Pesticide use on agricultural surfaces leads to a broad surface and subsurface water contamination in France. Awaiting a deep agricultural practices evolution and a sustained fall of the pesticide use, it is of interest to limit transfers form agricultural fields to rivers. In order to constrain those transfers, a deepen knowledge of processes at stake and their potential interactions is necessary, as well as taking full advantages of fields observations.The aim of this PhD is the reactive transfer processes integration in the Hydrological physically-based model CATHY (CATchment HYdrology) which simulates surface-subsurface coupled water flow and advectiv solute transport in three dimensions and in variably saturated situations. Linear adsorption and first order decay are implemented in subsurface. A mixing modules is added, and evens the concentration between surface runoff and subsurface first layer. This module simulates the solute mobilisation from soil to surface runoff. The water flow surface-subsurface coupling procedure is very accurate in CATHY, and the transport coupling procedure is improve in order to respect the mass conservation.The model is first evaluated on subsurface transfer laboratory experimentation data at a small scale (2 m long, o.5 m wide, 1 m deep). Results are compared to mass flux evolution in time and a Morris sensitivity analysis is conducted. The model is able to acceptably reproduce observation, and properly after a slight calibration. Horizontal and vertical saturated conductivities, porosity and the n parameter of retention curve significantly influence hydrodynamics and solute transport. As a second step, the model is evaluated on data from a field wine hillslope on an intense rain event, therefore in a context with a lot of surface-subsurface interactions. A global sensitivity analysis is conducted and highlights same parameters as the Morris method. Interactions between parameters highly influence the variability of hydrodynamic and solute transfer outputs. Mass conservation is accurate despite the complexity of the context.The resulting model meets the objectives, its evaluation is strong even if its theoretically only valid in the precise context in which the evaluations where conducted. The model is robust and able to reproduce observed data. Some complementary processes are still missing in the model to properly represent transfer ways at the hillslope scale, such as subsurface preferential transfers and surface sedimentary transport.

Publications

• Gatel, L., Lauvernet, C., Carluer, N., & Paniconi, C. (2016). Effect of surface and subsurface heterogeneity on the hydrological response of a grassed buffer zone. Journal of Hydrology, 542, 637-647.
• Gatel, L. (2018). Construction et évaluation d'un modèle de transport de contaminants réactif couplé surface-subsurface à l'échelle du versant. Thèse de doctorat, Université Grenoble Alpes.
• Gatel, L., Lauvernet, C., Carluer, N., Weill, S., Tournebize, J., & Paniconi, C. (2019). Global evaluation and sensitivity analysis of a physically based flow and reactive transport model on a laboratory experiment. Environmental Modelling & Software, 113, 73-83.
• Gatel, L., C. Lauvernet, N. Carluer, S. Weill, and C. Paniconi. 2019. Sobol Global Sensitivity Analysis of a Coupled Surface/Subsurface Water Flow and Reactive Solute Transfer Model on a Real Hillslope. Water 12. MDPI AG: 121. doi:10.3390/w12010121.

International Conferences

• Gatel L., Lauvernet C., Carluer N., Leblois E., Paniconi C., Influence of soil spatial variability on surface and subsurface flow at a vegetative buffer strip scale; EGU - European Geoscience Union - Wein, 2015; Présentation orale
• Gatel L., Lauvernet C., Carluer N., Tournebize J., Paniconi C., Implementation and testing of reactive transport processes for a coupled (groundwater/surface water) physically based model; CMWR - Computational Methods in Water Resources - Toronto, 2016; Présentation orale
• Gatel L., Lauvernet C., Carluer N., Paniconi C. Application of a reactive transport processes module for a coupled (groundwater/surface water) physically based model on a vineyard hillslope (Beaujolais, France); Pesticide behaviour in soil, water & air – York, 2017, Lauréate du prix du meilleur poster.
• Gatel L., Lauvernet C., Carluer N., Paniconi C., Implementing and evaluating a surface-subsurface flow and reactive solute transport model at the hillslope scale; CMWR - Computational Methods in Water Resources – Saint-malo, 2018; Présentation orale

Cite the thesis

Laura Gatel. Construction et évaluation d'un modèle de transport de contaminants réactif couplé surface-subsurface à l'échelle du versant. Géochimie. Université Grenoble Alpes; Institut national de la recherche scientifique (Québec, province), 2018. Français. ⟨NNT : 2018GREAU001⟩. ⟨tel-02607327v2⟩

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