What is thermal water?
Thermal water is groundwater that emerges from a natural spring or a borehole at at least 20 °C — that is the definition customary in Germany and Austria. The warmth comes from the depths: the further the water penetrates into the earth's interior, the more it heats up and the more minerals it dissolves out of the rock. In the Lower Bavarian spa triangle, for instance, the water comes from 1,000 to 2,000 metres depth; the springs of Bad Griesbach lie at around 1,500 metres.
Why the mineralisation makes the difference
Thermal water is never merely warm water. On its way through the rock it takes up dissolved substances — sulphur compounds, brine (common salt), iodine, carbonic acid or radon — and this load determines the character of the spring. Sulphur water is classically used for rheumatism and joint complaints, brine for airways and skin, iodine-rich springs for circulatory and metabolic concerns. A place receives a healing-spa designation only when its spring demonstrates a defined mineralisation and the effect has been assessed by balneology.
Thermal bath, thermal spa, healing spa — the terms
A thermal bath is the bath as a building and an experience — pools, saunas, rest worlds. A thermal spa is any bath that carries genuine thermal water. A healing spa is a state-awarded designation for the whole place: it presupposes recognised healing springs, cure infrastructure and ongoing quality controls. The fine distinction is worth it when booking: “wellness thermal bath” can also mean heated tap water — whoever seeks the effect of the depths watches for the term thermal or healing water.
Thermal water in a spa hotel
The royal class is houses with a thermal spring of their own, in which the healing water flows directly into the house's own bath — in the Rottal spa triangle (Bad Füssing, Bad Griesbach, Bad Birnbach) this combination of hotel and house spring is a regional speciality. The second variant is the neighbourhood: hotels within walking distance of a large local thermal bath combine the personal spa format in the house with the variety of pools in the thermal bath. Both models have their appeal; what is decisive is that genuine thermal water is in play.
