Fabre et al. (2026) Integrated modelling of sediment and organic carbon fluxes in a large catchment: quantifying riverine contributions to the Mediterranean Sea

Identification

• Journal: CATENA
• Year: 2026
• Authors: Clément Fabre, Yoann Copard, S. Sauvage, Olivier Radakovitch, Hervé Piegay, José Miguel Sánchez-Pérez, Mathieu Fressard, Thomas Faraon
• DOI: 10.1016/j.catena.2026.109794

Research Groups

• Tour du Valat, Research Institute for the Conservation of Mediterranean Wetlands, Arles, France.
• Centre de Recherche sur la Biodiversité et l'Environnement (CRBE), Université de Toulouse, CNRS, Toulouse, France.
• Morphodynamique Continentale et Côtière (M2C), CNRS, Univ Rouen Normandie, Caen, France.
• Autorité de sûreté nucléaire et de radioprotection (ASNR), Saint-Paul-lez-Durance, France.
• Environnement Ville Société (EVS), CNRS, ENS Lyon, University of Lyon, France.
• IDEES, CNRS, Normandie Univ, UNICAEN, Caen, France.

Short Summary

This study utilizes the SWAT-C model to quantify the integrated fluxes of sediment, particulate organic carbon (POC), and dissolved organic carbon (DOC) from the Rhone River catchment to the Mediterranean Sea between 2002 and 2020. The research identifies the Durance and Isère rivers as primary sediment contributors and characterizes the exported organic carbon as predominantly labile POC and refractory DOC.

Objective

• To quantify the spatiotemporal dynamics of dissolved and particulate organic carbon (DOC, POC) and sediment fluxes in the Rhone River catchment.
• To evaluate the performance and limitations of the SWAT-C model in a large, anthropogenically pressured Mediterranean basin.

Study Configuration

• Spatial Scale: The Rhone River catchment, covering approximately 97,800 km² across Switzerland and France (focusing on the 90% French portion).
• Temporal Scale: 2002–2020, utilizing a monthly time-step for flux estimation.

Methodology and Data

• Models used: SWAT-C (Soil and Water Assessment Tool – Carbon), a semi-distributed model adapted to simulate terrestrial and aquatic carbon cycles.
• Data sources:
  • Topography/Land Use: BD Alti (25 m DEM), Corine Land Cover 2012.
  • Soils: Harmonised World Soil Database (HWSD) v 2.0.
  • Climate: SAFRAN (Météo France) daily meteorological data (8 km resolution).
  • Hydrometric/Biogeochemical: Rhone Sediment Observatory (OSR) for high-frequency sediment and POC; NAIADES database for DOC; HydroPortail and BAFU for river discharge.
  • Infrastructure: French Committee for Dams and Reservoirs database for dam operations.

Main Results

• Average Annual Exports: The Rhone delivers approximately 5.52 ± 1.81 Mt y⁻¹ of sediment, 78.8 ± 51.0 kt y⁻¹ of POC, and 95.1 ± 22.0 kt y⁻¹ of DOC to the Mediterranean Sea.
• Hydrological Influence: High discharge events (above the 75th percentile) account for 54.4% of sediment, 71.5% of POC, and 44.3% of DOC total exports.
• Organic Carbon Quality: At the Rhone outlet, the proportions of labile vs. refractory organic carbon are 85/15 for POC and 5/95 for DOC.
• Spatial Contributions: The southern sub-basins (Durance, Ardèche, Gardon) are significant contributors to POC and DOC fluxes, while the northern basins (Saône, Ain) provide more stable DOC leaching.
• Model Performance: SWAT-C demonstrated good performance for hydrology (NSE = 0.75) and sediment at the outlet, though it faced challenges in capturing high-frequency peaks and regionalizing in-stream OC parameters.

Contributions

• Provides the first catchment-scale integrated modelling of organic carbon fluxes for the Rhone River, the primary supplier of terrestrial matter to the Western Mediterranean.
• Demonstrates the applicability of SWAT-C for large-scale biogeochemical studies while highlighting the need for improved spatial parameterization of in-stream carbon processes.
• Quantifies the specific contributions of major tributaries (e.g., Durance, Isère, Saône) to the total carbon budget of the Mediterranean Sea.

Funding

• MOOSE program (Mediterranean Oceanic Observing System for the Environment), sponsored by Alliance Allenvi and CNRS-INSU.
• Agence de l'Eau Rhône-Méditerranée et Corse.
• Rhone Sediment Observatory (OSR) program, funded via the Plan Rhône (European Regional Development Fund - ERDF).
• Compagnie Nationale du Rhône (CNR) and Électricité de France (EDF).
• Regional councils of Auvergne-Rhône-Alpes, PACA, and Occitanie.

Citation

@article{Fabre2026Integrated,
  author = {Fabre, Clément and Copard, Yoann and Sauvage, S. and Radakovitch, Olivier and Piegay, Hervé and Sánchez-Pérez, José Miguel and Fressard, Mathieu and Faraon, Thomas},
  title = {Integrated modelling of sediment and organic carbon fluxes in a large catchment: quantifying riverine contributions to the Mediterranean Sea},
  journal = {CATENA},
  year = {2026},
  doi = {10.1016/j.catena.2026.109794},
  url = {https://doi.org/10.1016/j.catena.2026.109794}
}

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