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Titel |
Reduction of the ambiguity of karst aquifer modeling through pattern matching of groundwater flow and transport |
VerfasserIn |
Sandra Oehlmann, Tobias Geyer, Tobias Licha, Martin Sauter |
Konferenz |
EGU General Assembly 2014
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 16 (2014) |
Datensatznummer |
250096107
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Publikation (Nr.) |
EGU/EGU2014-11593.pdf |
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Zusammenfassung |
Distributive numerical simulations are an effective, process-based method for predicting
groundwater resources and quality. They are based on conceptual hydrogeological models
that characterize the properties of the catchment area and aquifer. Karst systems play an
important role in water supply worldwide. Conceptual models are however difficult to build
because of the highly developed heterogeneity of the systems. The geometry and
properties of highly conductive karst conduits are generally unknown and difficult to
characterize with field experiments. Due to these uncertainties numerical models
of karst areas usually cannot simulate the hydraulic head distribution in the area,
spring discharge and tracer breakthrough curves simultaneously on catchment scale.
Especially in complex hydrogeological systems, this approach would reduce model
ambiguity, which is prerequisite to predict groundwater resources and pollution
risks.
In this work, a distributive numerical groundwater flow and transport model was
built for a highly heterogeneous karst aquifer in south-western Germany. For this
aim, a solute transport interface for one-dimensional pipes was implemented in the
software Comsol Multiphysics® and coupled to the standard three-dimensional solute
transport interface for domains. The model was calibrated and hydraulic parameters
could be obtained. The simulation was matched to the steady-state hydraulic head
distribution in the model area, the spring discharge of several springs and the transport
velocities of two tracer tests. Furthermore, other measured parameters such as hydraulic
conductivity of the fissured matrix and the maximal karst conduit volume were
available for model calibration. Parameter studies were performed for several karst
conduit geometries to analyze their influence in a large-scale heterogeneous karst
system.
Results show that it is not only possible to derive a consistent flow and transport model
for a 150km2 karst area to be employed as a prognostic tool but that the combined use of
groundwater flow and transport parameters greatly reduces model ambiguity. The
approach provides basic information about the conduit network not accessible for direct
geometric measurements. The conduit network volume for the main karst spring
in the study area could be narrowed down to approximately 100000m3, even
though standard tracer test evaluations predicted a volume of up to 200000m3. |
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