2013
DOI: 10.5194/bg-10-8013-2013
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Upland streamwater nitrate dynamics across decadal to sub-daily timescales: a case study of Plynlimon, Wales

Abstract: Abstract. Streamwater nitrate dynamics in the River Hafren, Plynlimon, mid-Wales were investigated over decadal to sub-daily timescales using a range of statistical techniques. Long-term data were derived from weekly grab samples and high-frequency data from 7-hourly samples (2007)(2008)(2009)) both measured at two sites: a headwater stream draining moorland and a downstream site below plantation forest. This study is one of the first to analyse upland streamwater nitrate dynamics across such a wide range of … Show more

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Cited by 42 publications
(37 citation statements)
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References 85 publications
(112 reference statements)
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“…In the case of nitrogen compounds, their concentrations are clearly affected by the biological activity of the catchment. This is because during the growing period, nitrogen is assimilated by plants and the concentrations of its compounds are significantly lower, which is confirmed by other studies (Gardner and McGlynn 2009;Halliday et al 2013). In turn, higher concentrations of nitrogen compounds are observed in autumn and winter, when the biological activity is definitely lower.…”
Section: Discussionsupporting
confidence: 80%
“…In the case of nitrogen compounds, their concentrations are clearly affected by the biological activity of the catchment. This is because during the growing period, nitrogen is assimilated by plants and the concentrations of its compounds are significantly lower, which is confirmed by other studies (Gardner and McGlynn 2009;Halliday et al 2013). In turn, higher concentrations of nitrogen compounds are observed in autumn and winter, when the biological activity is definitely lower.…”
Section: Discussionsupporting
confidence: 80%
“…For instance, we estimated that spring diel NO − 3 variation may reduce catchment NO − 3 exports by ~70 g N/ha (~16%) at the Ichetucknee River (770 km 2 , 8900 L/s), based on mean daily minima and maxima NO − 3 concentrations (0.38 and 0.46 mg N/L) reported by Heffernan and Cohen ( 2010 ). The contribution of fi nescale N dynamics to reduce catchment N export was even larger at the Upper Hafren River in UK (122 ha, 60 L/s), an open stream where spring diel NO − 3 variations (from 0.14 to 0.18 mg N/L) reduced stream NO − 3 loads by 154 g N/ha (22%) (Halliday et al 2013 ). These back-of-the-envelope calculations highlight that fi ne-scale N dynamics can not only indicate the preferential mechanisms of in-stream N uptake, but also provide a relevant evaluation of their contribution on regulating NO − 3 downstream fl uxes at the catchment scale.…”
Section: Discussionmentioning
confidence: 92%
“…The infl uence of fi ne-scale N patterns on N fl uxes could be even higher in open-canopy and lowland streams for which reported diel NO − 3 variations are larger than for headwater forested streams (Grimm 1987, Heffernan et al 2010, Halliday et al 2013. For instance, we estimated that spring diel NO − 3 variation may reduce catchment NO − 3 exports by ~70 g N/ha (~16%) at the Ichetucknee River (770 km 2 , 8900 L/s), based on mean daily minima and maxima NO − 3 concentrations (0.38 and 0.46 mg N/L) reported by Heffernan and Cohen ( 2010 ).…”
Section: Discussionmentioning
confidence: 98%
“…Despite being more time-consuming and characterized by some degree of subjectivity, manual calibration helps reduce the risk of considering parameter sets that fit the calibration data but lead to poor internal consistency in model response (Boyle et al, 2000;Fatichi et al, 2015;Moradkhani & Sorooshian, 2008). The model was run more than 200 times with different sets of parameters, which were varied over ranges suggested by literature (Table 2) (e.g., Bell, 2005;Benettin et al, 2015b;Brandt et al, 2004;Halliday et al, 2013;Kirby et al, 1997;Shand et al, 2005). The different parameter combinations were tested in each model run and the parameter sets which resulted in higher performance measures and physically plausible simulations of the simulated variables (e.g., amount of groundwater seepage or mean basin saturation) were then (Criss & Winston, 2008) for discharge.…”
Section: Model Setup Calibration and Confirmationmentioning
confidence: 99%