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| Titel |
Water balance modeling of Upper Blue Nile catchments using a top-down approach |
| VerfasserIn |
S. Tekleab, S. Uhlenbrook, Y. Mohamed, H. H. G. Savenije, M. Temesgen, J. Wenninger |
| 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 ; 15, no. 7 ; Nr. 15, no. 7 (2011-07-13), S.2179-2193 |
| Datensatznummer |
250012887
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| Publikation (Nr.) |
 copernicus.org/hess-15-2179-2011.pdf |
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| Zusammenfassung |
The water balances of twenty catchments in the Upper Blue Nile basin have
been analyzed using a top-down modeling approach based on Budyko's
hypotheses. The objective of this study is to obtain better understanding of
water balance dynamics of upper Blue Nile catchments on annual and monthly
time scales and on a spatial scale of meso scale to large scale. The water
balance analysis using a Budyko-type curve at annual scale reveals that the
aridity index does not exert a first order control in most of the
catchments. This implies the need to increase model complexity to monthly
time scale to include the effects of seasonal soil moisture dynamics. The
dynamic water balance model used in this study predicts the direct runoff
and other processes based on the limit concept; i.e. for dry environments
since rainfall amount is small, the aridity index approaches to infinity or
equivalently evaporation approaches rainfall and for wet environments where
the rainfall amount is large, the aridity index approaches to zero and
actual evaporation approaches the potential evaporation. The uncertainty of
model parameters has been assessed using the GLUE (Generalized Likelihood
Uncertainty Estimation) methodology. The results show that the majority of
the parameters are reasonably well identifiable. However, the baseflow
recession constant was poorly identifiable. Parameter uncertainty and model
structural errors could be the reason for the poorly identifiable parameter.
Moreover, a multi-objective model calibration strategy has been employed to
emphasize the different aspects of the hydrographs on low and high flows.
The model has been calibrated and validated against observed streamflow time
series and it shows good performance for the twenty study catchments in the
upper Blue Nile. During the calibration period (1995–2000) the Nash and
Sutcliffe efficiency (E NS) for monthly flow prediction varied between
0.52 to 0.93 (dominated by high flows), while it varied between 0.32 to 0.90
using logarithms of flow series (indicating the goodness of low flow
simulations). The model is parsimonious and it is suggested that the
calibrated parameters could be used after some more regionalization efforts
to predict monthly stream flows in ungauged catchments of the Upper Blue
Nile basin, which is the vast majority of catchments in that region. |
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