Browsing by Author "Figueroa González, Ronny Javier"

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    Advances in the western Andean front aquifers characterization by gravimetric and electrical surveys (Central Chile - 32°50’S).
    (2020) Figueroa González, Ronny Javier; Yáñez Carrizo, Gonzalo Alejandro; Arancibia Hernández, Gloria Cecilia; Pontificia Universidad Católica de Chile. Escuela de Ingeniería
    En regiones áridas, las aguas subterráneas desempeñan un papel fundamental para el desarrollo de las actividades socioeconómicas y humanas. Las zonas montañosas proporcionan una gran parte del agua subterránea a través de diferentes mecanismos a las cuencas, donde las poblaciones se concentran mayoritariamente. Las zonas de falla condicionan la circulación del agua subterránea, debido a la modificación de la permeabilidad intrínseca de la roca fresca, en particular cuando se encuentra en la transición entre los frentes de montaña y las cuencas. Esta investigación se centra en la influencia de los límites y la geometría de las zonas de falla, en el flujo de agua subterránea de las áreas montañosas aledañas a la cuenca sedimentaria. Como caso de estudio, se estudió la Zona de Falla de Pocuro (PFZ), ubicada en la zona central de Chile (32.5S). Para llevar a cabo este objetivo, se usó una aproximación geofísica utilizando mediciones de gravedad y resistividad constreñida por datos geológicos e hidrogeológicos. Los resultados muestran variaciones significativas de la anomalía de la gravedad a lo largo de los perfiles: con (i) una anomalía nula en la parte alta de los cerros, debido a la fractura de las rocas, (ii) una anomalía negativa asimétrica al oeste del trazo de la falla, debido a un depocentro (alrededor de 150 - 200 m) de depósitos aluviales no consolidados en la cuenca, y (iii) variabilidad en los depósitos aluviales en la cuenca que sugiere una segmentación a lo largo de la zona PFZ. Las mediciones de resistividad eléctrica y las características de las aguas subterráneas (profundidad de la napa freática, conductividad eléctrica y ubicación de los manantiales) permiten definir tres posibles dominios hidrogeológicos: roca fracturada (de diferente intensidad), sedimentos y bandas subverticales de baja resistividad. Además, estas bandas subverticales, corroboradas con estudios geológicos, permiten un mapeo de fallas en profundidad. Finalmente, se propone un modelo conceptual para la Cuenca del Aconcagua en el borde de la PFZ, donde esta zona de falla es heterogénea y segmentada, por lo que la permeabilidad es variable a lo largo de la falla. El núcleo de falla es impermeable, debido a la presencia de salbanda rica en arcilla, mientras que las zonas de daño permiten el almacenamiento y el flujo del agua subterránea. Aunque este estudio se enfocó en la PFZ, la relación entre fallas y manantiales en otras partes de Chile sugiere que estas conclusiones pueden ser extrapoladas a otras zonas de fallas.
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    Deciphering groundwater flow-paths in fault-controlled semiarid mountain front zones (Central Chile)
    (2021) Figueroa González, Ronny Javier; Viguier, Benoît; Taucare, Matías; Yañéz Carrizo, Gonzalo Alejandro; Arancibia Hernández, Gloria Cecilia; Sanhueza Soto, Jorge Luis; Daniele, Linda
    The Mountain-Block Recharge (MBR), also referred to as the hidden recharge, consists of groundwater inflows from the mountain block into adjacent alluvial aquifers. This is a significant recharge process in arid environments, but frequently discarded since it is imperceptible from the ground surface. In fault-controlled Mountain Front Zones (MFZs), the hydrogeological limit between the mountain-block and adjacent alluvial basins is complex and, consequently, the groundwater flow-paths reflect that setting. To cope with the typical low density of boreholes in MFZs hindering a proper assessment of MBR, a combined geoelectrical-gravity approach was proposed to decipher groundwater flow-paths in fault-controlled MFZs. The study took place in the semiarid Western Andean Front separating the Central Depression from the Principal Cordillera at the Aconcagua Basin (Central Chile). Our results, corroborated by field observations and compared with worldwide literature, indicate that: (i) The limit between the two domains consists of N-S-oriented faults with clay-rich core (several tens of meters width low electrical-resistivity subvertical bands) that impede the diffuse MBR. The "hidden recharge' along the Western Andean Front occurs through (ii) focused MBR processes by (ii.a) open and discrete basement faults (mass defect and springs) oblique to the MFZ that cross-cut the N-S-oriented faults, and (ii.b) high-hydraulic transmissivity alluvial corridors in canyons. Alluvial corridors host narrow unconfined mountain aquifers, which are recharged by indirect infiltration along ephemeral streams and focused inflows from oblique basement faults. This study also revealed seepage from irrigation canals highlighting their key role M the recharge of alluvial aquifers in the Central Depression. The proposed combined geophysical approach successfully incorporated (hydro)geological features and geophysical forward/inverse modelling into a robust hydrogeological conceptual model to decipher groundwater flow-paths in fault-controlled MFZs, even in the absence of direct observation points. (C) 2021 Elsevier B.V. All rights reserved.
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    Unravelling geological controls on groundwater flow and surface water-groundwater interaction in mountain systems: A multi-disciplinary approach
    (ELSEVIER, 2023) Marti, Etienne Bernard Christian; Leray, Sarah Tiphaine Lucile; Villela, Daniela; Maringue Canales, José Ignacio; Yañez Morroni, Gonzalo José; Salazar, Esteban; Poblete, Fernando; Jiménez, Jose; Reyes, Gabriela; Poblete Farias, Guillermo Hernán; Huaman Sevilla, Zeidy Lisseth; Figueroa González, Ronny Javier; Araya Vargas, Jaime Andrés; Sanhueza, Jorge; Muñoz, Marjorie; Charrier, Reynaldo; Fernández, Gabriel
    Mountain water resources are considered to be the world's water towers. Still, despite their importance for downstream societies and ecosystems and their vulnerability to climate change, they remain poorly understood - It is the case in particular of mountain groundwater systems. Their complexity makes them difficult to conceptualize, while their remoteness makes them difficult to study, both observationally and instrumentally. Understanding mountain hydrogeological systems is mostly limited by the lack of characterization of the subsurface geologic framework and by the limited understanding of the role of geological structures on groundwater flow and on surface water-groundwater interaction. Removing methodological barriers is therefore a necessary step for improving the understanding of mountain hydrogeological systems. To tackle this problem, we develop a comprehensive multi-disciplinary approach to gain insights into the hydrogeological role of geological structures in ungauged mountain catchments. The methodology consists of several complementary methods: (1) geological mapping at multiple scales; (2) a geophysical study including on ground Electrical Resistivity Tomography (ERT) and, gravimetry transects, and a UAV-based magnetic survey; (3) hydraulic data, including a 9 km long transect of streamflow measurements in the recession period, the longterm Normalized Difference Vegetation Index (NDVI), and varied hydric markers (e.g., a thermal spring and a puddle). The methodology is tested in the Parque Nacional del Rio Clarillo, an ungauged catchment in the Andes Mountains (& AP;130 km2) that is illustrative of the complexity of mountain hydrosystems featuring fault zones, weathered zones, intrusive rocks, and volcano-sedimentary successions.An increase of approximately 50% in the streamflow is observed over a short distance of 1 km. Such a localized and significant increase in the baseflow is not related to any superficial supply and can only be explained by groundwater exfiltration. Based on the multiscale geological mapping and geophysical survey, a regional N-S fault and a secondary set of E-W local faults are identified in the vicinity of the resurgence area, which conjointly are likely to export groundwater from a neighbouring subcatchment up to the resurgence area. Downstream of the resurgence area, no significant change in the baseflow is observed, corresponding to the presence of an impermeable granitic pluton identified by the geological and geophysical mapping. Finally, a fractured zone in the Andean foothills is identified in the volcanic unit, which coincides with a perennial thermal spring, indicating upwelling flow and hydrogeological connectivity between the mountain block and the alluvial basin.The results strongly support the ability of the proposed methodology to identify geological structures that substantially impact the evolution of the baseflow through the catchment. The complementary multi-disciplinary methods are used innovatively to infer the link between geological and hydrogeological structures. The methodology does not aim to fully characterize the geological framework of the catchment but pragmatically focuses on hydrogeologically pertinent structures that may impact baseflow and consequently catchment management.