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| Titel |
Hydrological modelling of an artificial headwater catchment using the model system WaSiM-ETH |
| VerfasserIn |
H. Hölzel, B. Diekkrüger |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250020990
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| Zusammenfassung |
| The hydrological headwater catchment Chicken Creek (6.5 ha) was constructed in a lignite
open-cast mine by Cottbus (Germany) to study initial processes of ecosystem development.
The catchment has been intensively monitored for more than three years. Thereby, it is well
suited to test and develop hydrological models. The construction of a clay layer in the
basement simplifies the balancing of the water cycle since lateral inflows and vertical
outflows can be neglected.
For modelling purposes all basic input data were given, but neither discharge nor soil
moisture measurements were provided. Hence, no high model quality can be feigned by
fitting simulated results on observed output data.
To compare the ability of different models and modellers to describe the hydrological
behaviour of that catchment, a model competition was declared, on which several
international scientists take part, all specialised in hydrological modelling. The contest is
conducted in different levels, whereupon the knowledge of modellers concerning the
investigated catchment will be increased stepwise. All modellers use the same database and
results will be evaluated by an independent observer group. Thereby, the comparability
between different model applications is guaranteed.
We applied the process-based distributed Water balance Simulation Model (WaSiM-ETH)
by Schulla & Jasper (2007) to simulate the first three years since the catchment construction
was finished (Sep. 2005Â –Â Aug. 2008).
For the first modelling exercise important initial conditions (e.g. soil moisture) were
unknown. Due to the lack of field experiences, effects of a constructed lake were disregarded.
Therefore, the results of the first level were far away from being perfect, e.g. discharge was
simulated from the beginning which was not observed because in reality soil water and lake
storages were filled up first.
The biggest differences occurred between simulated and observed surface runoff. In
reality, surface runoff is the dominant runoff part responsible for approximately 70Â % of the
total runoff, but only half a percent was simulated. Hence, runoff dynamic and runoff peaks
were underestimated. The simulated result is physically vindicated through the
given data, because the sandy soils (sand content of 70Â –Â 90Â %) leads to high
infiltration rates. During a first survey a compact and sealed layer was identified
as the reason for high surface runoff, which could not be derived from the given
date.
For the second step of the modelling exercise the lake and the improved knowledge about
the initial conditions were considered. Now, the simulated discharge shows the same delay as
observed. Furthermore, effects of the sealed layer could be considered by a differentiated
representation of soil conditions. Thereby, the simulated surface runoff increased up
to 60Â % of total runoff, which leads to an enforced runoff dynamic with higher
peaks.
Now, it is up to the observer group to evaluate whether or not the simulated results of the
second modelling level has improved. |
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