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| Titel |
The significance and lag-time of deep through flow: an example from a small, ephemeral catchment with contrasting soil types in the Adelaide Hills, South Australia |
| VerfasserIn |
E. Bestland, S. Milgate, D. Chittleborough, J. VanLeeuwen, M. Pichler, L. Soloninka |
| 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 ; 13, no. 7 ; Nr. 13, no. 7 (2009-07-16), S.1201-1214 |
| Datensatznummer |
250011940
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| Publikation (Nr.) |
 copernicus.org/hess-13-1201-2009.pdf |
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| Zusammenfassung |
| The importance of deep soil-regolith through flow in a small (3.4 km2)
ephemeral catchment in the Adelaide Hills of South Australia was
investigated by detailed hydrochemical analysis of soil water and stream
flow during autumn and early winter rains. In this Mediterranean climate
with strong summer moisture deficits, several significant rainfalls are
required to generate soil through flow and stream flow [in ephemeral
streams]. During autumn 2007, a large (127 mm) drought-breaking rain
occurred in April followed by significant May rains; most of this April and
May precipitation occurred prior to the initiation of stream flow in late
May. These early events, especially the 127 mm April event, had low stable
water isotope values compared with later rains during June and July and
average winter precipitation. Thus, this large early autumn rain event with
low isotopic values (δ18O, δD) provided an excellent
natural tracer. During later June and July rainfall events, daily stream and
soil water samples were collected and analysed. Results from major and trace
elements, water isotopes (δ18O, δD), and dissolved
organic carbon analysis clearly demonstrate that a large component of this
early April and May rain was stored and later pushed out of deep soil and
regolith zones. This pre-event water was identified in the stream as well as
identified in deep soil horizons due to its different isotopic signature
which contrasted sharply with the June–July event water. Based on this data,
the soil-regolith hydrologic system for this catchment has been re-thought.
The catchment area consists of about 60% sandy and 40% clayey soils.
Regolith flow in the sandy soil system and not the clayey soil system is now
thought to dominate the deep subsurface flow in this catchment. The clayey
texture contrast soils had rapid response to rain events and saturation
excess overland flow. The sandy soils had delayed soil through flow and
infiltration excess overland flow. A pulse of macropore through flow was
observed in the sandy soils three days after the rainfall event largely
ended. The macropore water was a mixture of pre-event and event water,
demonstrating the lag-time and mixing of the water masses in the sandy soil
system. By contrast, the clayey soil horizons were not dominated by
pre-event water, demonstrating the quicker response and shallow through flow
of the clayey soil system. Thus, the sandy terrain has a greater vadose zone
storage and greater lag time of through flow than the clayey terrain. |
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