Preprints
https://doi.org/10.5194/egusphere-2024-2737
https://doi.org/10.5194/egusphere-2024-2737
19 Sep 2024
 | 19 Sep 2024

Are rivers becoming more intermittent in France? Learning from an extended set of climate projections based on the Coupled Model Intercomparison Project phase 5 (CMIP5)

Tristan Jaouen, Lionel Benoit, Louis Héraut, and Eric Sauquet

Abstract. This study aims to assess the changes in the intermittency of river flows across France in the context of climate change. Projection of flow intermittence are derived from the results of the Explore2 project, which is the latest national study that proposes a wide range of potential hydrological futures for the 21st century. The multi-model approach developed within the Explore2 project enable to characterize uncertainties in future flow intermittence. Combined with discrete observations of flow states, hydrological projections are post-processed to compute the daily probability of flow intermittency (PFI) on each element of the partition of France in hydroecoregions (HER2).

The post-processing consists of calibrating logistic regressions between the historical flow states of the Observatoire National des Étiages (ONDE) network and the flow data simulated by the hydrological models (HMs) involved in Explore2 projected with the Safran reanalysis as inputs. After calibration, these regressions are used to project daily PFIs for the whole of the 21st century, based on flow simulations from five HMs driven by up to 17 climate projections under RCP 2.6, 4.5, and 8.5 climate change scenarios.

The results show good agreement among the HMs regarding the increase in flow intermittency under RCP 4.5 and 8.5. The changes in mean daily PFI between July and October, and the shifts in the first and last days when PFI exceeds 20 %, suggest a gradual intensification and extension of dry spells throughout the century. The southern regions of France are likely to experience greater increases in runoff intermittency than the northern regions. Uncertainty is greater in northern France, due to the variability of rainfall. Mountainous regions such as the Alps and the Pyrenees are likely to experience changes in the dynamics of snowmelt and groundwater recharge, which could lead to changes in their runoff regimes.

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Tristan Jaouen, Lionel Benoit, Louis Héraut, and Eric Sauquet

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-2737', Anonymous Referee #1, 30 Oct 2024
  • RC2: 'Comment on egusphere-2024-2737', Anonymous Referee #2, 11 Nov 2024
Tristan Jaouen, Lionel Benoit, Louis Héraut, and Eric Sauquet

Data sets

Explore2 Eric Sauquet et al. https://entrepot.recherche.data.gouv.fr/dataverse/explore2

Model code and software

PostDocINRAE Jaouen Tristan https://github.com/tjaouen/PostDocINRAE

Tristan Jaouen, Lionel Benoit, Louis Héraut, and Eric Sauquet

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Short summary
This study uses a multi-model approach to assess future changes in river flow intermittency across France under climate change. Combining projections from the Explore2 project with historical flow observations, logistic regressions estimate daily probabilities of flow intermittency (PFI) under RCP 2.6, 4.5, and 8.5 scenarios. Results suggest intensifying and prolonged dry spells throughout the 21st century, with southern France more affected, while uncertainty remains higher in northern regions.