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| Titel |
Macropore flow of old water revisited: experimental insights from a tile-drained hillslope |
| VerfasserIn |
J. Klaus, E. Zehe, M. Elsner, C. Külls, J. J. McDonnell |
| 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 ; 17, no. 1 ; Nr. 17, no. 1 (2013-01-16), S.103-118 |
| Datensatznummer |
250017678
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| Publikation (Nr.) |
 copernicus.org/hess-17-103-2013.pdf |
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| Zusammenfassung |
| The mechanisms allowing the rapid release of stored water to streams are
poorly understood. Here we use a tile-drained field site to combine
macroporous soils at the hillslope scale with the advantage of at least
partly controlled lower boundary conditions. We performed a series of three
irrigation experiments combining hydrometric measurements with stable
isotope and bromide tracers to better understand macropore–matrix
interactions and stored water release processes at the hillslope scale.
Stable isotope concentrations were monitored in the irrigation water, the
tile-drain discharge and the soil water before and after the experiment.
Bromide was measured every 5–15 min in the tile-drain hydrograph.
Different initial conditions for each experiment were used to examine how
these influenced flow and transport. Different amounts of irrigation water
were necessary to increase tile-drain discharge above the baseflow level.
Hydrograph separation based on bromide data revealed that irrigation water
contributions to peak tile-drain discharge were on the order of 20%.
Oxygen-18 and deuterium data were consistent with the bromide data and
showed that pre-event soil water contributed significantly to the tile-drain
event flow. However, the isotopic composition of soil water converged
towards the isotopic composition of irrigation water through the course of
the experiment. Mixing calculations revealed that by the end of the
irrigation experiments 20% of the soil water in the entire profile was
irrigation water. The isotopic data showed that the pre-event water in the
tile drain was mobilized in 20–40 cm soil depth where the macropore–matrix
interaction leads to an initiation of macropore flow after a moisture
threshold is exceeded. |
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