Topographical, climatic, and geological controls of groundwater flow in mountainous systems - impact on mountain block recharge and groundwater-surface water interaction
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Date
2024
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Abstract
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.
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Tesis (Doctor in Engineering Sciences)--Pontificia Universidad Católica de Chile, 2024.