Browsing by Author "Leray, Sarah"

Now showing 1 - 6 of 6
  • No Thumbnail Available
    Item
    Assessing permafrost structures in headwater aquifers: an example from the Ojos del Salado massif, Andes mountains
    (2024) Ruiz Pereira, Sebastián; Leray, Sarah; Marti, Etienne; Beriain, Eneko; Suárez, Francisco; Yáñez Carrizo Gonzalo Alejandro; Nagy, Balázs
  • No Thumbnail Available
    Item
    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.
  • Thumbnail Image
    Item
  • Thumbnail Image
    Item
    Potential impacts of climate change on an aquifer in the arid Altiplano, northern Chile: The case of the protected wetlands of the Salar del Huasco basin
    (2022) Blin, Nicole; Hausner, Mark; Leray, Sarah; Lowry, Christopher; Suarez Poch, Francisco; CEDEUS (Chile)
  • Thumbnail Image
    Item
    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.
  • Thumbnail Image
    Item
    Using a robust decision making (RDM) approach to explore current and future vulnerabilities of a semi-arid coastal basin: a case study of the Quilimarí basin in Chile
    (2025) Poblete López, David Nicolás; Vicuña Díaz, Sebastián; Aedo, Sebastián; Molina-Pérez, Edmundo; Cortés, Hermilo; Melo Contreras, Óscar; Ocampo-Melgar, Anahí; Tesen Arambulo, Kiara Aimee; Suárez Poch, Francisco Ignacio; Herane Espinosa, Juan Pablo; Meza, Francisco Javier; Duarte Becerra, Katherine Mariela; González Santander, Diego Nicolás; Leray, Sarah; Williams, Megan Elizabeth; Gaxiola, Aurora; Alfaro, Gabriela; Morales Moraga, David Alejandro
    Climate change, land use alterations, human activities, and regulatory frameworks all contribute to deep uncertainties that define water security in hydrological basins. This is particularly significant in drylands where water scarcity limits agricultural productivity. Robust Decision Making (RDM) is an effective approach for identifying strategies that perform well under uncertainty across a wide range of possible futures. One of RDM’s key strengths is its ability to guide decisions without relying on precise future predictions, emphasizing robustness rather than optimality. This study focuses on the Quilimarí River basin, located in the semi-arid coastal region of Chile, where groundwater is the primary water source. Small coastal communities rely on shallow boreholes, which have become brackish due to saline intrusion. We present the initial stages of implementing an RDM process with key local decisionmakers to explore the expected impacts of socio-hydrological stressors and uncertainties on the main water-dependent objectives. Different levels and approaches of participation during the 2 years of RDM process enabled the identification of critical concerns raised by local stakeholders and government agencies, the uncertainties likely to affect these issues, and potential actions for improving outcomes. To explore current and future vulnerabilities we used a WEAP-MODFLOW water resources model that integrates data on extraction wells, irrigation schemes, agricultural production, potable water supply, and associated costs, including saline intrusion processes. The model simulates trade-offs between different objectives, such as groundwater extraction for agriculture and job creation versus potable water for rural communities. The vulnerability exploration scenarios suggest a complex future, with up to a 40% reduction in precipitation and increased water demand from household and tourism use. To cope with the impacts associated with these global change scenarios a series of adaptation options were tested. Overall, desalination emerged as a favorable option for local human consumption demands, although tested only under basin-level metrics. This study illustrates valuable insights on how the water management strategies under uncertainty can benefit from local engagement towards testing robust decisions in arid and semi-arid coastal basis around the world.