Browsing by Author "Guzman Cardenas, Pablo Ismael"

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Comparative analysis of baseflow characteristics of two Andean catchments, Ecuador
(JOHN WILEY AND SONS LTD, 2015-07-01) Guzman Cardenas, Pablo Ismael
Baseflow in the Andes is commonly considered to be related with the release of water stored in páramos. Páramo is the predominant ecosystem above 3500m a.s.l. and is characterized by a rainy and cold climate with low evapotranspiration. However, this baseflow concept is based on hydrological process studies in small Andean catchments of a few square kilometre with a homogeneous land cover. Middle-sized Andean catchments, like the subcatchments of Tarqui and Yanuncay, Ecuador, are rarely homogeneous or uniformly covered by páramo. The objectives of this study are therefore to investigate baseflow characteristics in heterogeneous Andean catchments and to identify relationships between baseflow processes and physical characteristics such as storage and recharge. Hereby, the contribution to baseflow of páramo and other sources such as alluvial aquifers is quantified. This study uses nonlinear recession analysis, physically based filters and digital filters for comparison of baseflow of neighbouring but distinct subcatchments. The Yanuncay subcatchment shows a clearly different storage capacity and recession. The storage capacity of Yanuncay is 50% higher than for Tarqui because of its higher coverage of páramo. On the other hand, considerable storage capacity has also been found in the Tarqui subcatchment, which has a limited páramo area but a significant alluvial aquifer. It is shown that improved understanding of the specific baseflow characteristics such as storage and recharge and its relationships to the heterogeneity of the land cover in Andean catchments will lead to a better assessment of the water resources and give new insights for effective management actions.
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] [Conectividade hidrológica dos vales andinos aluviais: o estudo de caso da interação das águas subterrâneas/águas superficiais no Equador] [Conectividad hidrológica de los valles aluviales andinos: caso de estudio de interacción del agua subterránea/agua superficial en Ecuador]
(SPRINGER VERLAG, 2016-01-01) Guzman Cardenas, Pablo Ismael
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.
Rainfall-runoff modelling using a spatially distributed electrical circuit analogue
(SPRINGER NETHERLANDS, 2016-06-01) Guzman Cardenas, Pablo Ismael
The assessment and prevention of floods require appropriate forecasting and knowledge of the related hydrological processes. Due to the similar form of the governing equations, flood hydrograph shows a clear analytical and mathematical analogy with electrical circuits. In this paper, a spatially distributed hydrological model is developed which is analogue to a network of electrical resistance–capacitance with five circuits for describing the hydrological processes leading to floods. The spatially distributed hydrological model simulates rainfall, potential evapotranspiration, canopy interception, surface storage and soil storage. The parameters for analogical modelling were derived from translation of the physical catchment characteristics. A two-parameter Weibull equation aggregates the response functions of each pixel and calculates the hydrograph of the catchment. We applied the model to the ‘Open-Book’ or ‘tilted V-catchment’ theoretical benchmark problem, as well as to four hourly flood events and simulation of daily discharges. For the last two cases, data were used from the mountainous catchment of upper Tarqui in the Andes of Ecuador. Comparison of single versus multiple circuit designs for the benchmark problem indicates that the multiple circuit analogy provides a result similar to other hydrological models. The results further illustrate the usefulness of the methodology for flood modelling and how it can simplify the simulation for ungauged basins of temporal and spatial variations of influencing hydrological processes.