[Alumnos] *** Charla del Dr Damien Jougnot - Hoy a las 16hs en el salón Meridiano

[Ciencia y Técnica-FCAGLP]

Hoy a las 16hs en el salón Meridiano tendrá lugar la charla del  
profesor visitante Dr Damien Jougnot del Applied and Environmental  
Geophysics Group, Institute of Earth Sciences, University of Lausanne,  
Switzerland.

Título:Towards in situ water flux quantification in vadose zone using  
SP measurements, field application at the Voulund field site (Denmark)

Resumen:
Geophysics offers a variety of non-intrusive techniques to study  
near-surface processes of relevance for environmental sciences. One  
such technique is the self-potential (SP) method that is, among other  
contributors, sensitive to water fluxes. This contribution, the  
so-called streaming potential, results from the presence of an  
electrical double layer at the mineral-pore water interface. When  
water flows through the pore space, it gives rise to a streaming  
current and a resulting measurable electrical voltage.
Streaming current generation is well understood in water-saturated  
porous media, but its modeling under partial saturation is still an  
area of active research. To evaluate how SP data and state-of-the-art  
models can be used to characterize flow and transport phenomena in the  
vadose zone, we conducted field-based monitoring of vertical  
variations of the SP signal during 36 months. The investigations were  
carried out at the Voulund agricultural test site of the Danish  
hydrological observatory (HOBE).
The site is instrumented to monitor suction, water content and  
temperature down
to a depth of 3 m, together with meteorological variables and repeated
geophysical crosshole surveys. We installed 15 non-polarizable  
electrodes at 10
different depths within the vadose zone and placed the reference electrode
below the water table. Data were acquired every 5 minutes and the record
included various hydrologic events, such as natural infiltration, water table
rises, and a high salinity tracer infiltration. We developed a fully coupled
numerical scheme to simulate water fluxes and ionic transport in order  
to predict bulk electrical conductivity and the SP signal. The  
simulation results of the tracer test agreed rather well with the  
measured SP data. This model will now be used together with the 36  
months of data to carry out a detailed assessment of the predictive  
value of the SP method in vadose zone hydrology, with specific focus  
on in situ monitoring of water flux.

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