| Abstract: | The Malenščica spring is an important source of drinking water for approximately 21,000 inhabitants in the municipalities of Postojna and Pivka. In addition to the Unica spring, the Malenščica spring is one of two major karst springs on the southern edge of the Planina karst polje in the southwest of Slovenia. Both springs are recharged by a complex karst system, characterized by an exchange between surface and underground flow.
In determining the characteristics of karst springs, we used a method of tracing with natural traces, which includes measuring the natural properties of water such as flow rate, temperature, electrical conductivity and chemical composition of water at different points within the karst aquifer, and measure these changes over time at different hydrological conditions. There were four sets of data that were previously collected and properly processed to study and process the topic of the master's thesis.
The first group includes data on the measurement of electrical conductivity at 30-minute intervals at both springs and sinking streams Pivka and Rak in their recharge area in the period from October 15, 2016 to January 4, 2017 when hydrological conditions varied from low to high water levels and then again to a drier period at the end of year 2016. The second group includes data from periodic basic chemical analysis and analysis of metals for the Malenščica spring for a longer period, from April 17, 2007 to Octoober 10, 2017. The third group of data presents the results of chemical and microbiological analysis in both springs and sinking streams during the flood wave in the period from September 7, 2017 to October 3, 2017. The fourth set of data, collected from all four locations, gathered the results which were obtained during the preparation of the master's thesis, to perform detailed sampling and chemical analysis during the flood wave for the period between May 10, 2019 and May 15, 2019. Comparison of different data sets for the four sampling points (Malenščica, Unica, Rak and Pivka) enables a better understanding of the relationships between different parts of the recharge area and of changing their proportions when recharging both springs under different hydrological conditions. Based on the determination of the time delays between the peaks (maximums) or troughs (minimums) of the electrical conductivity curves, we also estimated the apparent groundwater flow rates between sinking streams and springs. Based on the comparison of changes in physical, chemical and microbiological parameters for different precipitation and hydrological conditions of springs and water flows in their recharge area, we could infer about the characteristics of groundwater flow in the studied karst aquifer. |
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