Effect of precipitation and river Savinja on thermal water quantity status in Laško

Thermana Park Laško je eno izmed večjih središč zdraviliškega turizma v Sloveniji, v katerem že od rimskih časov izkoriščajo termalno vodo. Vzrok za pojav termalne vode na tem območju je geotermalni polzaprt vodonosnik, ki se nahaja znotraj anizijskega (srednje triasnega) dolomita Posavskih gub. Za potrebe term imajo od leta 2015 koncesijsko uredbo, da lahko črpajo vodo iz vrtine K-1/72, medtem ko K-2/95 služi za rezervo, V-7/67 pa kot opazovalna vrtina. Obravnavani podatki obsegajo obdobje med januarjem 2017 in aprilom 2022, ki sem jih primerjala s podatki iz istega obdobja s hidrološke (vodostaj in pretok Savinje) in meteorološke (količina padavin in snežna odeja) postaje v bližini zdravilišča. Na terenu sem s toplotno kamero našla tri subtermalne izvire na vzhodnem bregu Savinje, s temperaturami med 18 °C in 21 °C. Korelacija, avtokorelacija in navzkrižna korelacija podatkov iz monitoringa so pokazale pozitivno korelacijo med črpalno količino in temperaturo v K-1/72 ter negativno med črpalno količino in gladino podzemne vode v K-1/72. Cikli temperatur, dolgi nekaj mesecev, so sezonsko pogojeni – najbolj izrazito je nihanje temperature Savinje in V-7/67 (12-mesečni cikel) ter 8- do 9 mesečna nihanja gladin podzemne vode v K-2/95 in V-7/67 in vodostaja Savinje, ki so posledica stalnih deževnih obdobij med aprilom in junijem. Največ ciklov je na urni ravni, ki predstavljajo fazne zamike zaradi tlačnega vpliva. Nekatere korelacije, kot sta gladina podzemne vode in pretok v K-1/72, kažejo trenutne odzive, medtem ko se gladine podzemne vode v vrtinah K-2/95 in V-7/67 na spremembe vodostaja Savinje odzivajo z 2- do 3-urnim zamikom, glede na to ali je nizek ali visok vodostaj. Ugotovitve potrjujejo, da ima termalna voda na območju Laškega stabilno temperaturo, vodonosnik je visoko odziven na zunanje vplive (v razponu nekaj ur), nanj pa vplivajo tako sprememba vodostaja Savinje, kot tudi padavine in snežna odeja, ki se najbolj odraža v spremembi gladine podzemne vode.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