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| Titel |
Identifying flood recharge and inter-aquifer connectivity using multiple isotopes in subtropical Australia |
| VerfasserIn |
A. C. King, M. Raiber, D. I. Cendón, M. E. Cox, S. E. Hollins |
| 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. 5 ; Nr. 19, no. 5 (2015-05-19), S.2315-2335 |
| Datensatznummer |
250120713
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| Publikation (Nr.) |
 copernicus.org/hess-19-2315-2015.pdf |
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| Zusammenfassung |
| An understanding of hydrological processes is vital for the sustainable
management of groundwater resources, especially in areas where an aquifer
interacts with surface water systems or where aquifer interconnectivity
occurs. This is particularly important in areas that are subjected to
frequent drought/flood cycles, such as the Cressbrook Creek catchment in
Southeast Queensland, Australia. In order to understand the hydrological
response to flooding and to identify inter-aquifer connectivity, multiple
isotopes (δ2H, δ18O, 87Sr/86Sr, 3H
and 14C) were used in this study in conjunction with a comprehensive
hydrochemical assessment, based on data collected 6 months after severe
flooding in 2011. The relatively depleted stable isotope signatures of the
flood-generating rainfall (δ2H: −30.2 to −27.8‰,
δ18O: −5.34 to −5.13‰ VSMOW) were evident in surface
water samples (δ2H: −25.2 to −23.2‰, δ18O:
−3.9 to −3.6‰ VSMOW), indicating that these extreme events were
a major source of recharge to the dam in the catchment headwaters.
Furthermore, stable isotopes confirmed that the flood generated significant
recharge to the alluvium in the lower part of the catchment, particularly in
areas where interactions between surface waters and groundwater were
identified and where diffuse aquifer recharge is normally limited by a thick
(approximately 10 m) and relatively impermeable unsaturated zone. However,
in the upper parts of the catchment where recharge generally occurs more
rapidly due to the dominance of coarse-grained sediments in the unsaturated
zone, the stable isotope signature of groundwater resembles the longer-term
average rainfall values (δ2H: −12.6, δ18O:
−3.4‰ VSMOW), highlighting that recharge was sourced
from smaller rainfall events that occurred subsequent to the flooding.
Interactions between the bedrock aquifers and the alluvium were identified
at several sites in the lower part of the catchment based on
87Sr/86Sr ratios; this was also supported by the hydrochemical
assessment, which included the modelling of evaporation trends and
saturation indices. The integrated approach used in this study facilitated
the identification of hydrological processes over different spatial and
temporal scales, and the method can be applied to other complex geological
settings with variable climatic conditions. |
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