Preprints
https://doi.org/10.5194/hess-2022-132
https://doi.org/10.5194/hess-2022-132
 
20 Apr 2022
20 Apr 2022
Status: this preprint is currently under review for the journal HESS.

Seasonal δ2H and δ18O changes in river water from a high-altitude humid plain of the southern Alps (Cervières, France): tracking the transit time through a watershed

Christoph Lécuyer1, François Atrops1, François Fourel2, Jean-Pierre Flandrois3, Gilles Pinay4, and Philippe Davy5 Christoph Lécuyer et al.
  • 1Univ Lyon, UCBL, ENSL, UJM, CNRS, LGL-TPE, F-69622, Villeurbanne, France
  • 2Laboratoire d'Ecologie des Hydrosystèmes Naturels et Anthropisés, CNRS UMR 5023, Université Claude Bernard, Lyon 1, France
  • 3LBBE, CNRS UMR5558, Univ Lyon, Univ Lyon 1, 43 bd du 11 Novembre 1918, 69622 Villeurbanne, France
  • 4UMR 5600 Environnement, Ville, Société, Campus Descartes ENS Lyon, France
  • 5Géosciences Rennes, CNRS UMR 6118, OSUR, Campus de Beaulieu, Université de Rennes 1, 35042 Rennes, France

Abstract. The Alps Mountains play a major role in the water cycle at a regional scale in Europe. This mountain range acts as the ‘water tower’ of Europe by storing large volumes of ice and snow, and by regulating the runoff of the rivers constituting freshwater reservoirs of paramount importance for the biodiversity and human activity. Located in the French Southern Alps, the Cerveyrette valley and a high-altitude (≈ 2000 m) swampy plain constitute a watershed of about 100 km2. From August 2011 to July 2013, water samples were collected monthly from the Cerveyrette river upstream of the Cervières village (elevation = 1620 m) located in the Upper Durance catchment area. Apparent cyclicality in δ2H and δ18O of the river waters documented over these two years partly reflect seasonal variations in the isotopic compositions of precipitations that mainly occur as snow accumulating at altitudes ranging from ≈ 1700 m to 3300 m. The estimated time lag of three to four months between summer precipitations and their sampling in the Cerveyrette river at the discharge point of the watershed is interpreted to integrate both the mean transfer time of the water discharge and the rate of melting of the snow cover. Here, we show that the transfer time from mountain-accumulated snow toward the low-altitude cultivated areas (Provence) is a sensitive key variable responding to the current climate warming. Indeed, a lowering of the snow cover surface is expected to reduce the buffer effect of snow compared to rainfall, and to decrease the time period during which the discharge rate of the Durance river is large enough for constituting sizable water resources. Understanding and modeling water transit times in nival dominated watersheds are consequently critical to evaluate the impact of the ongoing climate warming on water circulation and resources in the Alps and downstream including the case of mitigation actions.

Christoph Lécuyer et al.

Status: open (until 15 Jun 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on hess-2022-132', Anonymous Referee #1, 18 May 2022 reply
  • RC2: 'Comment on hess-2022-132', Anonymous Referee #2, 20 May 2022 reply

Christoph Lécuyer et al.

Christoph Lécuyer et al.

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Short summary
Located in the French Southern Alps, the Cerveyrette valley constitutes a watershed of about 100 km2. Cyclicality in the stable isotope compositions of the river waters recorded over two years allowed us to estimate a time lag of three to four months between precipitations and their sampling at the discharge point of the watershed. We thus show that the transfer time from mountain-accumulated snow toward the low-altitude areas is a sensitive variable responding to the current climate warming.