Hydrodynamic, geochemical and isotopic characterization of the volcanic-sedimentary aquifer of Tumbaco-Cumbayá-Ilaló, Ecuador

Abstract : Volcanic and volcano-sedimentary aquifers often result from a complex geological history that induced a heterogeneous distribution of primary and reworked volcanic materials. The different stages, deposition, erosion, and tectonics affect the groundwater through its complex circulation flow. The Tumbaco – Cumbayá – Ilaló aquifer near Quito, Ecuador, exemplifies this context. It is an Andean confined volcano-sedimentary aquifer which has been used to supply water to the population in the valleys near Quito for three decades. In spite of abundant surface water resources, the increase of population and the industrial development leading to high contamin ation levels of rivers made it necessary to find new sources of potable water supply. This system is mainly composed of a sedimentary series including an aquitard (Cangahua), overhanging two volcanic sedimentary series (Chiche, Guayllabamba) presenting high hydraulic capacities, and a volcanic aquifer cone (Ilaló) virtually dividing the study zone in two. The Chiche-Guayllabamba aquifer is limited by natural barriers (river ravines or volcanoes) in all directions. A large hydrodynamical, geochemical and isotope study was carried out during four years, 2010 to 2013, complementing some old and partial data survey. It allowed to propose a conceptual model improving the understanding of the recharge process and flow circulation, seeking to aid the resource management. Results showed weak piezometric variations year round (A40 cm). Geochemical data highlighted a hydraulic continuity between the volcanic and sedimentary aquifers. Stable isotope data indicated the recharge area to be located on the volcanic slopes at local and regional scale. Tritium and radiocarbon gave apparent ages between 400 and more than 15000 years for the North Chiche formation, and between 11000 and 45000 years for Ilaló volcano. In the northern part, modern water was found in a spring which could be linked to a fractured zone allowing direct recharge from the surface by direct infiltration.
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https://hal.umontpellier.fr/hal-02125418
Contributeur : Pascale Roussel <>
Soumis le : vendredi 10 mai 2019 - 14:19:58
Dernière modification le : mardi 28 mai 2019 - 13:48:10

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  • HAL Id : hal-02125418, version 1

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Carla Manciati, J.D. Taupin, Christian Leduc, N. Patris. Hydrodynamic, geochemical and isotopic characterization of the volcanic-sedimentary aquifer of Tumbaco-Cumbayá-Ilaló, Ecuador. 43rd IAH International Congress “Groundwater and society : 60 years of IAH”, Sep 2016, Montpellier, France. ⟨hal-02125418⟩

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