Cerbelaud et al. (2026) Wide-swath altimetry maps bank shapes and storage changes in global rivers

Identification

• Journal: Nature
• Year: 2026
• Date: 2026-03-04
• Authors: A. Cerbelaud, J. Wade, C. H. David, M. Durand, R. P. M. Frasson, T. Pavelsky, H. Oubanas
• DOI: 10.1038/s41586-026-10218-y

Research Groups

• Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
• School of Earth Sciences, The Ohio State University, Columbus, OH, USA
• Department of Earth, Marine and Environmental Sciences, University of North Carolina, Chapel Hill, NC, USA
• G-EAU, Univ Montpellier, AgroParisTech, BRGM, CIRAD, INRAE, Institut Agro, IRD, Montpellier, France

Short Summary

This study leverages the first water year of the Surface Water and Ocean Topography (SWOT) mission to provide near-global observations of active river channel geometry and monthly water storage changes across 126,674 river reaches, revealing a global annual river storage variability of 313.1 ± 129.5 km³, which is approximately 28% lower than the lowest previously modelled estimates.

Objective

• To present near-global-scale observations of active river channel geometry and associated monthly changes in water storage at the reach scale, addressing the question: "What are the temporal and spatial scales of the hydrologic processes controlling surface-water storage and transport across the world’s continents?"

Study Configuration

• Spatial Scale: Near-global, covering 126,674 river reaches worldwide (73% of rivers wider than 30 meters) across major basins.
• Temporal Scale: First water year of the SWOT mission (October 2023 to September 2024), with monthly river storage anomaly calculations. Comparison with 30-year (1980-2009) model simulations.

Methodology and Data

• Models used:
  • Piecewise linear functions (three-part) fitted using an errors-in-variable approach to derive river hypsometric curves (width-water surface elevation relationships).
  • Mean Discharge Runoff and Storage (MeanDRS) model simulations (for comparison).
• Data sources:
  • Satellite: Surface Water and Ocean Topography (SWOT) mission's Level 2 KaRIn High Rate River Single Pass data product (RiverSP).
  • Hydrographic Network: SWOT River Database (SWORD) v16.
  • In situ validation: Global Runoff Data Centre (GRDC) for 61 representative river gauges.
  • Model comparison data: MeanDRS model estimates.
  • Translational dataset: MERIT–SWORD dataset for linking hydrographic networks.

Main Results

• Near-global characterization of active river corridor shapes (width-water surface elevation relationships) for 126,674 river reaches, revealing diverse morphologies (concave to convex, steep to gentle, stable to highly variable cross-sections).
• The observed global annual river storage variability (ΔRSA) is 313.1 ± 129.5 km³.
• This observed global ΔRSA is approximately 28% lower than the lowest previously modelled estimates (436.7 km³) for the same wide reaches.
• The Amazon River Basin exhibits the largest ΔRSA at 172.9 ± 16.4 km³. Other significant basins include the Ob (55.0 ± 8.1 km³), Indian subcontinent (52.0 ± 8. km³), Orinoco (46.5 ± 5.0 km³), and Congo (37.3 ± 4.8 km³).
• The Nile River Basin's observed ΔRSA of 8.5 ± 1.6 km³ is substantially lower than previous estimates (e.g., 93 km³ from MeanDRS low-volume scenario).
• Seasonal patterns of river storage variability generally align with latitudinal hydroclimatic gradients, with peak storage in the Amazon from March to May and in the Congo from October to December (north/central) or March to April (south).
• SWOT-derived RSA shows good consistency with in situ discharge records across most equatorial, tropical, and mid-latitude basins, but exhibits lower reliability in Arctic regions, southern South America, and the western USA due to ice cover and complex riverine environments.
• The 2023-2024 observation period coincided with exceptional drought conditions in the Amazon and generally below-average river conditions globally, likely contributing to the lower observed storage variability compared to climatological model averages.

Contributions

• Provides the first near-global observational record of active river channel geometry and monthly river water storage variability using wide-swath altimetry from the SWOT mission.
• Offers unprecedented fine-scale global measurements of river width and water surface elevation, addressing a key scientific objective of the SWOT mission.
• Challenges existing global hydrological model estimates of river storage variability by providing a significantly lower observational estimate, highlighting limitations in current surface-water science.
• Identifies opportunities to improve the fundamental representation of surface-water dynamics in global models, informing water resource management and disaster mitigation.
• Demonstrates the potential of SWOT observations to constrain and build more physically grounded, globally consistent models of river dynamics.

Funding

• Jet Propulsion Laboratory, California Institute of Technology (under contract with NASA)
• NASA Earth Science US Participating Investigator (NNH20ZDA001N-EUSPI)
• NASA Earth Science Applications: Water Resources (NNH21ZDA001N-WATER)
• NASA SWOT Science Team (NNH23ZDA001N-SWOTST) programmes
• NASA Grant 80NSSC25K7715
• CNES SWOT TOSCA programme

Citation

@article{Cerbelaud2026Wideswath,
  author = {Cerbelaud, A. and Wade, J. and David, C. H. and Durand, M. and Frasson, R. P. M. and Pavelsky, T. and Oubanas, H.},
  title = {Wide-swath altimetry maps bank shapes and storage changes in global rivers},
  journal = {Nature},
  year = {2026},
  doi = {10.1038/s41586-026-10218-y},
  url = {https://doi.org/10.1038/s41586-026-10218-y}
}