Analyse des effets d'échelle, d'organisation spatiale et de structuration géomorphologique pour la modélisation des débits et de flux hydrochimiques en bassins non jaugés

Abstract : The knowledge of hydrological and hydrochemical dynamics is essential for policy makers to develop appropriate policies of remediation, but this goal is hard to achieve in « ungauged catchments ». Through the inversion of a geomorphology-based hydrological modelling, the net rainfall entering the stream network is assessed from a gauged catchment. This net rainfall is scale independant and can be convoluted in another (ungauged) catchment. This method is applied for the first time in a pluvio-nival context on 21 catchments from Québec. Success of the simulation depends of the hydrological similarity between gauged and ungauged catchments, which is defined as the ensemble of caracteristics insuring a close functionning. We test how riverwater chemical composition reveals this similarity through a synoptic spectral analysis developped on western France. Groups of catchments are identified by their spatial homogeneity/heterogeneoty of the hydrochemical facies, and the area at which hydrochemical stabilisation occurs. This result suggest that riverwater chemical composition is informative of a hydrological similarity. This hypothesis is successfully tested on six mesoscale catchments, by transposing hydrographs and concentration discharge relatioships (CQ), best transpositions are associated to similar catchments. Finally, the coupling of hydrological simulation to CQ curves allowed the prediction of hydrochemical fluxes in ungauged catchments with a 15 minutes timestep.
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https://tel.archives-ouvertes.fr/tel-02268819
Contributor : Abes Star <>
Submitted on : Wednesday, August 21, 2019 - 4:19:29 PM
Last modification on : Thursday, August 22, 2019 - 1:10:42 AM

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Stéphane Ecrepont. Analyse des effets d'échelle, d'organisation spatiale et de structuration géomorphologique pour la modélisation des débits et de flux hydrochimiques en bassins non jaugés. Sciences de la Terre. Université Rennes 1, 2019. Français. ⟨NNT : 2019REN1B007⟩. ⟨tel-02268819⟩

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