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Modélisation des échanges nappe-rivière à l'échelle intermédiaire : conceptualisation, calibration, simulation

Abstract : The interactions between surface-water and groundwater are complex and play a significant part in the functioning of the hydrosystems, both in quantitative (low flow support, flood events) and qualitative terms (transport of pollutants from agricultural or industrial origin). These issues are addressed through the characterization and the modeling of stream-aquifer exchanges at median scale [1-10 km], through the case study of the well field of Thil-Gamarde which supplies the city of Bordeaux in drinking water. The well field is crossed by a stream, the Jalle de Saint-Médard, which is a historical vector of pollution. A first phase is constituted of a theoretical part, aiming to improve the ways of including streams in hydrogeological models from median to regional scale, through a head-dependent flux boundary condition (Cauchy-type). A tool has been developed which allows their integration from prior information on hydrodynamics and geometrics parameters of stream and aquifer, often neglected so far. The study of Thil-Gamarde’s well field starts with the setting-up of the conceptual model of flow and transport in the aquifer. The considered multidisciplinary approach is constituted of hydrogeological field investigations completed with hydro-chemical and geophysical investigations, which allow the acquisition of prior information on system functioning. A 2D horizontal flow and transport model, in transient condition has then been developed. The model calibration has been performed with the Gauss-Lavenberg Marquardt algorithm implemented in the PEST++ suit code. A Tikhonov-type regularization on prior information of each parameter is carried out so as to regulate the calibration. A mathematical regularization (SVD) has also been lead. The transport calibration step through the resolution of the advective-dispersive equation is too time consuming. To overcome this issue, a fast surrogate model of advective transport with particle tracking has been developed. As the outcome of this calibration step, parametric and predictive uncertainty of the model has been completed by linear analysis and the method of the Null-Space Monte Carlo. Finally, some prospective management scenarios have been evaluated, so as to answer to the main stress of reducing stream water in pumping wells.
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https://hal.archives-ouvertes.fr/tel-01567824
Contributor : Yohann Cousquer <>
Submitted on : Monday, July 24, 2017 - 3:26:54 PM
Last modification on : Tuesday, July 9, 2019 - 10:12:00 AM

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  • HAL Id : tel-01567824, version 1

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Yohann Cousquer. Modélisation des échanges nappe-rivière à l'échelle intermédiaire : conceptualisation, calibration, simulation. Hydrologie. Université Bordeaux Montaigne, 2017. Français. ⟨tel-01567824⟩

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