Further on the young Isar is supplied water by the Birkkarbach, which has its source at the foot of the highest mountain of the Karwendel, the Birkkarspitze and the Moserkarbach.
Videre får Isar vand fra Brikkarbach, som har sin kilde ved foden af det højeste bjerg i Karwendel, Birkkarspitze og Moserkarbach.