When the Great Aletsch glacier was much more mighty than today, the Lake Märjelen presented a constant threat for the local population. In order to mitigate the lake outbursts, a small channel was dug in 1828 and large one in 1829. The desired success, however, was limited. Rather, the water flowing through the channels caused increasingly flooding in the Fiesch valley. Another attempt to reduce the water level and to reduce definitely the threatening by the Lake Märjelen was undertaken between 1889-1894, however at much deeper water level. A 583 m long discharge tunnel was built through the rock in direction to the Fiesch valley. This underground spillway came but once operative, namely in 1896. Water was flowing through the tunnel during six weeks. Since then, the water level of the lake has never reached the bottom of the tunnel entrance. The tunnel outflow can be seen near the Märjelenalp (Märjelenwang) on the way to the Fiesch valley. The tunnel entrance is no longer visible; it is below the water surface of the artificial lake Vordersee, damned in 1988.