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| Titel |
A multi basin SWAT model analysis of runoff and sedimentation in the Blue Nile, Ethiopia |
| VerfasserIn |
Z. M. Easton, D. R. Fuka, E. D. White, A. S. Collick, B. Biruk Ashagre, M. McCartney, S. B. Awulachew, A. A. Ahmed, T. S. Steenhuis |
| 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 (2010-10-11), S.1827-1841 |
| Datensatznummer |
250012438
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| Publikation (Nr.) |
 copernicus.org/hess-14-1827-2010.pdf |
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| Zusammenfassung |
| A multi basin analysis of runoff and erosion in the Blue Nile Basin,
Ethiopia was conducted to elucidate sources of runoff and sediment. Erosion
is arguably the most critical problem in the Blue Nile Basin, as it limits
agricultural productivity in Ethiopia, degrades benthos in the Nile, and
results in sedimentation of dams in downstream countries. A modified version
of the Soil and Water Assessment Tool (SWAT) model was developed to predict
runoff and sediment losses from the Ethiopian Blue Nile Basin. The model
simulates saturation excess runoff from the landscape using a simple daily
water balance coupled to a topographic wetness index in ways that are
consistent with observed runoff processes in the basin. The spatial
distribution of landscape erosion is thus simulated more correctly. The
model was parameterized in a nested design for flow at eight and sediment at
three locations in the basin. Subbasins ranged in size from 1.3 to
174 000 km2, and interestingly, the partitioning of runoff and infiltrating
flow could be predicted by topographic information. Model predictions showed
reasonable accuracy (Nash Sutcliffe Efficiencies ranged from 0.53–0.92) with
measured data across all sites except Kessie, where the water budget could
not be closed; however, the timing of flow was well captured. Runoff losses
increased with rainfall during the monsoonal season and were greatest from
areas with shallow soils and large contributing areas. Analysis of model
results indicate that upland landscape erosion dominated sediment delivery
to the main stem of the Blue Nile in the early part of the growing season
when tillage occurs and before the soil was wetted up and plant cover was
established. Once plant cover was established in mid August landscape
erosion was negligible and sediment export was dominated by channel
processes and re-suspension of landscape sediment deposited early in the
growing season. These results imply that targeting small areas of the
landscape where runoff is produced can be the most effective at controlling
erosion and protecting water resources. However, it is not clear what can be
done to manage channel erosion, particularly in first order streams in the
basin. |
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