Poland belongs to the countries with limited waters intended for drinking resources. To meet this problem, the Management Board of Geotermia Mazowiecka SA carries out activities to determine the possibilities of using exploited geothermal waters other than energy purposes. In addition to energy, the geothermal water is used for recreation and balneotherapy in “Termy Mszczonów” and for the production of drinking water for the local water supply system. Some water needs to be discharged into surface watercourses due to a lack of coherence of heating and water supply needs. For recognizing this problem innovative research project entitled: “The development of a method for injecting after energy-used geothermal waters into selected geological structures” was prepared and implemented as part of the Regional Operational Program of the Mazowieckie Voivodship for 2014–2020 (Priority Axis: Research and development activities of enterprises). This project has resulted in the launch of the installation pumping excess water to the quaternary sandy leyer. Based on the results from the first year of operation of the project, it can be assumed that it is possible to achieve nearly 100% reduction of water discharge and, consequently, the full use of producted geothermal waters. In summary, it can be stated that the geothermal plant in Mszczonów is a unique installation not only on the Polish but also international scale. The proof of this is not only the scale of rational use of water for energy purposes (cooling from 41°C to about 17°C), but also their development in other areas, for example in “Termy Mszczonów” and for the production of waters intended for drinking. The article presents the results of the first year (2019) of operation of the water injection system. During this period, in cooled water discharged into surface watercourse nearly 50% reduction was achieved.

The aim of the presented work was an attempt to verify the geothermal conditions in the Polish Lowlands (Lower Jurassic and Lower Cretaceous reservoir) based on new geological information. The paper presents geothermal conditions in the Polish Lowlands according to the state of recognition at the end of 2022 in order to update the hydrogeothermal conditions in selected regions. Based on the scientific and research works published so far as well as numerous geothermal investments, and geological information from twenty-three new exploratory drilling events performed in the years 2000–2022 (nineteen of which were performed/documented after 2006), the authors undertook to update forecasts of the top surface of Lower Jurassic and Lower Cretaceous formations, the total thickness of these formations and the potential discharge of wells. The analysis was performed using the QGIS Desktop 3.24.1 software, a cross-platform and free open-source geoinformation software application (GIS ) that enables the viewing, editing and analyzing of spatial data and the creation of maps. The correction covered the course of the isolines on all six analyzed maps. The presented analysis made it possible to make a spot correction of the forecasted course of the isoline in relation to the maps published earlier in the Atlas of geothermal resources in the Polish Lowlands. Mesozoic formations developed in 2006, edited by Wojciech Górecki. Information obtained from newly drilled geothermal boreholes enabled the local correction of the forecasted values of individual parameters while maintaining the general trend.