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| Titel |
On the value of combined event runoff and tracer analysis to improve understanding of catchment functioning in a data-scarce semi-arid area |
| VerfasserIn |
M. Hrachowitz, R. Bohte, M. L. Mul, T. A. Bogaard, H. H. G. Savenije, 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 ; 15, no. 6 ; Nr. 15, no. 6 (2011-06-27), S.2007-2024 |
| Datensatznummer |
250012866
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| Publikation (Nr.) |
 copernicus.org/hess-15-2007-2011.pdf |
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| Zusammenfassung |
| Hydrological processes in small catchments are not quite understood yet,
which is true in particular for catchments in data scarce, semi-arid
regions. This is in contrast with the need for a better understanding of
water fluxes and the interactions between surface- and groundwater in order
to facilitate sustainable water resources management in such environments,
where both floods and droughts can result in severe crop loss. In this
study, event runoff coefficient analysis and limited tracer data of four
small, nested sub-catchments (0.4–25.3 km2) in a data scarce,
semi-arid region of Tanzania helped to characterize the distinct response of
the study catchments and to gain insights into the dominant runoff
processes. The estimated event runoff coefficients were very low and did not
exceed 0.09. They were found to be significantly related to the 5-day
antecedent precipitation totals as well as to base flow, indicating a close
relation to changes in soil moisture and thus potential switches in runoff
generation processes. The time scales of the "direct flow" reservoirs,
used to compute the event runoff coefficients, were up to one order of
magnitude reduced for extreme events, compared to "average" events,
suggesting the activation of at least a third flow component, besides base-
and direct flow, assumed to be infiltration overland flow. Analysis of
multiple tracers highlighted the importance of pre-event water to total
runoff, even during intense and high yield precipitation events. It further
illustrated the distinct nature of the catchments, in particular with
respect to the available water storage, which was suggested by different
degrees of tracer damping in the individual streams. The use of multiple
tracers subsequently allowed estimating uncertainties in hydrograph
separations arising from the use of different tracers. The results highlight
the presence of considerable uncertainties, emphasizing the need for
multiple tracers in order to avoid misleading results. This study shows the
value of hydrological data collection over one whole wet season using
multi-tracers to improve the understanding of hydrological functioning and
thus for water resources management in data scarce, semi-arid environments. |
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