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| Titel |
Modelling conduit-matrix exchange processes in a karst aquifer |
| VerfasserIn |
J. Kordilla, T. Geyer, T. Graf, M. Sauter |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250021453
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| Zusammenfassung |
| The objective of this work is to identify the relevance of gradient exchange between karst
conduits and fissured matrix for interpretation of karst spring responses. The numerical
control volume finite element FRAC3DVS/HydroGeoSphere model (Therrien and Sudicky
1996) is used to simulate discharge and transport signals (18O) at the karst spring
Gallusquelle (Swabian Alb, South Germany) for a period of two years. The chosen double
continuum approach accounts for saturated and unsaturated flow conditions in the karst
system. Important model parameters were identified using sensitivity analyses. Model input
was generated using a soil-moisture balance approach that accounts for evaporation,
interception and snow storage (Geyer 2008). In general, karst aquifers are characterized by a
dual flow system consisting of a low permeability matrix with high storage and a secondary
system of highly conductive conduits with low storage. The interaction between both systems
represents one of the characteristics of karst aquifers, displayed especially after
recharge events, i.e. a characteristic rapid increase in discharge and slow recession.
A further important indicator is the variation of isotopic spring signals, e.g. the
relative abundance of 18O in spring water. During long-term recession, a systematic
decrease in 18O was observed, which is interpreted as the release of isotopically
lighter water, recharged during the winter period several years ago. It is believed
that this behaviour can be related to: (1) gradient inversion during high recharge
conditions and (2) storage in the matrix system and subsequent release of water. |
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