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| Titel |
Assessment of the water exchange between soil and groundwater in an Alpine valley |
| VerfasserIn |
Amro Negm, Marco Falocchi, Stefano Barontini, Roberto Ranzi, Baldassare Bacchi |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250083478
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| Zusammenfassung |
| The soil–water balance in temperate climates can be sensitively characterised by the water
exchange between soil and groundwater. Particularly in mountain environments, where the
soil and the water table depth are shallow, both percolation and water rise from the water
table can happen, but these latter extimate is still a major challenge for hydrological
applications.
Aiming at contributing to better characterise the soil–water balance and the water
exchange between soil and groundwater, at the local scale in an Alpine valley, a
micrometeorological station was installed during summer 2012 at Cividate Camuno (Oglio
river basin, Central Italian Alps, 274ma.s.l.), in a mountain environment with complex
orography and Alpine sublitoranean climate. The soil upper layers, lying on an anthropised
loose rock, are about 40cm deep and mainly covered by alfalfa (Medicago sativa), wild
carrot (Daucus carota) and yarrow (Achillea millefolium). The station is equipped
with longwave and shortwave radiometers, a thermo–hygrometer, two rain–gauges,
eddy correlation devices (Gill WindMaster sonic anemometer and Licor Li7500 gas
analyser, sampling at 20Hz), a TDR with multiplexer apparatus and four probes at
different depths, three soil–thermometers and a heat exchanger plate. Field and
laboratory tests were performed to characterise the main soil hydraulic properties
(i.e. hydraulic conductivity at saturation by means of infiltration tests and falling
head permeameter, porosity, residual water content and water content at saturation,
soil–water retention relationships, organic matter content and grain size distribution
curve).
Three different hypothesis to model the water exchange between soil–water and
groundwater were introduced. They are (i) a null exchange rate which accounts for a shortage
of precipitation and for representing the underlying soil as a capillary barrier, (ii) a pure
percolation with unitary gradient of the total hydraulic potential and (iii) a percolation or
water rise induced by an estimate of the local gradient on the basis of the measurements of
water content. As the lateral fluxes were negligible due to the site orography, accounting for
the measurement of rainfall, evapotranspiration and soil–water content, the closure of the
water balance allowed to assess the effectiveness of the different hypotheses to estimate the
exchange between soil–water and groundwater. The results shows that the water balance is
not closed without estimating the water exchange between soil and groundwater, but
assessing its value was found to be strongly sensitive to the accuracy of the adopted soil
model and constitutive laws. |
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