Browsing by Author "Marti, Etienne"

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    Assessing Structural Geological Controls on Groundwater Processes in Mountain Settings: Insights From Three‐Dimensional Numerical Modeling
    (2025) Marti, Etienne; Leray, Sarah; Roques, Clément; Yáñez Carrizo, Gonzalo Alejandro; Poblete, Fernando; Abhervé, Ronan; Tapia, Felipe; Villela, Daniela; Butikofer, Pol
    Mountains play a critical role in the hydrological cycle by transferring heavy precipitation to lowland aquifers. However, their complexity and remoteness limit our understanding of groundwater flow, particularly the influence of faults. To fill the gap, semi-idealized 3D numerical models calibrated using the mountain river network and the lowland piezometric gradient were developed. The impact of faults on groundwater flow was explored by varying their hydraulic conductivity, position, orientation, and length. The metrics evaluated were flow partitioning, seepage area, flow path lengths, and residence times. It was found that the hydraulic conductivity contrast between a fault and the pervasive rock controls recharge partitioning as much as the overall transmissivity of the pervasive rock. Regional conductive faults parallel to the orogen promote mountain-block recharge over surface flow, as significantly as thick systems do, and vice versa. Local-scale faults can exert as much influence as regional faults when crossing the catchment outlet, highlighting the importance of local heterogeneity in regional flow dynamics. Intercatchment flow is primarily governed by lithology and topography and is modulated by the fault position relative to major topographic features. Faults influence seepage areas within a multi-kilometer distance in characteristic patterns useful for segregating their effective role. By lowering the water table, conductive faults systematically reduce the seepage areas. Meanwhile, barriers decrease seepage areas downstream of their trace and increase them upstream, without affecting the extent of seepage. Finally, the distributions of flow path lengths and residence times are uncorrelated, highlighting the importance of numerical modeling for groundwater dating.
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    Recession discharge from compartmentalized bedrock hillslopes: hydrogeological processes and solutions for model calibration
    (2024) Clement Roques; Ronan Abhervé; Marti, Etienne; Nicolas Cornette; Jean-Raynald de Dreuzy; David Rupp; Alexandre Boisson; Sarah Leray; Philip Brunner; John Selker
    Due to the difficulties of gathering relevant data of groundwater systems and the lack of fundamental physically-based understanding on the processes involved, the representation of groundwater flow heterogeneity in catchment- to regional-scale hydrological models is often overlooked. We often limit the representation of groundwater with simplified homogeneous and shallow aquifers where effective hydraulic properties are derived from global-scale database. This raises questions regarding the validity of such models to quantify the potential impacts of climate change, where subsurface heterogeneity is expected to play a major role in their short- to long- term regulation.We will present the results of a numerical modelling experiment designed to explore the role of the vertical compartmentalization of hillslopes on groundwater flow and recession discharge. We found that, when hydraulic properties are vertically compartmentalized, streamflow recession behaviour may strongly deviate from what is predicted by groundwater theory that considers the drainage of shallow reservoirs with homogeneous properties. We further identified the hillslope configurations for which the homogeneous theory derived from the Boussinesq solution approximately holds and, conversely, for those for which it does not. By comparing the modelled streamflow recession discharge and the groundwater table dynamics, we identify the critical hydrogeological conditions responsible for the emergence of strong deviations. We further present new solutions to better represent subsurface heterogeneity in catchment-scale models and calibrate hydraulic parameters that properly capture the groundwater and streamflow dynamics.
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    Topographical, climatic, and geological controls of groundwater flow in mountainous systems - impact on mountain block recharge and groundwater-surface water interaction
    (2024) Marti, Etienne; Leray, Sarah; Yáñez, Gonzalo; Pontificia Universidad Católica de Chile. Escuela de Ingeniería
    Mountains, often referred to as the world's water towers, play a vital role in global water distribution. They receive significant precipitations and redistribute these waters to lower regions, thereby sustaining a major portion of our planet's water needs. Moreover, in the face of climate change and increasing human water consumption, lowland aquifers are experiencing unprecedented depletion. Thus, there is a crucial need to characterize all recharge sources arriving at the lowland aquifers, including both surface and groundwater contribution. Nevertheless, the complexity of mountain systems and their remoteness impede full comprehension of their functioning. In this context, this thesis aims to deepen our understanding of mountainous groundwater systems and their crucial connection to lowland basins. The methodology is two-fold, using parsimonious numerical models to grasp the broader hydrogeological dynamics, and secondly, implementing an innovative, interdisciplinary field study to examine local peculiarities. This study reveals that the topography highly influences aquifer desaturation patterns and hence groundwater-surface water interactions, further determining biogeochemical and ecological processes and impacting groundwater dependent systems. The slope contrast between flat and steep areas exerts the principal control, while landscape shape exerts a secondary control. Regarding geological heterogeneities, at the local scale, using a novel methodology, geological structures were identified and satisfactorily linked them to an increase in streamflow. Finally, in studying regional geological heterogeneities, the study unveils the role of such structures and their hydrodynamic properties on groundwater flows pattern and interbasins exchanges. The studied catchment consistently exchanges between 0 and 20% with surrounding catchments. while characterizing the contribution of mountain systems to lowland areas. This research by questioning existing groundwater paradigms and their applicability on mountain systems thoroughly study the groundwater flow controls improving paradigms definition in mountain systems. By establishing a robust framework for future research, it underscores the need for multidisciplinary approaches to develop a comprehensive understanding of mountainous regions as vital contributors to global water resources.