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| Titel |
Influence of aquifer geometry on karst hydraulics using different distributive modeling approaches |
| VerfasserIn |
Sandra Oehlmann, Tobias Geyer, Tobias Licha, Steffen Birk |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250082243
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| Zusammenfassung |
| The simulation of flow and transport processes in karst systems is a challenge due to the
unknown location of highly conductive karst conduit networks.
In this work, the influence of aquifer geometry, particularly the geometry of highly
conductive discrete elements, on three-dimensional groundwater flow in a large-scale aquifer
system is examined. The area of investigation comprises several springs on the
Western Swabian Alb / Germany and has an area of approximately 150 km2. The
largest spring therein is the Gallusquelle with an annual average discharge of 0.5
m3/s. Long-term spring hydrographs and hydraulic head measurements, as well
as several tracer tests, are available from previous work and are used for model
calibration.
Four distributive continuum and discrete flow models with different degrees of
complexity were set-up employing the finite element simulation software Comsol
Multiphysics®. Stationary groundwater flow equations were implemented for single
continuum and hybrid modeling. The aquifer geometry was modeled previously with the
software Geological Objects Computer Aided Design® (GoCAD®) and transferred to
Comsol® software.
Simulation results show that not only the location of karst conduits but also their
geometry has significant impact on the simulated spring discharge and hydraulic head
distribution. A constant conduit radius leads to distorted hydraulic head contour lines and a
conduit restrained flow regime close to the spring, while a linearly increasing radius towards
the spring leads to evenly distributed contour lines. Models with such an increase in conduit
diameters allow the simulation of annual discharge for several springs. This result is in
agreement with synthetic karst genesis models, which suggest an increase of conduit
diameters towards karst springs because of a positive correlation between flow
rates and carbonate solution. The software Comsol Multiphysics®, while rarely
used for groundwater flow modeling, was found to meet all requirements for karst
modeling and thus represents a promising, extendable tool for further modeling studies. |
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