Connectivity of fractures and groundwater flows analyses into the Western Andean Front by means of a topological approach (Aconcagua Basin, Central Chile) | Analyses de la connectivité de fractures et des écoulements souterrains dans le Front Andin Occidental par une approche topologique (Bassin de l’Aconcagua, Chili Central) Análisis de conectividad de fracturas y circulación de agua subterránea en el Frente Occidental Andino mediante un enfoque topológico (Cuenca del Aconcagua, Chile Central) 用拓扑方法研究断裂和地下水向Andean前缘西部的流动之间的联系(智利中部Aconcagua盆地) Analisi della connettività delle fratture e flussi di acque sotterranee nel Fronte Andino Occidentale mediante un approccio topologico (Bacino del Aconcagua, Cile Centrale) Conectividade de fraturas e fluxos de águas subterrâneas na Frente Andina Ocidental por meio de uma abordagem topológica (Bacia do Aconcágua, Chile Central)
2020
Taucare, Matías | Viguier, Benoît | Daniele, Linda | Heuser, Gert | Arancibia, Gloria | Leonardi, Véronique
The misunderstanding of hydrogeological processes together with the oversimplification of aquifer conceptual models result in numerous inaccuracies in the management of groundwater resources. In Central Chile (32–36°S), hydrogeological studies have exclusively focused to alluvial aquifers in valleys (~15% of total area) and mountain-front zones remain considered as no-flux boundary conditions. By a topological approach and an analysis of fractures, the hydrogeological potential of the Western Andean Front along the N–S-oriented Pocuro Fault Zone (PFZ) in the Aconcagua Basin were determined. Perennial springs (23) show evidence of groundwater flows into the fractured Principal Cordillera. Topology allows for quantification of the density of connected fractures within the fault zone and its relationship with groundwater circulation. The study results highlight two areas where the density of fractures and connected nodes (Nc) is high (>2.4 km/km², 2.5 Nc/km²). Both areas are topologically related to the main springs of the PFZ: Termas de Jahuel (discharge ~14.0 m³/h at 22 °C) and Termas El Corazón (discharge ~7.2 m³/h at 20 °C). Outcrop-scale mapping reveals that groundwater outflows from NW–SE fractures, which is consistent with the preferential orientation of the fracture network (N30–60 W) within the PFZ. The results indicate that oblique basement faults are discrete high-permeability structures conducting groundwater across the Western Andean Front from the Principal Cordillera up to adjacent alluvial aquifers (focused recharge). Therefore, the simplistic hydrogeological view of the Western Andean Front (i.e. impervious limit) is partially erroneous.
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