Assessment of Key Transport Parameters in a Karst System Under Different Dynamic Conditions Based on Tracer Experiments: the Jeita Karst System, Lebanon

Citation

Material Information

Title:
Assessment of Key Transport Parameters in a Karst System Under Different Dynamic Conditions Based on Tracer Experiments: the Jeita Karst System, Lebanon
Series Title:
Hydrogeology Journal
Creator:
Doummar, Joanna
Margane, Armin
Geyer, Tobias
Sauter, Martin
Publisher:
Springer Nature
Publication Date:
Language:
English

Subjects

Subjects / Keywords:
Tracer Tests ( local )
Two-Region Nonequilibrium Model ( local )
Karst ( local )
Lebanon ( local )
Genre:
serial ( sobekcm )

Notes

Abstract:
Artificial tracer experiments were conducted in the mature karst system of Jeita (Lebanon) under various flow conditions using surface and subsurface tracer injection points, to determine the variation of transport parameters (attenuation of peak concentration, velocity, transit times, dispersivity, and proportion of immobile and mobile regions) along fast and slow flow pathways. Tracer breakthrough curves (TBCs) observed at the karst spring were interpreted using a two-region nonequilibrium approach (2RNEM) to account for the skewness in the TBCs’ long tailings. The conduit test results revealed a discharge threshold in the system dynamics, beyond which the transport parameters vary significantly. The polynomial relationship between transport velocity and discharge can be related to the variation of the conduit’s cross-sectional area. Longitudinal dispersivity in the conduit system is not a constant value (α = 7–10 m) and decreases linearly with increasing flow rate because of dilution effects. Additionally, the proportion of immobile regions (arising from conduit irregularities) increases with decreasing water level in the conduit system. From tracer tests with injection at the surface, longitudinal dispersivity values are found to be large (8–27 m). The tailing observed in some TBCs is generated in the unsaturated zone before the tracer actually arrives at the major subsurface conduit draining the system. This work allows the estimation and prediction of the key transport parameters in karst aquifers. It shows that these parameters vary with time and flow dynamics, and they reflect the geometry of the flow pathway and the origin of infiltrating (potentially contaminated) recharge.
Original Version:
Hydrogeology Journal, Vol. 26, no. 7 (2018-03-28).

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University of South Florida Library
Holding Location:
University of South Florida
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This object is protected by copyright, and is made available here for research and educational purposes. Permission to reuse, publish, or reproduce the object beyond the bounds of Fair Use or other exemptions to copyright law must be obtained from the copyright holder.

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