Allen Wei LIU^1,*, Anton BRANCELJ^1,2 & Mihael BRENČIČ^3,4
1Department of Freshwater and Terrestrial Ecosystem Research, National Institute of Biology, Ljubljana, Slovenia
²University of Nova Gorica, Nova Gorica, Slovenia
³Department of Geology, Faculty of Natural Sciences and Engineering, University of Ljubljana, Ljubljana, Slovenia
⁴Department of Hydrogeology, Geological Survey of Slovenia, Ljubljana, Slovenia
^*Corresponding author. Phone: +38670344830; E-mail address: allen.wei.liu@nib.si

THE HYDROCHEMICAL RESPONSE OF CAVE DRIP WATERS TO DIFFERENT RAIN PATTERNS (A CASE STUDY FROM VELIKA PASICA CAVE, CENTRAL SLOVENIA)

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Data on temperature and water discharge from four permanent drips (VP1-VP4) were logged since June 2006 at one hour intervals within the Velika Pasica Cave, located in central Slovenia south of Ljubljana. In order to clarify the hydrochemical response of drip water to the water supplement regime, Drips VP1 and VP2 were selected for detailed analyses by monitoring the response of electrical conductivity (EC) and major ions to different rain events in 2011 and 2012. Two types of rainfall can be classified: “diffuse rainfall” and “concentrated rainfall”, and they affected the variation of electrical conductivity (EC) differently. It had two main characteristics at VP1: i) it had an obvious response to the dilution effect whenever the intensive rainfall occurred; ii) After the fast flow from concentrated rain events, it had a process of slow flow dissolution, with decreased EC; while during the diffuse rain events it could arrive at the dissolution equilibrium, rising to a stable EC. While due to the seepage flow at VP2, the piston effect dominated there. Meanwhile, the Mg/Ca ratio in the cave drip water showed a distinct pattern over time, influenced by the prior calcite precipitation (PCP) effect and the retention time, which was affected by different rain patterns. The precipitation regime is one of the principal impacts on drip water hydrochemistry, but other factors should be considered in future studies.