The nominal source of the Jochberger Ache lies at above sea level on the Thurn Pass. A few of its early tributaries are, however, larger and have a greater discharge. The most important is the Trattenbach which starts as a trickle from a high cirque at about above sea level between the mountains of the Zweitausender and the Rossgruberkogel south of the Kleiner Rettenstein, and is fed by several other springs before it joins the Jochberger Ache.