Basin-Scale Variational Hydrological-Hydraulic Model Calibration for River Discharge Estimation Using SWOT Altimetry

Basin-Scale Variational Hydrological-Hydraulic Model Calibration for River Discharge Estimation Using SWOT Altimetry | Authorea try { document.documentElement.classList.add('js'); } catch (e) { } var _gaq = _gaq || []; _gaq.push(['_setAccount', 'G-8VDV14Y67G']); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); Skip to main content Preprints Collections Wiley Open Research IET Open Research Ecological Society of Japan All Collections About About Authorea FAQs Contact Us Quick Search anywhere Search for preprint articles, keywords, etc. Search Search ADVANCED SEARCH SCROLL This is a preprint and has not been peer reviewed. Data may be preliminary. 21 January 2026 V1 Latest version Share on Basin-Scale Variational Hydrological-Hydraulic Model Calibration for River Discharge Estimation Using SWOT Altimetry Authors : Léo Pujol 0000-0002-8903-1270 [email protected] , Pierre-André Garambois 0000-0001-8350-6741 , Kevin Larnier 0000-0002-4350-6285 , and Jérôme Monnier 0000-0001-6227-7396 Authors Info & Affiliations https://doi.org/10.22541/au.176901862.25424328/v1 126 views 69 downloads Contents Abstract Supplementary Material Information & Authors Metrics & Citations View Options References Figures Tables Media Share Abstract Accurate river discharge prediction is critical for understanding hydrological responses. Yet, discharge estimation in ungauged basins remains a grand challenge due to sparse or unevenly distributed in situ discharge data - crucial constraints - and the fact that river surface geometry or velocity does not uniquely determine flow. Satellite altimetry, particularly from the SWOT mission, provides high-resolution measurements of river stage, slope, and width, but discharge inversion from these datasets alone is structurally indeterminate. We present a basin-scale variational data assimilation framework chaining a fully distributed, regionalizable hydrological model (SMASH) with a 1D hydraulic river network model (DassFlow1D). Hydrological closure is central: the hydrological model constrains upstream and lateral inflows, thereby regularizing the ill-posed hydraulic inverse problem and enabling coherent inference of high-dimensional spatio-temporal parameters-including bathymetry, friction, and hydrological parameters and states - via hydraulic-to-hydrology backpropagation. This effectively performs a double H\&H regionalization. The framework assimilates multi-source data, including SWOT observations and sparse discharge, and can be extended to additional datasets. Applied to the largely ungauged Maroni basin, the approach improves hydraulic and hydrological parameter estimation, enhances discharge simulations, and successfully reproduces altimetry-derived water-surface elevations. Results demonstrate that hydrological closure is key to unlocking information from river-surface observations, and that regionalized hydrology plays a pivotal role in controlling upstream inflows and river-network-scale hydraulic responses. This study establishes a foundation for basin-scale hydraulic-hydrological VDA applicable to other basins, and highlights the broader challenge of developing fully learnable, regionalizable H\&H solvers with complete adjoints for gradient-based optimization over large domains using multi-source observations. Supplementary Material File (1062073_0_merged_1768295695.pdf) Download 9.42 MB File (basin-scale variational hydrologicalxxxhydraulic model calibration for.pdf) Download 9.32 MB Information & Authors Information Version history V1 Version 1 21 January 2026 Copyright This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License Keywords 1d hydraulic network model gradient-based calibration hydrological-hydraulic modelling multi-satellite data assimilation parameter regionalization river discharge estimation Authors Affiliations Léo Pujol 0000-0002-8903-1270 [email protected] Laboratoire des Sciences de l'Ingenieur de l'Informatique et de l'Imagerie View all articles by this author Pierre-André Garambois 0000-0001-8350-6741 INRAE, Aix Marseille University, RECOVER View all articles by this author Kevin Larnier 0000-0002-4350-6285 HydroMatters View all articles by this author Jérôme Monnier 0000-0001-6227-7396 INSA Toulouse View all articles by this author Metrics & Citations Metrics Article Usage 126 views 69 downloads .FvxKWukQNSOunydq8rnd { width: 100px; } Citations Download citation Léo Pujol, Pierre-André Garambois, Kevin Larnier, et al. Basin-Scale Variational Hydrological-Hydraulic Model Calibration for River Discharge Estimation Using SWOT Altimetry. Authorea . 21 January 2026. DOI: https://doi.org/10.22541/au.176901862.25424328/v1 If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download. For more information or tips please see 'Downloading to a citation manager' in the Help menu . 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