Thermomineral Water and Geothermal Energy - Hydrogeology: Objectives, Methods, Applications - page 79

C HAPTER A10
Thermomineral Water and
Geothermal Energy
1 DEFINITION
Hot springs have been known since the ends of time and have been used
since Antiquity for baths. Aside from their temperature, these waters
generally have very particular characteristics: gases, smells, mineral content.
Indeed, their increased temperature and pressure allows the dissolution
of salts and gases which enrich the water in an unusual way. This water
is then called thermomineral water. Its unusual properties are used in the
hydrotherapy industry. Water, or the mud associated with it, are used
therapeutically for bathing or in drinks.
There is no precise definition for thermal waters. Although the
etymology of the word refers to temperature, its use in hydrotherapy calls
upon the physical and chemical properties of the water. The defi nition
given in the French dictionary of hydrogeology (Castany & Margat, 1977)
is: “underground water which is naturally warm at its emergence (spring,
artesian well) and is therefore usable for particular needs: hydrotherapy,
heating.”
The concept of temperature is itself delicate to evaluate given that water
can appear more or less hot with respect to its environment depending
on the seasons. The term thermal is used only if the water temperature
is a few degrees higher than the average temperature of springs located
at the same elevation. The concept of mineralisation is just as diffi cult to
determine, as can be seen in the special case of saline coastal springs, whose
properties are in fact linked to the contamination of continental aquifers by
sea water. Similarly, a high mineral content can originate from the leaching
of evaporites (sulfate or chloride enrichment).