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| Titel |
Understanding runoff processes in a semi-arid environment through isotope and hydrochemical hydrograph separations |
| VerfasserIn |
V. V. Camacho Suarez, A. M. L. Saraiva Okello, J. W. Wenninger, S. Uhlenbrook |
| 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 ; 19, no. 10 ; Nr. 19, no. 10 (2015-10-20), S.4183-4199 |
| Datensatznummer |
250120827
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| Publikation (Nr.) |
 copernicus.org/hess-19-4183-2015.pdf |
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| Zusammenfassung |
| The understanding of runoff generation mechanisms is crucial for the
sustainable management of river basins such as the allocation of water
resources or the prediction of floods and droughts. However, identifying the
mechanisms of runoff generation has been a challenging task, even more so in
arid and semi-arid areas where high rainfall and streamflow variability, high
evaporation rates, and deep groundwater reservoirs may increase the
complexity of hydrological process dynamics. Isotope and hydrochemical
tracers have proven to be useful in identifying runoff components and their
characteristics. Moreover, although widely used in humid temperate regions,
isotope hydrograph separations have not been studied in detail in arid and
semi-arid areas. Thus the purpose of this study is to determine whether
isotope hydrograph separations are suitable for the quantification and
characterization of runoff components in a semi-arid catchment considering
the hydrological complexities of these regions. Through a hydrochemical
characterization of the surface water and groundwater sources of the
catchment and two- and three-component hydrograph separations, runoff
components of the Kaap catchment in South Africa were quantified using both
isotope and hydrochemical tracers. No major disadvantages while using isotope
tracers over hydrochemical tracers were found. Hydrograph separation results
showed that runoff in the Kaap catchment is mainly generated by groundwater
sources. Two-component hydrograph separations revealed groundwater
contributions of between 64 and 98 % of total runoff. By means of
three-component hydrograph separations, runoff components were further
separated into direct runoff, shallow and deep groundwater components. Direct
runoff, defined as the direct precipitation on the stream channel and
overland flow, contributed up to 41 % of total runoff during wet catchment
conditions. Shallow groundwater defined as the soil water and near-surface
water component (and potentially surface runoff) contributed up to 45 % of
total runoff, and deep groundwater contributed up to 84 % of total runoff.
A strong correlation for the four studied events was found between the
antecedent precipitation conditions and direct runoff. These findings suggest
that direct runoff is enhanced by wetter conditions in the catchment that
trigger saturation excess overland flow as observed in the hydrograph
separations. |
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