TY - JOUR
T1 - Nitrate removal and young stream water fractions at the catchment scale
AU - Benettin, Paolo
AU - Fovet, Ophélie
AU - Li, Li
N1 - Funding Information:
The Kervidy‐Naizin catchment belongs to the AgrHyS Observatory ( https://www6.inrae.fr/ore_agrhys_eng ), one of the French Critical Zone Observatories (OZCAR). P. B. thanks ENAC School at EPFL for financial support. L. L. acknowledges stimulating discussions with the ECHO Lab during her sabbatical year at EPFL. The authors also thank Yannick Fauvel for providing preliminary data of chloride in precipitation and Laura Garbaccio for help with initial model setup.
Funding Information:
The Kervidy-Naizin catchment belongs to the AgrHyS Observatory (https://www6.inrae.fr/ore_agrhys_eng), one of the French Critical Zone Observatories (OZCAR). P. B. thanks ENAC School at EPFL for financial support. L. L. acknowledges stimulating discussions with the ECHO Lab during her sabbatical year at EPFL. The authors also thank Yannick Fauvel for providing preliminary data of chloride in precipitation and Laura Garbaccio for help with initial model setup.
Publisher Copyright:
© 2020 John Wiley & Sons Ltd
PY - 2020/6/15
Y1 - 2020/6/15
N2 - Despite extensive research on nitrate export and removal, nutrient contamination remains a major threat to water bodies worldwide. At the local scale, nitrate removal is governed by biogeochemical conditions that vary in space and time, making integration to entire landscapes critical. Water transit times have often been used to describe solute transport, but the relation between water age and nitrate removal at the catchment scale is still poorly understood. We test the hypothesis that nitrate removal peaks when the fraction of young water in discharge is at its minimum, because nitrate removal occurs mostly under dry conditions where deeper, older groundwater dominates streamflow. We tested this hypothesis by exploring a detailed water quality record from the Kervidy–Naizin catchment (FR) and comparing the dynamics of nitrate to those of a conservative solute (chloride). We find that estimates of nitrate removal are consistent with previous estimates at the site and they show a good (inverse) correlation with the fraction of streamflow that is younger than 2.5 months. However, this young water fraction cannot be used to predict nitrate removal in the winter–spring period, when no removal is observed regardless of streamflow age. While this leads us to reject our hypothesis during the winter period, it also suggests that water age distributions and their correlation with nitrate removal can possibly reveal distinct sources of stream water at different hydrologic regimes and relevant biogeochemical reactions.
AB - Despite extensive research on nitrate export and removal, nutrient contamination remains a major threat to water bodies worldwide. At the local scale, nitrate removal is governed by biogeochemical conditions that vary in space and time, making integration to entire landscapes critical. Water transit times have often been used to describe solute transport, but the relation between water age and nitrate removal at the catchment scale is still poorly understood. We test the hypothesis that nitrate removal peaks when the fraction of young water in discharge is at its minimum, because nitrate removal occurs mostly under dry conditions where deeper, older groundwater dominates streamflow. We tested this hypothesis by exploring a detailed water quality record from the Kervidy–Naizin catchment (FR) and comparing the dynamics of nitrate to those of a conservative solute (chloride). We find that estimates of nitrate removal are consistent with previous estimates at the site and they show a good (inverse) correlation with the fraction of streamflow that is younger than 2.5 months. However, this young water fraction cannot be used to predict nitrate removal in the winter–spring period, when no removal is observed regardless of streamflow age. While this leads us to reject our hypothesis during the winter period, it also suggests that water age distributions and their correlation with nitrate removal can possibly reveal distinct sources of stream water at different hydrologic regimes and relevant biogeochemical reactions.
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U2 - 10.1002/hyp.13781
DO - 10.1002/hyp.13781
M3 - Article
AN - SCOPUS:85085122960
VL - 34
SP - 2725
EP - 2738
JO - Hydrological Processes
JF - Hydrological Processes
SN - 0885-6087
IS - 12
ER -