The hydrogeology

General information on the thermal springs
The thermal springs of Leukerbad have been used without interruption since Roman times. In Leukerbad 8 springs or groups of springs are currently used for balneary or energetic purposes. In total, approx. 65 thermal springs have been entered in a cadastre. They range from lukewarm percolation water outlets to the 51°C warm St. Lorenz spring, which has a very constant yield of approx. 900 l/min.

The thermal springs partly come to the surface directly from solid spathic limestone and more rarely from clay schist. Various springs have to make their way from the rocky thermal aquifer through a thick cover of unconsolidated material, such as the St. Lorenz spring. The total thermal water yield in Leukerbad is estimated to amount to approx. 3000 l/min of unmixed thermal water.

Composition of the thermal water
All of the thermal water in Leukerbad originates from one thermal aquifer and comprises calcium sulphate water with a slightly increased sodium, strontium and iron content, and a remarkable fluoride content. It also has a high content of dissolved solids (1800-2000 mg/l). The thermal water partly contains a dark brown suspension which originates from the Aalenden schist which it flows through. The bright russet colour of the mud ("Fango"), which is typical of many springs, is caused by its high iron content. All thermal springs have a certain admixture of cold water (9 - 40%).

Origins of the thermal water
Its long journey starts east of Leukerbad in the region between the Majing- and Torrenthorn. At lake Wyss and lake Schwarz, at approx. 2300 to 3000 m.a.s.l., rainwater infiltrates and penetrates into the rock mass through steep dipping joint systems to a depth of approx. 500 m below sea level. The water becomes saturated with calcium and sulphate in the vicinity of Triassic gypsum, and rises as thermal water as it becomes warmer, and finally surfaces in the numerous springs in Leukerbad. The water definitely travels along subterranean routes for more than 40 years, as was detected by means of tritium measurements. To what extent the crystalline rock of the Aar massif also comes into contact with the subterranean route is still a bone of contention.

Earthquakes, changes in precipitation and not least construction activities may influence the yield and the properties of the springs.