Anomalous behaviour of specific electrical conductivity at a karst spring induced by variable catchment boundaries: the case of the Podstenjšek spring, Slovenia

Citation

Material Information

Title:
Anomalous behaviour of specific electrical conductivity at a karst spring induced by variable catchment boundaries: the case of the Podstenjšek spring, Slovenia
Series Title:
Hydrological Processes
Creator:
Ravbar, Nataša
Engelhardt, Irina
Goldscheider, Nico
Publication Date:
Language:
English

Subjects

Subjects / Keywords:
Karst Aquifer ( local )
Spring Hydrograph ( local )
Chemograph ( local )
Variable Catchment Boundary ( local )
Numerical Modelling ( local )
Discrete‐Continuum Model ( local )
Genre:
serial ( sobekcm )

Notes

Abstract:
Anomalous behaviour of specific electrical conductivity (SEC) was observed at a karst spring in Slovenia during 26 high‐flow events in an 18‐month monitoring period. A conceptual model explaining this anomalous SEC variability is presented and reproduced by numerical modelling, and the practical relevance for source protection zoning is discussed. After storm rainfall, discharge increases rapidly, which is typical for karst springs. SEC displays a first maximum during the rising limb of the spring hydrograph, followed by a minimum indicating the arrival of freshly infiltrated water, often confirmed by increased levels of total organic carbon (TOC). The anomalous behaviour starts after this SEC minimum, when SEC rises again and remains elevated during the entire high‐flow period, typically 20–40 µS/cm above the baseflow value. This is explained by variable catchment boundaries: When the water level in the aquifer rises, the catchment expands, incorporating zones of groundwater with higher SEC, caused by higher unsaturated zone thickness and subtle lithologic changes. This conceptual model has been checked by numerical investigations. A generalized finite‐difference model including high‐conductivity cells representing the conduit network (“discrete‐continuum approach”) was set up to simulate the observed behaviour of the karst system. The model reproduces the shifting groundwater divide and the nearly simultaneous increase of discharge and SEC during high‐flow periods. The observed behaviour is relevant for groundwater source protection zoning, which requires reliable delineation of catchment areas. Anomalous behaviour of SEC can point to variable catchment boundaries that can be checked by tracer tests during different hydrologic conditions. Copyright © 2011 John Wiley & Sons, Ltd.
Original Version:
Hydrological Processes, Vol. 25, no. 13 (2011-02-01).

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University of South Florida Library
Holding Location:
University of South Florida
Rights Management:
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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