Choice of Pedotransfer Functions matters when simulating soil
water balance fluxes
L. Weihermüller*1,7, P. Lehmann2, M.
Herbst1, M. Rahmati3, A.
Verhoef4, D. Or2,5, D.
Jacques6, and H. Vereecken1,7
___________________________________________________________________________
1 Agrosphere Institute IBG 3, Forschungszentrum Jülich
GmbH, 52425 Jülich, Germany,
2 Department of Environmental Systems Science, ETH
Zurich, Switzerland
3 University of Maragheh, Department of Soil Science
and Engineering, Iran4 University of Reading, Department of Geography and
Environmental Science, Reading, UK
5 Division of Hydrologic Sciences (DHS) - Desert
Research Institute, Reno, NV, USA
6 Belgian Nuclear Research Centre SCK CEN, Institute
for Environment, Health and Safety (EHS), Mol, Belgium7 International Soil Modeling Consortium (ISMC),
Forschungszentrum Jülich GmbH, Jülich, Germany
*Corresponding author: Lutz Weihermüller, Forschungszentrum Jülich
IBG-3
Agrosphere Institute D-52425 Jülich, Voice: ++49 (0)2461 61 8669
email: l.weihermueller@fz-juelich.de
Abstract
Modelling of the land surface water-, energy-, and carbon balance
provides insight into the behaviour of the Earth System, under current
and future conditions. Currently, there exists a substantial variability
between model outputs, for a range of model types, whereby differences
between model input parameters could be an important reason. For
large-scale land surface, hydrological, and crop models, soil hydraulic
properties (SHP) are required as inputs, which are estimated from
pedotransfer functions (PTFs). To analyse the functional sensitivity of
widely used PTFs, the water fluxes for different scenarios using
HYDRUS-1D was simulated and predictions compared. The results showed
that using different PTFs causes substantial variability in predicted
fluxes. In addition, an in-depth analysis of the soil SHPs and derived
soil characteristics was performed to analyse why the SHPs
estimated from the different PTFs cause the model to behave differently.
The results obtained provide guidelines for the selection of PTFs in
large scale models. The model performance in terms of numerical
stability, time-integrated behaviour of cumulative fluxes, as well as
instantaneous fluxes was evaluated, in order to compare the suitability
of the PTFs. Based on this, the Rosetta, Wösten (), and Tóth PTF seem to
be the most robust PTFs for the Mualem van Genuchten SHPs and the PTF of
Cosby for the Brooks Corey functions. Based on our findings, we strongly
recommend to harmonize the PTFs used in model inter-comparison studies
to avoid artefacts originating from the choice of PTF rather from
different model structures.