The Gotthardreuss rises in the Gotthard massif, emerging from Lago di Lucendro (reservoir built in 1947; elevation 2,131 m) in the canton of Ticino and passing into the canton of Uri below the Brigghubel (1,898 m).

The Furkareuss rises east of Furka Pass (2,429 m), early joined by the Blaubergbach (sourced by two mountain lakes