Guilhen et al. (2025) Assessment of surface water storage in the Amazon floodplains by hydrological modelling and earth observation data

Identification

• Journal: Journal of Hydrology
• Year: 2025
• Date: 2025-12-12
• Authors: Jérémy Guilhen, Clément Fabre, Marie Parrens, Franck Mercier, Ahmad Al Bitar, Jean-Michel Martínez, J.M. Sánchez-Pérez
• DOI: 10.1016/j.jhydrol.2025.134758

Research Groups

• Universit´e de Toulouse, Toulouse INP, CNRS, IRD, CRBE, Toulouse, France
• Collecte Localisation Satellites, France
• Centre d’Etudes Spatiales de la Biosph`ere (CESBIO), CNES, Universit´e de Toulouse (UPS), Toulouse, France
• Dynafor, Universit´e de Toulouse, INRAE, INPT, INP-PURPAN, Castanet-Tolosan, France
• Institut de Recherche pour le D´eveloppement, Laboratoire GET (IRD, CNRS, UPS, CNES), Toulouse, France

Short Summary

This study quantifies the spatiotemporal dynamics of floodplain water storage in the Amazon Basin from 2000–2018 using an integrated framework of hydrological modeling and multi-sensor Earth observation data, revealing a mean annual surface water storage of 1800 ± 854 km³ with significant sub-basin contributions.

Objective

• To simulate floodplain–river exchange and water storage dynamics at daily temporal resolution using the SWAT-FP model over the period 2000–2018, evaluating results with discharge observations and satellite altimetry.
• To quantify seasonal and interannual variability in floodplain water storage and identify sub-basin contributions to basin-scale hydrological dynamics.

Study Configuration

• Spatial Scale: Amazon Basin (approximately 6.1 million km²)
• Temporal Scale: 2000–2018, with daily resolution

Methodology and Data

• Models used: Soil and Water Assessment Tool - Floodplain module (SWAT-FP)
• Data sources:
  • In situ observations: Discharge measurements from 8 gauging stations of the HyBam network.
  • Remote sensing:
    • L-band passive microwave observations from Soil Moisture and Ocean Salinity (SMOS) satellite (SWAF-HR dataset) for floodplain extent.
    • Altimetry data from Jason-2 (2009–2017), Jason-3 (2017–2019), and Sentinel-3A (2016–2019) for water surface elevation.
  • Input data for SWAT-FP:
    • SRTM DEM v3 (500 m spatial resolution)
    • HWSD soil layer (1 km spatial resolution)
    • GLC 2000 land use layer (1 km spatial resolution)
    • TRMM 3B42-v7 for precipitation (0.25° spatial resolution)
    • ERA-Interim for air temperatures (0.80° spatial resolution)

Main Results

• The SWAT-FP model demonstrated high skill, with a mean R² of 0.83 for discharge and R² > 0.62 for floodplain water surface elevation.
• The mean annual surface water storage in the Amazon Basin floodplains was estimated at 1800 ± 854 km³.
• The Negro and Madeira sub-basins were identified as the dominant contributors, accounting for approximately 480 km³ (33.6 %) and 312 km³ (12.5 %) of the total floodplain storage, respectively.
• Pronounced seasonal cycles were observed, with floods beginning in Andean tributaries (December-January), peaking in central floodplains (March-May), and in northern tributaries (May-September).
• Interannual stability of floodplain water storage was observed at the basin scale.
• Surface water storage accounted for approximately 63% of the terrestrial water storage anomaly in the Amazon Basin.
• The intense 2015-2016 El Niño episode caused a deficit of -607 km³ in the entire basin's floodplains.

Contributions

• Provides the first consistent long-term (2000–2018) quantification of Amazonian floodplain water storage dynamics at daily resolution.
• Develops a robust observational–modeling framework that integrates multi-sensor remote sensing with a process-based hydrological model (SWAT-FP) specifically improved for floodplain–river interactions.
• Emphasizes the critical role of floodplains in regulating basin-scale hydrological fluxes.
• Offers a framework for improving large-scale hydrological and Earth system models in tropical regions, with potential for future biogeochemical flux simulations.

Funding

• HydroSIM project (Hydrologie Spatiale, In situ et Mod´elisation)
• European Space Agency (ESA) Expert Support Laboratories
• Terre Oc´ean Surfaces Continentales et Atmosphere (TOSCA, France) program
• Centre Aval de Traitement des Donn´ees SMOS (CATDS)
• SWOT-AVAL project

Citation

@article{Guilhen2025Assessment,
  author = {Guilhen, Jérémy and Fabre, Clément and Parrens, Marie and Sauvage, Sabine and Mercier, Franck and Bitar, Ahmad Al and Martínez, Jean-Michel and Sánchez-Pérez, J.M.},
  title = {Assessment of surface water storage in the Amazon floodplains by hydrological modelling and earth observation data},
  journal = {Journal of Hydrology},
  year = {2025},
  doi = {10.1016/j.jhydrol.2025.134758},
  url = {https://doi.org/10.1016/j.jhydrol.2025.134758}
}