Coupled hydrological-hydrodynamic and data assimilation of the Niger and Maroni using SWOT river products and other EO missions

International audienc

Integrated hydraulic-hydrological assimilation chain: towards multisource data fusion from river network to headwaters

International audienceIn a context of climate change and potential intensification of the hydrological cycle, improving representation of water fluxes within river basins is of paramount importance both for hydrological sciences and operational forecasts. New integrated approaches are required for exploring synergies between spatially distributed flow models and datasets, combining in situ observations with high-resolution hydro-meteorology and satellite data. To take advantage of this unprecedented observations of the critical zone, innovative approaches integrating hydraulic-hydrological modeling and multivariate assimilation methods are needed. They should enable ingesting spatially distributed forcings, physiographic descriptors hydrodynamic signatures from remotely-sensed and in situ observables, and tackle calibration problems in integrated hydraulic-hydrological models. Crucially, the pertinence of the information assimilation relies on model-data coherence: water surface observables are valuable to constrain hydraulic models of river reaches (Larnier et al. (2020) and references therein) and complex river network portions, forced by spatially distributed inflows (Pujol et al. (2020), Malou et al. (under redaction)). Since hydraulic modeling at the scale of a river basin can be computationally costly, a combination of effective 1D and 2D representations, complemented by hydrological modules, may be useful. Complex river-floodplain interaction zones may be modeled in 2D zooms, while 1D approaches can fit simpler reaches. This contribution presents the development of a complete hydraulichydrological toolchain based on the 2D hydraulic model and variational data assimilation platform DassFlow 2. A 1D effective modeling approach based on a 2D shallow water model is tested. Then, the implementation of hydrological modules within the DassFlow VDA framework is presented

INTEGRATED HYDRAULIC-HYDROLOGICAL ASSIMILATION CHAIN: TOWARDS MULTISOURCE DATA FUSION FROM RIVER NETWORK TO HEADWATERS

International audienceIn a context of climate change and potential intensification of the hydrological cycle, improving representation of water fluxes within river basins is of paramount importance both for hydrological sciences and operational forecasts. New integrated approaches are required for exploring synergies between spatially distributed flow models and datasets, combining in situ observations with high-resolution hydro-meteorology and satellite data. To take advantage of this unprecedented observations of the critical zone, innovative approaches integrating hydraulic-hydrological modeling and multivariate assimilation methods are needed. They should enable ingesting spatially distributed forcings, physiographic descriptors hydrodynamic signatures from remotely-sensed and in situ observables, and tackle calibration problems in integrated hydraulic-hydrological models. Crucially, the pertinence of the information assimilation relies on model-data coherence: water surface observables are valuable to constrain hydraulic models of river reaches (Larnier et al. (2020) and references therein) and complex river network portions, forced by spatially distributed inflows (Pujol et al. (2020), Malou et al. (under redaction)). Since hydraulic modeling at the scale of a river basin can be computationally costly, a combination of effective 1D and 2D representations, complemented by hydrological modules, may be useful. Complex river-floodplain interaction zones may be modeled in 2D zooms, while 1D approaches can fit simpler reaches. This contribution presents the development of a complete hydraulichydrological toolchain based on the 2D hydraulic model and variational data assimilation platform DassFlow 2. A 1D effective modeling approach based on a 2D shallow water model is tested. Then, the implementation of hydrological modules within the DassFlow VDA framework is presented

INTEGRATED HYDRAULIC-HYDROLOGICAL ASSIMILATION CHAIN: TOWARDS MULTISOURCE DATA FUSION FROM RIVER NETWORK TO HEADWATERS

International audienceIn a context of climate change and potential intensification of the hydrological cycle, improving representation of water fluxes within river basins is of paramount importance both for hydrological sciences and operational forecasts. New integrated approaches are required for exploring synergies between spatially distributed flow models and datasets, combining in situ observations with high-resolution hydro-meteorology and satellite data. To take advantage of this unprecedented observations of the critical zone, innovative approaches integrating hydraulic-hydrological modeling and multivariate assimilation methods are needed. They should enable ingesting spatially distributed forcings, physiographic descriptors hydrodynamic signatures from remotely-sensed and in situ observables, and tackle calibration problems in integrated hydraulic-hydrological models. Crucially, the pertinence of the information assimilation relies on model-data coherence: water surface observables are valuable to constrain hydraulic models of river reaches (Larnier et al. (2020) and references therein) and complex river network portions, forced by spatially distributed inflows (Pujol et al. (2020), Malou et al. (under redaction)). Since hydraulic modeling at the scale of a river basin can be computationally costly, a combination of effective 1D and 2D representations, complemented by hydrological modules, may be useful. Complex river-floodplain interaction zones may be modeled in 2D zooms, while 1D approaches can fit simpler reaches. This contribution presents the development of a complete hydraulichydrological toolchain based on the 2D hydraulic model and variational data assimilation platform DassFlow 2. A 1D effective modeling approach based on a 2D shallow water model is tested. Then, the implementation of hydrological modules within the DassFlow VDA framework is presented

Estimation of Multiple Inflows and Effective Channel by Assimilation of Multi-satellite Hydraulic Signatures: The Ungauged Anabranching Negro River

International audienceWith the upcoming SWOT satellite mission, which should provide spatially dense river surface elevation, width and slope observations globally, comes the opportunity to assimilate such data into hydrodynamic models, from the reach scale to the hydrographic network scale. Based on the HiVDI (Hierarchical Variational Discharge Inversion) modeling strategy (Larnier et al. [#Larnier2019]), this study tackles the forward and inverse modeling capabilities of distributed channel parameters and multiple inflows (in the 1D Saint-Venant model) from multisatellite observations of river surface. It is shown on synthetic cases that the estimation of both inflows and distributed channel parameters (bathymetry-friction) is achievable with a minimum spatial observability between inflows as long as their hydraulic signature is sampled. Next, a real case is studied: 871 km of the Negro river (Amazon basin) including complex multichannel reaches, 21 tributaries and backwater controls from major confluences. An effective modeling approach is proposed using (i) WS elevations from ENVISAT data and dense in situ GPS flow lines (Moreira [#DanielPhD]), (ii) average river top widths from optical imagery (Pekel et al. [#Pekel_Nature]), (iii) upstream and lateral flows from the MGB large-scale hydrological model (Paiva et al. [#paiva2013]). The calibrated effective hydraulic model closely fits satellite altimetry observations and presents real like spatial variabilities; flood wave propagation and water surface observation frequential features are analyzed with identifiability maps following Brisset et al. [#Brisset_2018]. Synthetic SWOT observations are generated from the simulated flowlines and allow to infer model parameters (436 effective bathymetry points, 17 friction patches and 22 upstream and lateral hydrographs) given hydraulically coherent prior parameter values. Inferences of channel parameters carried out on this fine hydraulic model applied at a large scale give satisfying results using noisy SWOT-like data at reach scale. Inferences of spatially distributed temporal parameters (lateral inflows) give satisfying results as well, with even relatively small scale hydrograph variations being inferred accurately on this long reach. This study brings insights in: (i) the hydraulic visibility of multiple inflows hydrographs signature at large scale with SWOT; (ii) the simultaneous identifiability of spatially distributed channel parameters and inflows by assimilation of satellite altimetry data; (iii) the need for prior information; (iv) the need to further tailor and scale network hydrodynamic models and assimilation methods to improve the fusion of multisource information and potential information feedback to hydrological modules in integrated chains