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Développement d'une modélisation du devenir de pesticides à l'échelle d'un versant au sein d'une plateforme hydrologique. Prise en compte de la macroporosité

Abstract : The general aim of the thesis is to improve representing and understanding of pesticide fate at the hillslope scale using a simplified spatial modeling approach. This has been done by integrating dominant processes at the hillslope scale in a hydrological framework, which would be "process-oriented", modular, scalable, and open source. Hydrological modeling framework CMF, developed at the Giessen University (Kraft, 2012) was chosen to implement this approach. The characterization of the hydrological response of this framework has been done in two steps: 1D simulations were first compared to those made via Hydrus1D ; 2D simulations were secondly compared with the results of Cathy model based on Sulis et al. (2010) benchmark to characterize the performance of the run-off, and with those of Hydrus2D (Simunek et al., 1999 & Simunek et al., 2001), on a hillslope similar to Morcille experimental hillslope, to characterize subsurface flow representation in CMF. The next step of this work was to develop a dual permeability model in CMF in order to model preferential flow that may occur within structured soil, which requires representing this process. The dual permeability approach (DP) was chosen to perform development of a new infiltration function in macropores surface. The DP model contains also two alternative functions to represent the matrixmacropores transfert: the first one is proportional to the difference of saturation degree of two soil compartments (Philip, 1968); the second function corresponds to a diffusing wave similar to the approach presented by van Genuchten (1993). Validation of the developed DP approach was done via a comparison with the dual permeability approach of Hydrus1D/2D, for the 4 soil-types. The results were similar in both models for the 1D case for the different tested soils. However, differences were observed in 2D. They may be explained by the different conceptualizations adopted by two models: CMF represents the preferential transfer on the vertical, while Hydrus2D represent fluxes in 2D. Finally, the solute transport in CMF was modeled using single porosity and dual permeability approaches, limited for now to the consideration of adsorption, neglecting degradation. The first tests showed that the dispersion process representation required to be improved. Overall, this thesis laid the foundation for adapting the CMF framework representing the pesticide fate within the watersheds, taking into account the landscape elements.
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  • HAL Id : tel-02602333, version 1
  • IRSTEA : PUB00046269

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K. Djabelkhir. Développement d'une modélisation du devenir de pesticides à l'échelle d'un versant au sein d'une plateforme hydrologique. Prise en compte de la macroporosité. Sciences de l'environnement. Doctorat, Sciences de la terre et univers, environnement, Université de Grenoble, 2015. Français. ⟨NNT : 2015GREAU012⟩. ⟨tel-02602333v1⟩

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