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| Titel |
Incorporating soil variability in continental soil water modelling: a trade-off between data availability and model complexity |
| VerfasserIn |
L. Peeters, R. S. Crosbie, R. Doble, A. I. J. M. Van Dijk |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250059968
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| Zusammenfassung |
| Developing a continental land surface model implies finding a balance between the
complexity in representing the system processes and the availability of reliable
data to drive, parameterise and calibrate the model. While a high level of process
understanding at plot or catchment scales may warrant a complex model, such data
is not available at the continental scale. This data sparsity is especially an issue
for the Australian Water Resources Assessment system, AWRA-L, a land-surface
model designed to estimate the components of the water balance for the Australian
continent.
This study focuses on the conceptualization and parametrization of the soil drainage
process in AWRA-L. Traditionally soil drainage is simulated with Richards’ equation, which
is highly non-linear. As general analytic solutions are not available, this equation is usually
solved numerically. In AWRA-L however, we introduce a simpler function based on
simulation experiments that solve Richards’ equation. In the simplified function soil drainage
rate, the ratio of drainage (D) over storage (S), decreases exponentially with relative water
content. This function is controlled by three parameters, the soil water storage at field
capacity (SFC), the drainage fraction at field capacity (KFC) and a drainage function
exponent (β).
[ ]
D- -S–
S = KF C exp - β (1 - SFC )
To obtain spatially variable estimates of these three parameters, the Atlas of
Australian Soils is used, which lists soil hydraulic properties for each soil profile
type. For each soil profile type in the Atlas, 10 days of draining an initially fully
saturated, freely draining soil is simulated using HYDRUS-1D. With field capacity
defined as the volume of water in the soil after 1 day, the remaining parameters can
be obtained by fitting the AWRA-L soil drainage function to the HYDRUS-1D
results.
This model conceptualisation fully exploits the data available in the Atlas of Australian
Soils, without the need to solve the non-linear Richards’ equation for each time-step.
The spatial distribution of long term recharge and baseflow obtained with a 30
year simulation of historic data using this parameterisation, corresponds well with
the spatial patterns of groundwater recharge inferred from field measurements. |
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