Preprints
https://doi.org/10.5194/hess-2024-46
https://doi.org/10.5194/hess-2024-46
22 Mar 2024
 | 22 Mar 2024
Status: this preprint is currently under review for the journal HESS.

Karst aquifer discharge response to rainfall interpreted as anomalous transport

Dan Elhanati, Nadine Goeppert, and Brian Berkowitz

Abstract. The discharge measured in karst springs is known to exhibit distinctive long tails during recession times following distinct discharge peaks of short duration. The long-tail behavior is generally attributed to the occurrence of tortuous, ramified flow paths that develop in the underground structure of karst systems. Modeling the discharge behavior poses unique difficulties because of the poorly-delineated flow path geometry and generally scarce information on the hydraulic properties of catchment-scale systems. In a different context, modeling of long-tailed behavior has been addressed in studies of chemical transport. Here, an adaptation of a continuous time random walk – particle tracking (CTRW-PT) framework for anomalous transport is proposed, which offers a robust means to quantify long-tailed breakthrough curves that often arise during chemical species transport under various flow scenarios. A theoretical analogy is first established between partially water-saturated karst flow, characterized by temporally varying water storage, and chemical transport involving accumulation and release of a chemical tracer. This analogy is then used to develop and implement a CTRW-PT model. Application of this numerical model to examination of three years of summer rainfall and discharge data from a karst aquifer system – the Disnergschroef high alpine site in the Austrian Alps – is shown to yield robust fits between modeled and measured discharge values. In particular, the analysis underscores the predominance of slow diffusive flow over rapid conduit flow. The study affirms the analogy between partially saturated karst flow and chemical transport, exemplifying the compatibility of the CTRW-PT model for this purpose. Within the specific context of the Disnergschroef karst system, these findings highlight the predominance of slow diffusive flow over rapid conduit flow. The agreement between measured and simulated data supports the proposed analogy between partially saturated karst flow and chemical transport; it also highlights the potential ability of the anomalous transport framework to further enhance modeling of flow and transport in karst systems.

Dan Elhanati, Nadine Goeppert, and Brian Berkowitz

Status: open (until 17 May 2024)

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Dan Elhanati, Nadine Goeppert, and Brian Berkowitz

Data sets

CTRW simulations of karst aquifer discharge response to rainfall D. Elhanati and B. Berkowitz https://zenodo.org/doi/10.5281/zenodo.10635639

Dan Elhanati, Nadine Goeppert, and Brian Berkowitz

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Short summary
A continuous time random walk framework was developed to allow modeling of a karst aquifer discharge response to measured rainfall. The application of the numerical model yielded robust fits between modeled and measured discharge values, especially for the distinctive long tails found during recession times. The findings shed light on the interplay of slow and fast flow in the karst system, and establish the application of the model for simulating flow and transport in karst systems.