 Thermal springs in the Alps are exclusively fed by meteoric water which on average circulates to a depth of at least 2 km  On average the contributing area of springs in the Alps is 0.6 km 2 and the thermal footprint is 6 km 2  Comparison with North American orogens indicates that hydrothermal activity is highest in orogens with high relief or undergoing extension

No abstract

The extent of deep groundwater flow in mountain belts and its thermal effects are uncertain. Here, we use a new database of discharge, temperature and composition of thermal springs in the Alps to estimate the extent of deep groundwater flow and its contribution to the groundwater and heat budget. The results indicate that springs are fed exclusively by meteoric water and make up 0.13% of the total groundwater budget. Spring water circulates on average to a depth of at least 2100 m. The net heat extracted from the subsurface equals 1.5% of the background heat flow, which equals an average thermal footprint for springs of 6 km2. Cooling by downward flow and heating by upward flow are estimated as approximately 6.5% and 5.0% of the background heat flow, respectively. Compared to orogens in North America the Alps have a relatively high amount of hydrothermal activity.