Thermana Park Laško is one of the biggest health resorts in Slovenia, where thermal water is being used since the Roman era. The appearance of thermal water is connected to the geothermal leaky aquifer, which is settled in the Anisian (Middle Triassic) dolomite of western Sava folds. Since 2014 the concession for water usage was given to the spa for pumping water from well K-1/72, which is the most active, as well as occasionally used K-2/95 and monitoring well V-7/67. The data was monitored from January 2017 to April 2022. Data was compared to the data from the hydrological and meteorological station nearby, which provided information about the water level, flow, precipitation and snow cover. In the field three thermal springs were located at the eastern riverbank of the Savinja river, with temperatures ranging from 18 °C to 21 °C. Correlation, autocorrelation and cross correlation of the monitored data have shown positive correlation between pumping quantity and temperature in K 1/72 and negative correlation between pumping quantity and groundwater level in K 1/72. Monthly cycles of temperature are seasonally – oscillations of the temperature of Savinja and V-7/67 are clearily noticed every 12 months, as well as 8 and 12 months oscillations of the groundwater level in K-2/95, V-7/67 and the Savinja water level, which are the consequence of constant rainy months (April – June). Most of the cycles are seen at an hourly level, representing the phase lags related to the pressure effect. Correlations, such as groundwater level and pumping quantity in K-1/72 are showing immediate response, whereas the groundwater levels in wells need 2 to 3 hours to respond to the Savinja water level changes, depending on, whether the water flow is low or high. In conclusion, the thermal water in Laško area has a stable temperature, the aquifer is highly responsive to external influences (in the span of a few hours) and is affected by the changes of Savinja water level, as well as precipitation and snow cover, which is mostly visible in the groundwater level changes.
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