Preprints
https://doi.org/10.5194/hess-2021-267
https://doi.org/10.5194/hess-2021-267

  31 May 2021

31 May 2021

Review status: this preprint is currently under review for the journal HESS.

 Identification of the contributing area to river discharge during low-flow period

Maxime Gillet1,2, Corinne Le Gal La Salle1, Pierre Alain Ayral2,3, Somar Khaska1, Philippe Martin3, and Patrick Verdoux1 Maxime Gillet et al.
  • 1Université de Nîmes, unité de recherche Chrome France, F-30021 Nîmes Cedex 1
  • 2Hydrosciences Montpellier, Univ. Montpellier, IMT Mines Ales, IRD, CNRS, Ales, France
  • 3UMR 7 300 Espace CNRS, Université d’Avignon France

Abstract. The increasing severity of hydrological droughts in the Mediterranean basin related to climate change raises the need to understand the processes sustaining low-flow. The purpose of this paper is to trial simple mixing model approaches first to identify and then quantify streamflow contribution during low-water periods. An approach based on the coupling of geochemical data with hydrological data allows quantifying flow contributions. In complement, monitoring during the low water period was used to investigate the drying up the trajectory of each geological reservoir individually. Data were collected during the summer of 2018 and 2019 on a Mediterranean river (Gardon de Sainte Croix). The identification of the end-members was performed after the identification of groundwater geochemical signature clustered according to the geological nature of the reservoir. Two complementary methods validate further the characterisation: rock leaching experiments and unsupervised classification (k-means). The use of G-EMMA mixing model coupled with hydrological monitoring of the main river discharge rate shows major disparities in the contribution of the geological units, showing a reservoir with a minor contribution in high flow becoming preponderant during the low-flow period. This finding revealed to be of the utmost importance for managing water resources during the dry period.

Maxime Gillet et al.

Status: open (until 26 Jul 2021)

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Maxime Gillet et al.

Maxime Gillet et al.

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Short summary
This paper aims at identifying the key reservoirs sustaining river low flow during dry summer. The reservoirs are discriminated based on the geological nature of the formations and on the geochemical signature of groundwater. Results show the increasing importance to low-flow support of a specific reservoir, showing only a limited outcrop area, and becoming preponderant in the heart of the dry season. This finding will contribute to improve the protective measures for preserving of low.