Apports croisés de la modélisation géostatistique et déterministe : exemple des nitrates et de l'oxygène dissous dans un réseau hydrographique

Abstract : The river water quality is characterized either from measurement networks with a few sites by edge or thanks to physics-based models that simulate physical processes approximately. This thesis explore the solutions that geostatistics offer to improve the estimation of concentrations along a river network based on measurements, and then to combine these measurements with the physics-based simulation. A variographic model valid on a tree was developed by C. Bernard-Michel (2006), but its inference was made impossible by the too small account of measurement sites. To remedy this lack of data, the idea consists in considering the physics-based model ProSe (Even et al, 1998, 2004, Flipo et al, 2004) as a replica of reality. For nitrates and dissolved oxygen, the ProSe model outputs are first compared to different measurement sets, revealing discordances. Upstream boundary conditions combining these different kinds of measurement are reconstituted by co-kriging, what improve the agreement between ProSe outputs and measurements. Besides, the joint modelling of variograms of Prose outputs and measurements turns out to be an efficient tool for diagnosing the physics-based model imperfections. Admitted as a replica of reality, the ProSe simulation is then used to test the hypotheses of the geostatistical modelling and to perform its inference. Different geostatistical models for the estimation of concentrations based on measurements are then compared. Finally a geostatistical estimation combining the ProSe simulation with measurements is carried out, with promising results.
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Edwige Lefebvre Polus. Apports croisés de la modélisation géostatistique et déterministe : exemple des nitrates et de l'oxygène dissous dans un réseau hydrographique. Hydrologie. École Nationale Supérieure des Mines de Paris, 2010. Français. ⟨NNT : 2010ENMP0048⟩. ⟨pastel-00563806⟩

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