Abstract
Hydrological variations hold a significant influence over the water chemistry in the karstic critical zone. In this context, the karstic Baget Catchment (BC) has been monitored at a high resolution over two years at the outlet in order to set up a typology of the flood events. The objective was to assess the multiple streamwater physicochemical patterns in response to hydrological variations, streamflow component (quick‐response, subsurface, and baseflow) and lithological contributions, and biogeochemical processes. The karstic catchment exhibited an impulsive response to flood events in relation to the typical structural and morphological characteristics of the karst. In addition, this response was constrained by the magnitude of the rainfall and the preceding hydroclimatic conditions. The variability of the dissolved load in streamflow was closely associated with the characteristics of the weathered rocks and the hydrological conditions throughout the year. Two simple indicators al-low to characterize the concentration–discharge relationships with different hysteresis patterns on a set of floods with various intensities and shapes of the hydrograph and under different hydrological conditions before the flood. Almost all elements exhibited either clockwise loops or more complex behaviors, suggesting a higher overall concentration when the major water contribution comes from the quick‐response flow (karst and surface runoff fraction). Besides, the epikarst flushing under dry conditions led counterclockwise hysteresis patterns for calcium (Ca2+) and bicarbonate (HCO3−) which revealed an overall chemostatic behavior as a result of carbonate dissolution in the karst. On the contrary, sulfate (SO42−) exhibited the widest relative variation during flooding and showed a significant sensitivity to the dilution process with increasing discharge. For medium flood episodes (Qmax < 4.4 m3∙s−1), an overall concentration increase or chemostatic behavior could be observed during the rising limb of the hydrograph. On the opposite, under extreme flood episodes (Qmax > 8.3 m3∙s−1) occurring after several rain events, a dilution pattern was noted for all elements originating from rock weathering. Finally, high‐frequency sampling during storm events improved the understanding of the factors controlling the hydrochemical dynamic in karstic catchments.
| Original language | English |
|---|---|
| Article number | 1818 |
| Pages (from-to) | 1-25 |
| Number of pages | 25 |
| Journal | Water (Switzerland) |
| Volume | 13 |
| Issue number | 13 |
| DOIs | |
| Publication status | Published - 1 Jul 2021 |
| Externally published | Yes |
Bibliographical note
Funding Information:Funding: This research was funded by the CNRS INSU through the IR OZCAR and the SNO KARST and by the CNRS‐INEE through an annual allocation and through the LTSER platform ZA PYGAR.
Funding Information:
This research was funded by the CNRS INSU through the IR OZCAR and the SNO KARST and by the CNRS?INEE through an annual allocation and through the LTSER platform ZA PYGAR. Acknowledgments: The authors are particularly grateful for the support from SNO KARST, IR OZ? CAR, CNRS?INEE, CNRS?INSU and Zone Atelier Pyr?n?es?Garonne (LTSER ZA PYGAR). The data of this research were collected and partly monitored under the initiative of the French KARST Observatory Network SNO KARST (www.sokarst.org) initiative of the INSU/CNRS, whose purpose is to reinforce the exchange of knowledge and encourage interdisciplinary research on karst systems. The SNO Karst is also a member of the French Research Infrastructure OZCAR, the French network of Critical Zone Observatories. The authors thank S. Beranger from BRGM?Occitanie for facilitating the access to part of the discharge data from the ADES database. Special thanks are given to B. Chaumet, C. Pautot, V. Payre?Suc and M.J. Tavella for their help in the field samplings and/or lab works. The analytical platforms of the Laboratory of Functional Ecology and Environment, PAPC (V. Payre?Suc, F. Julien, D. Lambrigot, and W. Amblas) and the chemical laboratory department of the GET (C. Causserand and P. Besson) make a significant contribution to the analytical work. F. Ulloa?Cedamanos?s PhD was financed by a fellowship from the French Ministry of Higher Educa-tion, Research and Innovation.
Funding Information:
Acknowledgments: The authors are particularly grateful for the support from SNO KARST, IR OZ‐ CAR, CNRS‐INEE, CNRS‐INSU and Zone Atelier Pyrénées‐Garonne (LTSER ZA PYGAR). The data of this research were collected and partly monitored under the initiative of the French KARST Ob‐ servatory Network SNO KARST (www.sokarst.org) initiative of the INSU/CNRS, whose purpose is to reinforce the exchange of knowledge and encourage interdisciplinary research on karst systems. The SNO Karst is also a member of the French Research Infrastructure OZCAR, the French network of Critical Zone Observatories. The authors thank S. Beranger from BRGM‐Occitanie for facilitating the access to part of the discharge data from the ADES database. Special thanks are given to B. Chaumet, C. Pautot, V. Payre‐Suc and M.J. Tavella for their help in the field samplings and/or lab works. The analytical platforms of the Laboratory of Functional Ecology and Environment, PAPC (V. Payre‐Suc, F. Julien, D. Lambrigot, and W. Amblas) and the chemical laboratory department of the GET (C. Causserand and P. Besson) make a significant contribution to the analytical work. F. Ulloa‐Cedamanos’s PhD was financed by a fellowship from the French Ministry of Higher Educa‐ tion, Research and Innovation.
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