The accelerated loss of the Great Aletsch glacier in the 20th century led to a decline in the lake Märjelen. The lake was divided by a terrain threshold into two basins: in the larger and deeper lake at the edge of the glacier, the glacier lake or Hintersee, and in the shallower Vordersee, located near to the huts of the Märjelenalp. The Vordersee was enlarged artificially by a dam in 1988 in the framework of the "Märjelen project" and collects the spring water from the area of the Galtjinen sources (Galkina) below the Strahlhorn. The water is directed from the lake through the newly built, one kilometer long Tälligrat tunnel into a reservoir. From there a water pipe with irrigation water leads to Lax, Martisberg, Goppisberg, Riederalp and Oberried. Another pipe leads into a reservoir near the Laxeralp where the water is made potable. From there the drinking water flows to another reservoir and finally supplied to the aforementioned villages. The Tälligrat tunnel now serves as well as shortcut for walks in the area of Märjela and as supply road to the dammed Vordersee and the Berghaus "Gletscherstube".