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| Titel |
Analyzing catchment behavior through catchment modeling in the Gilgel Abay, Upper Blue Nile River Basin, Ethiopia |
| VerfasserIn |
S. Uhlenbrook, Y. Mohamed, A. S. Gragne |
| 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. 10 ; Nr. 14, no. 10 (2010-10-29), S.2153-2165 |
| Datensatznummer |
250012460
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| Publikation (Nr.) |
 copernicus.org/hess-14-2153-2010.pdf |
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| Zusammenfassung |
| Understanding catchment hydrological processes is essential for water
resources management, in particular in data scarce regions. The Gilgel Abay
catchment (a major tributary into Lake Tana, source of the Blue Nile) is
undergoing intensive plans for water management, which is part of larger
development plans in the Blue Nile basin in Ethiopia. To obtain a better
understanding of the water balance dynamics and runoff generation mechanisms
and to evaluate model transferability, catchment modeling has been conducted
using the conceptual hydrological model HBV. Accordingly, the catchment of
the Gilgel Abay has been divided into two gauged sub-catchments (Upper
Gilgel Abay and Koga) and the un-gauged part of the catchment. All available
data sets were tested for stationarity, consistency and homogeneity and the
data limitations (quality and quantity) are discussed.
Manual calibration of the daily models for three different catchment
representations, i.e. (i) lumped, (ii) lumped with multiple vegetation
zones, and (iii) semi-distributed with multiple vegetation and elevation
zones, showed good to satisfactory model performances with Nash-Sutcliffe
efficiencies Reff > 0.75 and > 0.6 for the Upper Gilgel
Abay and Koga sub-catchments, respectively. Better model results could not
be obtained with manual calibration, very likely due to the limited data
quality and model insufficiencies. Increasing the computation time step to
15 and 30 days improved the model performance in both sub-catchments to
Reff > 0.8. Model parameter transferability tests have been
conducted by interchanging parameters sets between the two gauged
sub-catchments. Results showed poor performances for the daily models
(0.30 < Reff < 0.67), but better performances for the 15 and 30 days
models, Reff > 0.80. The transferability tests together with a
sensitivity analysis using Monte Carlo simulations (more than 1 million
model runs per catchment representation) explained the different hydrologic
responses of the two sub-catchments, which seems to be mainly caused by the
presence of dambos in Koga sub-catchment. It is concluded that daily model
transferability is not feasible, while it can produce acceptable results for
the 15 and 30 days models. This is very useful for water resources planning
and management, but not sufficient to capture detailed hydrological
processes in an ungauged area. |
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