Long-term observation of a low-temperature hydrothermal system (Campiglia, Central Italy).

The Campiglia low-temperature geothermal system covers an area of about 30 km2 in southern Tuscany (Italy), only 20 km southwest of the Larderello geothermal field. The region is characterized by a main thermal aquifer (densely fractured carbonate-evaporitic Mesozoic formations) that is generally confined, but does crop out in some places. The thermal springs emerge on the boundaries of these outcrops. Seven water-points (springs and wells) in the geothermal system were monitored for three years. All of the springs revealed seasonal variations in flow rate, but constant chemical and isotopic compositions. Two of the wells, on the contrary, revealed strong variation in water composition. On the basis of the geohydrological and geochemical data, we have identified two possible water sources for the hydrothermal system and hypothesized the flowpaths followed by the waters feeding the various water-points.