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| Titel |
Using 14C and 3H to understand groundwater flow and recharge in an aquifer window |
| VerfasserIn |
A. P. Atkinson, I. Cartwright, B. S. Gilfedder, D. I. Cendón, N. P. Unland, H. Hofmann |
| 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 ; 18, no. 12 ; Nr. 18, no. 12 (2014-12-09), S.4951-4964 |
| Datensatznummer |
250120551
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| Publikation (Nr.) |
 copernicus.org/hess-18-4951-2014.pdf |
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| Zusammenfassung |
| Knowledge of groundwater residence times and recharge locations is vital to
the sustainable management of groundwater resources. Here we investigate
groundwater residence times and patterns of recharge in the Gellibrand
Valley, southeast Australia, where outcropping aquifer sediments of the
Eastern View Formation form an "aquifer window" that may receive diffuse
recharge from rainfall and recharge from the Gellibrand River. To determine
recharge patterns and groundwater flow paths, environmental isotopes
(3H, 14C, δ13C, δ18O, δ2H)
are used in conjunction with groundwater geochemistry and continuous
monitoring of groundwater elevation and electrical conductivity. The water
table fluctuates by 0.9 to 3.7 m annually, implying recharge rates of 90 and
372 mm yr−1. However, residence times of shallow (11 to 29 m)
groundwater determined by 14C are between 100 and 10 000 years, 3H
activities are negligible in most of the groundwater, and groundwater
electrical conductivity remains constant over the period of study. Deeper
groundwater with older 14C ages has lower δ18O values than
younger, shallower groundwater, which is consistent with it being derived
from greater altitudes. The combined geochemistry data indicate that local
recharge from precipitation within the valley occurs through the aquifer
window, however much of the groundwater in the Gellibrand Valley
predominantly originates from the regional recharge zone, the Barongarook
High. The Gellibrand Valley is a regional discharge zone with upward head
gradients that limits local recharge to the upper 10 m of the aquifer.
Additionally, the groundwater head gradients adjacent to the Gellibrand
River are generally upwards, implying that it does not recharge the
surrounding groundwater and has limited bank storage. 14C ages and Cl
concentrations are well correlated and Cl concentrations may be used to
provide a first-order estimate of groundwater residence times. Progressively
lower chloride concentrations from 10 000 years BP to the present day are
interpreted to indicate an increase in recharge rates on the Barongarook
High. |
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