Hydrological connectivity of alluvial Andean valleys: a groundwater/surface-water interaction case study in Ecuador

Guzman, Pablo; Anibas, Christian; Batelaan, Okke; Huysmans, Marijke; Wyseure, Guido

Hydrological connectivity of alluvial Andean valleys: a groundwater/surface-water interaction case study in Ecuador | Connectivité hydrologique des vallées alluviales andéennes: cas d’étude des interactions eau souterraine/eau de surface en Equateur Conectividad hidrológica de los valles aluviales andinos: caso de estudio de interacción del agua subterránea/agua superficial en Ecuador 安第斯山脉冲积河谷水文连通性:厄瓜多尔地下水/地表水相互作用研究实例 Conectividade hidrológica dos vales andinos aluviais: o estudo de caso da interação das águas subterrâneas/águas superficiais no Equador

2016

Guzman, Pablo | Anibas, Christian | Batelaan, Okke | Huysmans, Marijke | Wyseure, Guido

The Andean region is characterized by important intramontane alluvial and glacial valleys; a typical example is the Tarqui alluvial plain, Ecuador. Such valley plains are densely populated and/or very attractive for urban and infrastructural development. Their aquifers offer opportunities for the required water resources. Groundwater/surface-water (GW–SW) interaction generally entails recharge to or discharge from the aquifer, dependent on the hydraulic connection between surface water and groundwater. Since GW–SW interaction in Andean catchments has hardly been addressed, the objectives of this study are to investigate GW–SW interaction in the Tarqui alluvial plain and to understand the role of the morphology of the alluvial valley in the hydrological response and in the hydrological connection between hillslopes and the aquifers in the valley floor. This study is based on extensive field measurements, groundwater-flow modelling and the application of temperature as a groundwater tracer. Results show that the morphological conditions of a valley influence GW–SW interaction. Gaining and losing river sections are observed in narrow and wide alluvial valley sections, respectively. Modelling shows a strong hydrological connectivity between the hillslopes and the alluvial valley; up to 92 % of recharge of the alluvial deposits originates from lateral flow from the hillslopes. The alluvial plain forms a buffer or transition zone for the river as it sustains a gradual flow from the hills to the river. Future land-use planning and development should include concepts discussed in this study, such as hydrological connectivity, in order to better evaluate impact assessments on water resources and aquatic ecosystems.

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