</sup>) compared to uptake (98<sup>−</sup>127 kg N ha<sup>−1</sup>), and that SMZ trees would reduce denitrification if they lowered the water table. This research provides an example of the measurement and modelling of NO<sub>3</sub> dynamics at a small‐catchment scale with high spatial and temporal resolution. Copyright © 2013 John Wiley & Sons, Ltd.</p> </abstract>