The Importance of Salty Groundwater in the Supply of Thalassotherapy: The Case of Portugal

Thalassotherapy is a balneotherapy activity with a wellness and therapeutic character, using salty water captured at sea. That activity is very similar to thermalism, which uses natural mineral water (NMW) captured in aquifer systems. In Portugal, thermalism is a well-established activity, and for a medical spa to be in operation, there is a legal requirement to have two specific professionals: a medical doctor—Clinical Director—and a hydrogeologist—Technical Director (TD). The exploitation of the NMW is the responsibility of the TD, a professional with know-how in the field of hydrogeology. Thus, this chapter presents an introduction with some fundamental concepts about thermalism and thalassotherapy, generic aspects of those activities in Portugal, and their objectives. Methodological elements are presented, followed by the main results and interpretations, with the physic-chemical characteristics of Portuguese NMWs; of very salty special groundwaters, not licensed as NMW; and sea and ocean waters. Finally, the main conclusions and several considerations are presented, in the sense that the practice of exploiting salty groundwater, in the proximity of the sea, will be a new field for the activity of hydrogeological professionals, provided that they are classified as NMW, to use in the thermalism activity.