The 11 natural springs of mineral and CO2-rich waters studied are located in the region of Scuol-Tarasp in the Lower Engadine (Canton Grisons, Switzerland ). Known since the Middle Ages, the Scuol-Tarasp waters are being successfully used for medicinal and healing purposes. 4 other springs in Canton Grisons (Val Sinestra, St Moritz, Rhäzüns and Rothenbrunnen) were also considered on account of particular similarities with those of Scuol-Tarasp.
The spring outflows are located in the well-known Engadine tectonic window, in which Pennine Bündner-schiefer ("Schistes lustrés") and ophiolites are ovethrusted by Austroalpine Nappes, which are generally composed of sedimentary rocks.
27 sites (springs, wells and rivers) were sampled during a complete hydrological cycle (1984-1985). The sampling programme was carried out at 4 regular time intervals in nearly every case, excepted for particularly unfavourable climatic conditions. The following physical-chemical parameters were measured on site: total alkalinity, CO2 content, pH, conductivity, temperature and flow rate.
14 parameters were analysed (major cations and anions), permitting the calculation of the ionic balance and thus providing a check on the quality of the analyses. Boron, silica and arsenic were also analysed in many instances.
165 isotopic analyses (tritium, deuterium, 18O, 18O in sulphates, 34S, 13C and 14C) were carried out in a number of specialised laboratories, and were supplemented by special analyses of gas from vents ("mofettes") and from mineral springs (complete gas analyses, 13C, noble gases, and, in some cases, helium and helium isotopes).
