​Despite all the difficulties related to the reactive character of the water and gas discharges, geochemical surveillance of active volcanoes is an important part of any monitoring strategy and a relevant addition to other methods. Worldwide there are numerous mineral and thermal waters discharges spread in active volcanic regions, and since the 16th century settlement of the Azores archipelago there are historical references to these waters. Nevertheless, and despite the early recognition of the valuable contribution of hydrogeochemistry to volcanic surveillance programmes, studies in the Azores are still underdeveloped. With the current project the lack of data on the mineral and thermal waters of the Azores will be fulfilled, by (1) recording all historical data, (2) establishing the geological and hydrogeological setting of the discharges, (3) sampling these waters to investigate major, minor and trace elements, as well as the isotopic signatures, and (4) modelling the chemical evolution of the waters and the effects of CO₂ and H₂S added to selected samples.

As water chemistry will be characterized also in a temporal basis, results will led to the geochemical baseline of the sampled waters, excluding anthropogenic contributions, which is valuable contribution toward volcanic surveillance and to protect these resources.