Terminologies and characteristics of natural mineral and thermal waters in selected European countries

This study discusses 1) the national legislative frameworks, terminologies, and criteria for the recognition of natural mineral waters and thermal waters in selected European countries (Austria, Bosnia and Herzegovina, Denmark, France, Hungary, Iceland, Italy, Lithuania, Poland, Portugal, Romania, Serbia, Slovenia, and Spain), and 2) it provides a first extensive multi-national overview of hydrogeological and hydrogeochemical characteristics of numerous water sources from those regions. Natural mineral waters are well defined and regulated in the European Union by the Directives 2009/54/EC and 2003/40/EC that are implemented by national law regulations. In contrast, no legal definition exists for thermal waters on an EU level and national definitions commonly differ or are not present. Defining thermal waters by water temperatures of at least 20 °C at the outlet is commonly found (6 out of 15 countries), but other definitions like considering the difference to the average air temperature are also present. Furthermore, no definitions on a national level are quite frequent (5 out of 15 countries), those countries preferentially refer to expert recognitions. We considered 678 natural mineral waters and 2,390 thermal waters in this study and collected information on practical use, hydrogeological settings and hydrogeochemical conditions. The comparison of the datasets shows commonalities like a predominance porous aquifers, especially sandy aquifers, and sedimentary carbonate rock aquifers (limestone, dolomite, chalk). Furthermore, natural mineral waters commonly show TDS contents of less than 1 g/l and alkaline-earth-HCO3 water types. Surprisingly, 21 % of the considered sources bear water temperatures above 20 °C and could be considered as thermal waters as well. Thermal waters – the majority (above 30 °C) is found in Hungary - usually show water temperatures between 20 and 70 °C and TDS contents between 1 and 14.5 g/l. The hydrogeochemical properties show a larger variation in contrast to natural mineral waters, but Na-(HCO3, Cl) waters seem to be most commonly found.