Browsing by Author "Gauvain, Alexandre"

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    Geomorphological Controls on Groundwater Transit Times: A Synthetic Analysis at the Hillslope Scale
    (2021) Gauvain, Alexandre; Leray Sarah, Tiphaine Lucile; Marcais, Jean; Roques, Clement; Vautier, Camille; Gresselin, Frederic; Aquilina, Luc; de Dreuzy, Jean Raynald
    We investigated how geomorphological structures shape Transit Time Distributions (TTDs) in shallow aquifers. Extensive three-dimensional simulations were performed to determine the TTDs for synthetic convergent, straight, and divergent hillslopes with a constant slope. The uniform recharge applied on top of the aquifer is transferred to the receiving stream through steady-state groundwater flows, return flows and saturation excess overland flows. Without seepage, TTDs evolve from uniform- to power law-like- distributions depending on the average distance of the groundwater volume to the river (barycenter). Remarkably, the coefficient of variation (ratio of the standard deviation to the mean) of the TTDs scales linearly with the barycenter in agreement with a theoretical prediction based on three analytical approximations derived for specific cases. With seepage, the TTD has three separate modes corresponding to rapid saturation excess overland flows, to the intermediate flow paths ending in seepage area and to the slower flow paths going all the way to a discharge in the river. The coefficient of variation additionally depends on the extent of the seepage area. For a natural hillslope in the crystalline basement of Normandy (France), the same synthetic analysis demonstrates that the coefficient of variation is not only determined by the extent of the seepage zone but also by its structure in relation to the local and global geomorphological organization. The results suggest the possibility to assess the variability of transit times by combining geomorphological analysis, surface soil saturation observations and environmental tracers.
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    HydroModPy: A Python toolbox for deploying catchment-scale shallow groundwater models 
    (2025) Gauvain, Alexandre; Abhervé, Ronan; Coche, Alexandre; Mesnil, Martin Le; Roques, Clément; Bouchez, Camille; Marçais, Jean; Leray Sarah,Tiphaine Lucile; Marti Etienne, Bernard Christian; Figueroa, Ronny; Bresciani, Etienne; Vautier, Camille; Boivin, Bastien; Sallou, June; Bourcier, Johan; Combemale, Benoit; Brunner, Philip; Longuevergne, Laurent; Aquilina, Luc; Dreuzy, Jean-Raynald de
    In response to the growing demand for groundwater flow models, we present HydroModPy, an open-source toolboxdesigned to automate their deployment at the catchment scale. Built on top of the MODFLOW-enabling FloPy library,HydroModPy combines the robust WhiteboxTools toolbox for geospatial analysis and the well-validated MODFLOW codefor groundwater modeling. This Python-based toolbox streamlines the construction, calibration, and analysis of unconfined aquifer models while adhering to FAIR (Findable, Accessible, Interoperable, and Reusable) principles. It enhances model reproducibility through editable Python code, supports multi-site deployment, and provides compatibility with alternative groundwater flow solvers. Furthermore, it integrates pre- and post-processing functionalities to simplify workflows. The toolbox enables catchment delineation and hydrological feature extraction from DEMs, followed by semi-automatic model construction and advanced visualization of hydraulic head and flow results. Users can choose from predefined aquifer structures and hydraulic properties such as exponential decay of hydraulic conductivity and porosity with depth or import complex 3Dgeological models. HydroModPy outputs can be exported in standard formats (e.g., raster, shapefile, netCDF), including water table elevation, water table depth, groundwater storage, groundwater-dependent hydrographic network and streamflow rates, and subsurface residence times. HydroModPy is tailored for the deployment in diverse geomorphological and hydrological settings, enabling the testing and exploration of aquifer models under varying recharge conditions. Its deployment capabilities are demonstrated in complex shallow basement and crystalline aquifers, where topography and geology primarily govern groundwater flow dynamics from hillslope to catchment scales. As an open-source toolbox, HydroModPy is designed for the community and actively encourages contributions from its users. It supports research in hydro(geo)logy and land and water management, while also providing valuable opportunities for teaching and education
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