The Aschauer Ache rises at the foot of the Großer Rettenstein and then flows to Kirchberg, continuing to Reith bei Kitzbühel before discharging into the Kitzbühler Ache near St. Johann in Tirol.
During the August 2002 European flood, parts of St. Johann in Tirol were affected by the flood due to high water levels of Kitzbühler Ache and Reither Ache.