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| Titel |
Uncertainty in the determination of soil hydraulic parameters and its influence on the performance of two hydrological models of different complexity |
| VerfasserIn |
G. Baroni, A. Facchi, C. Gandolfi, B. Ortuani, D. Horeschi, J. C. Dam |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 14, no. 2 ; Nr. 14, no. 2 (2010-02-09), S.251-270 |
| Datensatznummer |
250012180
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| Publikation (Nr.) |
 copernicus.org/hess-14-251-2010.pdf |
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| Zusammenfassung |
| Data of soil hydraulic properties forms often a limiting factor in
unsaturated zone modelling, especially at the larger scales. Investigations
for the hydraulic characterization of soils are time-consuming and costly,
and the accuracy of the results obtained by the different methodologies is
still debated. However, we may wonder how the uncertainty in soil hydraulic
parameters relates to the uncertainty of the selected modelling approach. We
performed an intensive monitoring study during the cropping season of a 10 ha
maize field in Northern Italy. The data were used to: i) compare different
methods for determining soil hydraulic parameters and ii) evaluate the effect of
the uncertainty in these parameters on different variables (i.e. evapotranspiration,
average water content in the root zone, flux at the
bottom boundary of the root zone) simulated by two hydrological models of
different complexity: SWAP, a widely used model of soil moisture dynamics in
unsaturated soils based on Richards equation, and ALHyMUS, a conceptual
model of the same dynamics based on a reservoir cascade scheme. We employed
five direct and indirect methods to determine soil hydraulic parameters for
each horizon of the experimental profile. Two methods were based on a
parameter optimization of: a) laboratory measured retention and hydraulic
conductivity data and b) field measured retention and hydraulic conductivity
data. The remaining three methods were based on the application of widely
used Pedo-Transfer Functions: c) Rawls and Brakensiek, d) HYPRES, and e) ROSETTA.
Simulations were performed using meteorological, irrigation and crop data
measured at the experimental site during the period June – October 2006.
Results showed a wide range of soil hydraulic parameter values generated
with the different methods, especially for the saturated hydraulic
conductivity Ksat and the shape parameter α of the van Genuchten curve.
This is reflected in a variability of the modeling results which is, as
expected, different for each model and each variable analysed. The
variability of the simulated water content in the root zone and of the
bottom flux for different soil hydraulic parameter sets is found to be often
larger than the difference between modeling results of the two models using
the same soil hydraulic parameter set. Also we found that a good agreement
in simulated soil moisture patterns may occur even if evapotranspiration and
percolation fluxes are significantly different. Therefore multiple output
variables should be considered to test the performances of methods and
models. |
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