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| Titel |
Constraining model parameters on remotely sensed evaporation: justification for distribution in ungauged basins? |
| VerfasserIn |
H. C. Winsemius, H. H. G. Savenije, W. G. M. Bastiaanssen |
| 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 ; 12, no. 6 ; Nr. 12, no. 6 (2008-12-18), S.1403-1413 |
| Datensatznummer |
250010965
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| Publikation (Nr.) |
 copernicus.org/hess-12-1403-2008.pdf |
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| Zusammenfassung |
| In this study, land surface related parameter distributions of a conceptual
semi-distributed hydrological model are constrained by employing time
series of satellite-based evaporation estimates during the dry season
as explanatory information. The approach has been applied to the ungauged
Luangwa river basin (150 000 (km)2) in Zambia. The information
contained in these evaporation estimates imposes compliance of the model
with the largest outgoing water balance term, evaporation, and a spatially
and temporally realistic depletion of soil moisture within the dry season.
The model results in turn provide a better understanding of the information
density of remotely sensed evaporation. Model parameters to which evaporation
is sensitive, have been spatially distributed on the basis of dominant land
cover characteristics. Consequently, their values were conditioned by means
of Monte-Carlo sampling and evaluation on satellite evaporation estimates.
The results show that behavioural parameter sets for model units with similar
land cover are indeed clustered. The clustering reveals hydrologically
meaningful signatures in the parameter response surface: wetland-dominated
areas (also called dambos) show optimal parameter ranges that reflect
vegetation with a relatively small unsaturated zone (due to the shallow
rooting depth of the vegetation) which is easily moisture stressed. The
forested areas and highlands show parameter ranges that indicate a much
deeper root zone which is more drought resistent. Clustering was consequently
used to formulate fuzzy membership functions that can be used to constrain
parameter realizations in further calibration. Unrealistic parameter ranges,
found for instance in the high unsaturated soil zone values in the highlands
may indicate either overestimation of satellite-based evaporation or model
structural deficiencies. We believe that in these areas, groundwater uptake
into the root zone and lateral movement of groundwater should be included in
the model structure. Furthermore, a less distinct parameter clustering was
found for forested model units. We hypothesize that this is due to the
presence of two dominant forest types that differ substantially in their
moisture regime. This could indicate that the spatial discretization used
in this study is oversimplified. |
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