LAUSR

Article presents results of long-period observations made in the most interesting and perspective geothermal area of Poland. Moreover, Cieplice is one of the oldest spa resort in Poland where thermal waters are used for treating purposes for centuries. That is the only one region in Poland with geothermal waters in granitic rocks and this can be interesting for international readers. The region of Jelenia Góra-Cieplice has been considered a prospective area of geothermal water occurrence for many years. The earliest evidence of balneological use of these waters dates from the thirteenth century. Currently, they are being used for therapeutic purposes, and since 2014 also for recreation. The character of changes in intake discharge, water temperature and wellhead pressure observed in 1956–2019, as well as calculations of specific values (the mean, the minimum, the maximum and the standard deviation) have demonstrated considerable diversity and significant variation in these operating parameters. The main cause of changes in these parameters is changing intake operation conditions. Currently, thermal waters are being extracted chiefly from the deepened borehole C-1. Increased extraction from this intake has resulted in decreases in the temperature of thermal water from springs and borehole C-2 and a decline in their discharge or even the disappearance of their outflow. The exploitation of borehole C-1 in such conditions has also caused a drop in water pressure at its head (from 0.49 to 0.34 MPa) accompanied by an increase in water temperature (from 58 to 82 °C). The increase in water temperature is indicative of the presence of deep circulation waters in this intake. Based on the results of long-term (1963–2018) physico-chemical analyses of waters from particular intakes and deep boreholes, dominant chemical types have been distinguished: Na-HCO 3 –SO 4 and Na–SO 4 –HCO 3 , containing fluorides and silica. By using chemical geothermometers, deposit temperatures of Cieplice thermal waters have been estimated (111–138 °C). The obtained results were verified by analysing the degree of saturation of these waters with selected rock-forming minerals by means of GeoT application. The deposit temperature estimated by modelling is c. 123 °C.