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| Titel |
Representation of water abstraction from a karst conduit with numerical discrete-continuum models |
| VerfasserIn |
T. Reimann, M. Giese, T. Geyer, R. Liedl, J. C. Maréchal, W. B. Shoemaker |
| 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 ; 18, no. 1 ; Nr. 18, no. 1 (2014-01-17), S.227-241 |
| Datensatznummer |
250120254
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| Publikation (Nr.) |
 copernicus.org/hess-18-227-2014.pdf |
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| Zusammenfassung |
Karst aquifers are characterized by highly conductive conduit flow paths
embedded in a less conductive fissured and fractured matrix, resulting in
strong permeability contrasts with structured heterogeneity and anisotropy.
Groundwater storage occurs predominantly in the fissured matrix. Hence, most
mathematical karst models assume quasi-steady-state flow in conduits
neglecting conduit-associated drainable storage (CADS). The concept of CADS
considers storage volumes, where karst water is not part of the active flow
system but hydraulically connected to conduits (for example karstic voids
and large fractures). The disregard of conduit storage can be inappropriate
when direct water abstraction from karst conduits occurs, e.g., large-scale
pumping. In such cases, CADS may be relevant. Furthermore, the typical
fixed-head boundary condition at the karst outlet can be inadequate for
water abstraction scenarios because unhampered water inflow is possible.
The objective of this work is to analyze the significance of CADS and
flow-limited boundary conditions on the hydraulic behavior of karst aquifers
in water abstraction scenarios. To this end, the numerical
discrete-continuum model MODFLOW-2005 Conduit Flow Process Mode 1 (CFPM1) is
enhanced to account for CADS. Additionally, a fixed-head limited-flow (FHLQ)
boundary condition is added that limits inflow from constant head boundaries
to a user-defined threshold. The effects and the proper functioning of these
modifications are demonstrated by simplified model studies. Both
enhancements, CADS and FHLQ boundary, are shown to be useful for water
abstraction scenarios within karst aquifers. An idealized representation of
a large-scale pumping test in a karst conduit is used to demonstrate that
the enhanced CFPM1 is able to adequately represent water abstraction
processes in both the conduits and the matrix of real karst systems, as
illustrated by its application to the Cent Fonts karst system. |
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