Browsing by Author "Calispa Aguilar, Marlon Fabricio"

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Delineation of water flow paths in a tropical andean headwater catchment with deep soils and permeable bedrock
(2022) Páez Bimos, Carlos Sebastián; Calispa Aguilar, Marlon Fabricio; Vanacker, Veerle; Zapata Ríos, Xavier; Muñoz Martínez, Teresa del Rocío; Crespo Sánchez, Patricio Javier; Lahuatte Imbaquingo, Braulio Cesar; Mosquera, Giovanny
Traditional hydrometric data combined with environmental tracers such as water stable isotopes contributes to improve the understanding of catchment hydrology. Nevertheless, the application of isotopic tracers in headwater catchments of the tropical Andes with deep soils and permeable parent material influenced by recent volcanism remains limited. In this study, the stable isotopic composition of precipitation, soil water, wetlands, and streamflow was studied to provide insights into the hydrology of a small tropical Andean catchment with deep and permeable volcanic soils, ash layers, and fractured bedrock resulting from Holocene volcanic activity. Although local precipitation forms under isotopic equilibrium conditions, the stable isotopic composition of precipitation is influenced by atmospheric moisture recycling processes. The spatial and temporal variability of isotopic signals and the analysis of inverse transit time proxies (ITTPs) of surface (streamflow) and subsurface (soil and wetlands) waters indicate that vertical flow paths through the deep volcanic ash soils are dominant across the catchment. The strongly damped isotopic composition of these waters points to high soil and wetlands water storage, increasing the transit time or age of stream water in the hydrological system. These findings indicate that water mobilizing through subsurface flow paths–that is, volcanic soils, ash layers, and cracks in the fractured bedrock resulting from Holocene volcanism–is the main contributor to streamflow generation. Comparison with previously published work from Andean catchments and other volcanic areas shows the diversity of hydrological conditions that can be found as a result of pedological and lithological differences shaped by volcanic activity. Therefore, site-specific strategies may be needed to improve water resources management
Vegetation effects on soil pore structure and hydraulic properties in volcanic ash soils of the high Andes
(2022) Vanacker, Veerle
Soil hydraulic properties control the provision of hydrological services. Vegetationand topography influence these properties by altering soil structure and porosity. Theunderlying mechanisms are not yet fully understood for the high Andean region. Inthis study, we examined how vegetation and topographic attributes are related to soilhydraulic properties and soil pore structure in young volcanic ash soils, and furthercorrelated them to soil texture, organic carbon, and root characteristics to explainthese relationships. In a 0.7 km2study site located in the Andean páramo of northernEcuador, we measured soil water retention, saturated hydraulic conductivity, bulkdensity (BD), and pore size distribution parameters on eight soil profiles with con-trasting vegetation types (cushion-forming plants vs. tussock grasses) and topo-graphic positions (summit vs. hillslope). We observed significant differences in soilhydraulic properties and soil pore structure in the uppermost horizons by vegetationtype, whereas topography had a minor effect. In the A horizons, we found higherwater retention at saturation and field capacity (10%–14%), higher total availablewater (8%–15%), and higher saturated hydraulic conductivity (4–12 times) undercushion-forming plants compared to tussock grasses. The elevated values under cush-ion plants were attributed to the presence of larger pores, lower soil BD, and highersoil organic carbon content as a result of coarser root systems. Total available waterwas generally high (0.34–0.40 cm3cm 3), and locally not associated with any soilproperty. The higher water retention in soils under cushion vegetation can enhancesoil water storage for plants and the regulation of water flows during prolonged rainfall events. The saturated hydraulic conductivity of the surface horizons is highcompared to rainfall intensities resulting in high infiltration capacity; whilst its declinewith depth reveals the potential for generation of subsurface stormflow, especiallybelow cushion-forming plants. Our findings highlight that soil hydraulic properties dif-fer among vegetation types, and show the significance of vegetation types for soilhydrology