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| Titel |
Rainfall-runoff modelling and palaeoflood hydrology applied to reconstruct centennial scale records of flooding and aquifer recharge in ungauged ephemeral rivers |
| VerfasserIn |
G. Benito, B. A. Botero, V. R. Thorndycraft, M. Rico, Y. Sánchez-Moya, A. Sopeña, M. J. Machado, O. Dahan |
| 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. 4 ; Nr. 15, no. 4 (2011-04-08), S.1185-1196 |
| Datensatznummer |
250012745
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| Publikation (Nr.) |
 copernicus.org/hess-15-1185-2011.pdf |
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| Zusammenfassung |
| In this study we propose a multi-source data approach for
quantifying long-term flooding and aquifer recharge in ungauged ephemeral
rivers. The methodology is applied to the Buffels River, at 9000 km2
the largest ephemeral river in Namaqualand (NW South Africa), a region with
scarce stream flow records limiting research investigating hydrological
response to global change. Daily discharge and annual flood series
(1965–2006) were estimated from a distributed rainfall-runoff hydrological
model (TETIS) using rainfall gauge records located within the catchment. The
model was calibrated and validated with data collected during a two year
monitoring programme (2005–2006) at two stream flow stations, one each in
the upper and lower reaches of the catchment. In addition to the modelled
flow records, non-systematic flood data were reconstructed using both
sedimentary and documentary evidence. The palaeoflood record identified at
least 25 large floods during the last 700 yr; with the largest floods
reaching a minimum discharge of 255 m3 s−1 (450 yr return
period) in the upper basin, and 510 m3 s−1 (100 yr return period)
in the lower catchment. Since AD 1925, the flood hydrology of the Buffels
River has been characterised by a decrease in the magnitude and frequency of
extreme floods, with palaeoflood discharges (period 1500–1921) five times
greater than the largest modelled floods during the period 1965–2006. Large
floods generated the highest hydrograph volumes, however their contribution
to aquifer recharge is limited as this depends on other factors such as
flood duration and storage capacity of the unsaturated zone prior to the
flood. Floods having average return intervals of 5–10 yr (120–140 m3 s−1)
and flowing for 12 days are able to fully saturate the
Spektakel aquifer in the lower Buffels River basin. Alluvial aquifer storage
capacity limiting potential recharge by the largest floods is a common
problem in arid environments, with the largest infiltration volumes favoured
by increasing depth to groundwater levels. |
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